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Photosynthesis is a process that uses solar energy to fix CO2 in the air and converts it into sugar, and ultimately powers almost all life activities on the earth. C3 photosynthesis is the most common form of photosynthesis in crops. Current efforts of increasing crop yields in response to growing global food requirement are mostly focused on improving C3 photosynthesis. In this review, we summarized the strategies of C3 photosynthesis improvement in terms of Rubisco properties and photorespiratory limitation. Potential engineered targets include Rubisco subunits and their catalytic sites, Rubisco assembly chaperones, and Rubisco activase. In addition, we reviewed multiple photorespiratory bypasses built by strategies of synthetic biology to reduce the release of CO2 and ammonia and minimize energy consumption by photorespiration. The potential strategies are suggested to enhance C3 photosynthesis and boost crop production.

Issues surrounding soil fertility are fundamental to the productivity and sustainability of diverse agricultural production systems around the world. In developed economies, intensive fertilization is a chief economic, energetic, and environmental cost to crop production, depleting finite resources and causing massive pollution through leaching and runoff. In developing economies where access to, and utilization of soil amendments are rare, degraded soils with low nutrient availability are a primary constraint to yields. The most common challenges surrounding soil fertility in most production systems primarily involve nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), sulfur (S), iron (Fe), and zinc (Zn). A chief component of a robust and pragmatic solution to these soil fertility issues lies in the development of more nutrient-efficient crops. In pursuit of this objective, root phenotypes that improve the efficiency of soil exploration and acquisition of resources offer exceptional opportunities as breeding targets. Natural variation for root phenotypes can have significant effects on soil resource extraction by modifying the placement of roots in soil domains where limiting resources are most available, improving the metabolic efficiency of soil exploration, as well as altering the radial and axial transport of resources. In this chapter, we review root anatomical and architectural phenes that have demonstrated benefit for enhancing acquisition of the most commonly limiting nutrients, and advocate for the consideration of root phenotypes in breeding programs focused on developing crops with greater nutrient efficiency.

Background For achieving long-term sustainability of intensive agricultural practices, it is pivotal to understand belowground functional stability as belowground organisms play essential roles in soil biogeochemical cycling. It is commonly believed that resource availability is critical for controlling the soil biodiversity and belowground organism interactions that ultimately lead to the stabilization or collapse of terrestrial ecosystem functions, but evidence to support this belief is still limited. Here, we leveraged field experiments from the Chinese National Ecosystem Research Network (CERN) and two microcosm experiments mimicking high and low resource conditions to explore how resource availability mediates soil biodiversity and potential multi-trophic interactions to control functional trait stability. Results We found that agricultural practice-induced higher resource availability increased potential cross-trophic interactions over 316% in fields, which in turn had a greater effect on functional trait stability, while low resource availability made the stability more dependent on the potential within trophic interactions and soil biodiversity. This large-scale pattern was confirmed by fine-scale microcosm systems, showing that microcosms with sufficient nutrient supply increase the proportion of potential cross-trophic interactions, which were positively associated with functional stability. Resource-driven belowground biodiversity and multi-trophic interactions ultimately feedback to the stability of plant biomass. Conclusions Our results indicated the importance of potential multi-trophic interactions in supporting belowground functional trait stability, especially when nutrients are sufficient, and also suggested the ecological benefits of fertilization programs in modern agricultural intensification.

Crop models can support the design of smart crop management practices. The Farquhar-von Caemmerer-Berry (FvCB) model is increasingly being used in these models for quantifying leaf photosynthesis. Nitrogen (N) is required for many functional machineries of photosynthesis, thus relationships between FvCB-model parameters and leaf N content (LNC) should be established. We conducted combined gas exchange and chlorophyll fluorescence measurements on fully expanded leaves of two C3 crops, rice (Oryza sativa) and wheat (Triticum aestivum), and two C4 crops, maize (Zea mays) and sorghum (Sorghum bicolor), grown under three N levels. Photosynthetic parameters were estimated and linear relationships between these parameters and LNC were quantified in both C3 and C4 crop types. The efficiency of converting incident light into linear electron transport for C3 crops or into ATP production for C4 crops showed a weak increase with LNC. The maximum electron transport rate (Jmax) for C3 crops or the maximum ATP production rate (Jmax,atp) for C4 crops significantly increased with LNC. The increase in Rubisco carboxylation capacity (Vcmax) with LNC was significantly higher in C3 than in C4 crops. Triose phosphate utilization for C3 crops and PEP carboxylation capacity (Vpmax) for C4 crops increased significantly with LNC as well. Except for Jmax at 21% O2 and Vcmax of C3 crops, there was no significant difference among crops in the relationship between estimated photosynthetic parameters and LNC. The tight associations of photosynthesis parameters with LNC were discussed in view of decision making on N management in the context of smart farming.

Key message Correlations between morphological traits of cabbage rosette leaves and heads were found. Genome-wide association studies of these traits identified 50 robust quantitative trait loci in multiple years. Half of these loci affect both organs. Abstract Cabbage (Brassica oleracea var. capitata) is an economically important vegetable crop cultivated worldwide. Cabbage plants go through four vegetative stages: seedling, rosette, folding and heading. Rosette leaves are the largest leaves of cabbage plants and provide most of the energy needed to produce the leafy head. To understand the relationship and the genetic basis of leaf development and leafy head formation, 308 cabbage accessions were scored for rosette leaf and head traits in three-year field trials. Significant correlations were found between morphological traits of rosette leaves and heads, namely leaf area with the head area, height and width, and leaf width with the head area and head height, when heads were harvested at a fixed number of days after sowing. Fifty robust quantitative trait loci (QTLs) for rosette leaf and head traits distributed over all nine chromosomes were identified with genome-wide association studies. All these 50 loci were identified in multiple years and generally affect multiple traits. Twenty-five of the QTL were associated with both rosette leaf and leafy head traits. We discuss thirteen candidate genes identified in these QTL that are expressed in heading leaves, with an annotation related to auxin and other phytohormones, leaf development, and leaf polarity that likely play a role in leafy head development or rosette leaf expansion.

Intercropping creates a heterogeneous canopy and triggers plastic responses in plant growth and structural development. In order to quantify the effect of planting pattern, strip width and row position on the structural development and light capture of maize and soybean in simultaneous intercropping, both experimental and modelling approaches were used. Field experiments were conducted in 2017－2018 with two sole crops (maize and soybean) and two intercrops: Two rows of maize alternating with two rows of soybeans (2:2 MS) and three rows of maize alternating with six rows of soybean (3:6 MS). The morphological traits of maize and soybean e.g., leaf length and width, internode length and diameter, leaf and petiole declination angle in different rows and different planting patterns, and photosynthetically active radiation (PAR) above and below the canopy of 2:2 MS were measured throughout the growing season. A functional-structural plant model of maize-soybean intercropping was developed in the GroIMP platform. The model was parameterized based on the morphological data set of 2017, and was validated with the leaf area index (LAI), plant height and PAR data set of 2018. The model simulated the morphological development of individual organs based on growing degree days (thermal time) and calculated the light capture at leaf level. The model well reproduced the observed dynamics of leaf area index and plant height (RMSE: 0.24－0.70 m2/m2 for LAI and 0.06－0.17 m for plant height), and the fraction of light capture in the 2:2 MS intercropping (RMSE: 0.06－0.10). Maize internode diameter in intercrops increased, but the internode length did not change. Soybean internodes in intercrops became longer and thinner compared to sole soybean probably caused by the shading imposed by maize, and the 2:2 MS had longer internodes than the 3:6 MS, indicating the effects of strip width. Simulated light capture of maize in 2:2 MS intercropping was 35.6% higher than sole maize. For maize in 3:6 MS intercropping, the light capture of the border rows and inner row were 27.8% and 20.3% higher than sole maize, respectively. Compared to sole soybean, the simulated light capture of soybean in border rows was 36.0% lower in 2:2 MS intercropping, and was 28.8% lower in 3:6 MS intercropping. For 3:6 MS intercropping, light capture of soybean in inner rows I and inner rows II were 4.1% and 1.8% lower than sole soybean, respectively. In the future, the model could be further developed and used to explore and optimize the planting patterns of maize soybean intercropping under different environmental conditions using light capture as an indicator.

Drought poses a serious threat to crop production worldwide, and is expected particularly to affect rice production and hence food security. Given that wheat is known to tolerate drought better than rice, we compare rice and wheat (cv. Weebill) to understand the species level differences in drought adaptive mechanisms. We also compare two contrasting rice genotypes (IR64, drought susceptible, and Apo, drought tolerant) for such mechanisms under well-watered (100% field capacity, 100%FC) and water-limited (60%FC) conditions. The reduction in biomass of wheat under water limitation was smaller due to a higher rate of photosynthesis associated with maintenance of tissue turgor compared to rice genotypes. Drought caused greater inhibition of Photosystem II quantum efficiency, carboxylation efficiency, and photosynthetic capacity parameters in IR64 than in Apo. Transcript levels of photosynthesis-related genes were also significantly more repressed by water limitation in IR64, whilst the wheat genotype showed smaller reduction than Apo. Despite higher non-photochemical quenching (NPQ), a smaller increase in scavenging enzymes in IR64 resulted in more accumulation of reactive oxygen species (ROS) in 60%FC than in 100%FC compared to Apo. As a photoprotection mechanism, increased levels of NPQ resulted in lower ROS accumulation in wheat despite the similar increase in scavenging enzyme transcript levels as in Apo, signifying the importance of preventing oxidative burst for enhanced drought tolerance. In Apo, upregulation of the 9-cis-epoxycarotenoid dioxygenase 2 gene implies the use of xanthophyll pool for the ABA biosynthesis. Our data suggest that regulating photosynthesis and oxidative protection in the wheat genotype enhanced drought tolerance. Improving these traits for rice is crucial to develop drought-tolerant rice genotypes.

In nature, light is never constant, while in the controlled environments used for vertical farming, in vitro propagation, or plant production for scientific research, light intensity is often kept constant during the photoperiod. To investigate the effects on plant growth of varying irradiance during the photoperiod, we grew Arabidopsis thaliana under three irradiance profiles: a square-wave profile, a parabolic profile with gradually increasing and subsequently decreasing irradiance, and a regime comprised of rapid fluctuations in irradiance. The daily integral of irradiance was the same for all three treatments. Leaf area, plant growth rate, and biomass at time of harvest were compared. Plants grown under the parabolic profile had the highest growth rate and biomass. This could be explained by a higher average light-use efficiency for carbon dioxide fixation. Furthermore, we compared the growth of wild type plants with that of the PsbS-deficient mutant npq4. PsbS triggers the fast non-photochemical quenching process (qE) that protects PSII from photodamage during sudden increases in irradiance. Based mainly on field and greenhouse experiments, the current consensus is that npq4 mutants grow more slowly in fluctuating light. However, our data show that this is not the case for several forms of fluctuating light conditions under otherwise identical controlled-climate room conditions.

Korla fragrant pear (Pyrus sinkiangensis Yü) depends on cross-pollination by honeybees (Apis mellifera) but may suffer from low honeybee visitation. We assessed whether honeybee abundance and visitation frequency are enhanced by using synthetic Nasonov gland pheromone (NGP), which is naturally produced by worker bees to stimulate the aggregation of bees to food resources or nesting sites. The response of honeybees to synthetic NGP was firstly assessed using Y-tube olfactometer tests in the laboratory, and subsequently in the field, by placing NGP lures on Korla fragrant pear trees in orchards with and without beehives. Honeybee abundance was assessed using coloured pan traps while honeybee visits were assessed by visual observations on pear flowers. Y-tube olfactometer tests showed a significant preference of honeybees for NGP. In pear orchards with beehives, honeybee abundance was 2.5-fold higher on trees with NGP lures than on trees without NGP, and 2.2-fold higher in orchards in which all trees contained NGP lures than in orchards without NGP lures. Such positive effects were not observed in orchards without beehives. Flower visitation by honeybees was significantly higher in trees with NGP lures than without NGP lures, irrespective of the presence (5.7-fold higher) or absence of beehives (27.6-fold higher). In mixed pear-apricot orchards, honeybee abundance was higher in pear trees with NGP lures than without lures. Our results show that NGP lures attract honeybees to flowering pear trees in monoculture pear and mixed pear-apricot orchards, and that this effect is greatest in orchards with beehives.

Data has been presented in Figs. 4 - 8 in the publication. Ten treatments have been indicated by treatment codes as "MM" for maize monocrop, "WW" for wheat monocrop, "BB" for faba bean monocrop, "PP" for pea monocrop, "MW" for maize/wheat intercrop, "MB" for maize/faba bean intercrop, "MP" for maize/pea intercrop, "BW" for faba bean/wheat intercrop, "BP" for faba bean/pea intercrop, and "WP" for wheat/pea intercrop.

In vitro-propagated potato plantlets are commonly used in potato seed tuber production. Four experiments were carried out to identify how the duration of the last in vitro phase (‘age’) before planting of in vitro-produced plantlets affects the early growth and development ex vitro, assessed 10–14 days after planting. Experiments included varying ranges in age of the in vitro plantlets at planting (10–40, 15–45, 14–28 and 14–56 days old at the moment of planting in the respective experiments) and different cultivars. Because in vitro plantlet size increases with age, the first experiment studied interactions between age and planting method. Planting ‘deep’ (the upper four visible leaves above the ground) seemed more robust than planting ‘shallow’ (all nodes/leaves above ground except the lowest two), and in later experiments, only deep planting was applied. Across experiments, plants grown from younger in vitro plantlets had smaller leaf areas 10–14 days after planting than those from older in vitro plantlets. The increase in leaf area levelled off with increasing age of the in vitro plantlets used, especially when plantlets were older than c. 28 days. Larger leaf areas 10–14 days after planting were related to the older in vitro plantlets having higher absolute growth rates after planting and a larger above-ground leaf area at planting, even though four leaves were kept above ground in all treatments. Below ground, plants from older in vitro plantlets had more stem nodes, initiated stolons earlier after planting and initiated more stolons per plant. Tuber initiation rarely occurred within 14 days after planting, but was observed in some plants from 42- and especially 56-day-old in vitro plantlets of the very early cultivar Gloria and a single plant from 56-day-old in vitro plantlets of the mid-early cultivar Bintje. The data show that planting older in vitro plantlets can enhance early leaf area growth. Plants from older in vitro plantlets also more readily initiate stolons below ground and may be more advanced in the tuber formation process, especially when from early cultivars.

The study was conducted to determine the dormancy and physiological age characteristics of diverse potato genotypes as influenced by growing altitudes and seasons for future breeding strategies and optimal patterns of use. Dormancy and sprouting characteristics have an impact on tuber production, storability and seed quality for planting and ware for consumption and the market. This study presents the results of dormancy and physiological age measurements conducted on 47 potato genotypes grown at three altitudes with three replications at each location and in two contrasting growing seasons. The seed tubers were evaluated at low altitude under darkness on moist sand storage conditions to assess their dormancy release, number of sprouts, sprout weight, sprout length and percentage tuber weight loss. Results showed significant (p

Lucerne (Medicago sativa L.) is a widely grown perennial legume worldwide which can provide high biomass and protein yields, biological N fixation, deep soil water extraction and a range of ecosystems services relevant to current and future agricultural systems. The potential to expand lucerne beyond its current cultivated areas in New Zealand, and its potential productivity across the country's contrasting climate zones, are currently unknown. To gain such insights, we estimated land suitability and spatial distribution of lucerne above-ground biomass across New Zealand lands considering contrasting growth conditions (rain-fed or irrigated for different soils types) and two simulation methods of different complexity (process- and GIS-based approaches). This aimed to assess yield-estimate spatial patterns and sensitivity to model selection for a wide range of combinations of water supply (i.e. irrigation and soil water storage) across New Zealand climate zones. For example, highly suitable areas for lucerne cultivation, were estimated in ∼21 thousand km2 when considering the exclusion of steep slopes, poor soil drainage and excess annual rainfall. The two crop-yield models were applied in response to 30 years of daily historical (1971–2000) weather data downscaled at 5 km resolution on suitable areas. Simulated average lucerne yields ranged from ∼4.5–28 t dry matter/ha per year. Simulations showed a distinct spatial pattern of yield decline from north to south, mainly in response to decreasing temperatures. Temporally, water limited yields were up to 4-fold more variable than under irrigation, depending on the degree of drought stress across different years. Results also unveiled systematic spatial patterns of model uncertainty quantified as yield sensitivity to model selection. For instance, simulated yields were most sensitive to model selection (6–31% of total variability, Ti) within high abiotic-stress environments (e.g. low temperature and limited water supply). Overall, soil type selection accounted for most of yield variability (58–78% Ti), being particularly important in warmer environments with variable seasonal rainfall regimes (e.g. northern regions). As expected, water supply (i.e. rain-fed or irrigated systems) was relatively more impactful on yield (8–20% Ti) for limited rainfall areas, where crops are most drought prone (e.g. east coast and central southern regions). Long-term regional scale comparisons of annual lucerne yield, between 30-year simulated distributions and point-based observations from the AgYields database, helped identify hotspots of yield overestimation. Such insights are useful to guide future research on high yield gap areas (e.g. southern colder and drier locations) and highlight key areas for model improvement (e.g. representation of multiple biotic stresses). Overall, our results provide a first gridded-model assessment of lucerne suitability and yield at national scale and quantify the share of variability explained by key climatic, management and methodological components in spatial analysis studies. These insights can inform future modelling efforts and support agricultural planning that considers the expansion of lucerne and other perennial legumes.

Research on diploid hybrid potato has made fast advances in recent years. In this review we give an overview of the most recent and relevant research outcomes. We define different components needed for a complete hybrid program: inbred line development, hybrid evaluation, cropping systems and variety registration. For each of these components the important research results are discussed and the outcomes and issues that merit further study are identified. We connect fundamental and applied research to application in a breeding program, based on the experiences at the breeding company Solynta. In the concluding remarks, we set hybrid breeding in a societal perspective, and we identify bottlenecks that need to be overcome to allow successful adoption of hybrid potato.

CONTEXTMillions of people living in the Eastern Gangetic Plains (EGP) of India engage in agriculture to support their livelihoods yet are income poor, and food and climate insecure. To address these challenges, policymakers and development programs invest in irrigation-led agricultural intensification. However, the evidence for agricultural intensification to lift farmers’ incomes above the poverty line remains largely anecdotal. OBJECTIVEThe main objective of this study is to use a large household survey (n=15,572; rice: 8,244, wheat: 7,328; 2017/18) to assess the link between agricultural intensification and personal daily incomes from farming (FPDI) in the rice-wheat systems of the EGP – the dominant cropping system of the region.METHODSWe use the Intensification Benefit Index (IBI), a measure that relates farm size and household size to FPDI, to assess how daily incomes from rice-wheat production change with irrigation-led intensification across the EGP.RESULTS AND CONCLUSIONSRelative to the international poverty line of 1.90 Purchasing Power Parity (PPP)$ day-1 and accounting for variations in HH size in the analysis, we found that small farm sizes limit the potential for agricultural intensification from irrigation to transform the poverty status of households in the bottom three quartiles of the IBI. The estimated median FPDI of households with intensified systems in the bottom three quartiles is only 0.51 PPP$ day-1 (a 0.15 PPP$ gain). The median FPDI increases to 2.10 PPP$ day-1 for households in the upper quartile of the IBI distribution (a 0.30 PPP$ gain). Irrigation-led agricultural intensification of rice-wheat systems in the EGP may provide substantial benefits for resilience to climatic change and food security but achieving meaningful poverty reduction will require complementary investments.SIGNIFICANCETransforming the poverty status of most smallholder farmers in the EGP requires diversified portfolios of rural on- and off-farm income-generating opportunities. While bolstering food- and climate security, agronomic intervention programs should consider smallholders’ limited monetary incentives to invest in intensification. Irrigation-led agricultural intensification programs and policies should explicitly account for the heterogeneity in household resources, irrigation levels, and degree of dependence on agricultural income.

In Ecuador, farmers poorly adopt practices to manage potato seed degeneration. This could be related to the deficient understanding of the farmers’ capacity to experience seed degeneration and respond to it. We contribute to this understanding by answering: How do farmers experience seed degeneration?; What practices do farmers implement when their seed is degenerated?; and Is experiencing degeneration the pivotal factor determining how farmers replace their seed regardless their income? We analysed data collected in Ecuador through farmers’ focus group discussions, farmers’ surveys and interviews, and the Ecuadorian employment status survey. We found that approximately half of the farmers experienced degeneration. Farmers experienced it through low yields, change in seed appearance, crop weakening, and seed physiological problems. When farmers experienced degeneration, they replaced their seed, sought for technical advice, applied more agricultural inputs, or grew other crops. Income was an important trigger for farmers to change their seed replacement practices.

Root anatomical phenotypes present a promising yet underexploited avenue to deliver major improvements in yield and climate resilience of crops by improving water and nutrient uptake. For instance, the formation of root cortical aerenchyma (RCA) significantly increases soil exploration and resource capture by reducing the metabolic costs of root tissue. A key bottleneck in studying such phenotypes has been the lack of robust high-throughput anatomical phenotyping platforms. We exploited a phenotyping approach based on laser ablation tomography, termed Anatomics , to quantify variation in RCA formation of 436 diverse maize lines in the field. Results revealed a significant and heritable variation for RCA formation. Genome-wide association studies identified a single-nucleotide polymorphism mapping to a root cortex-expressed gene-encoding transcription factor bHLH121. Functional studies identified that the bHLH121 Mu transposon mutant line and CRISPR/Cas9 loss-of-function mutant line showed reduced RCA formation, whereas an overexpression line exhibited significantly greater RCA formation when compared to the wild-type line. Characterization of these lines under suboptimal water and nitrogen availability in multiple soil environments revealed that bHLH121 is required for RCA formation developmentally as well as under studied abiotic stress. Overall functional validation of the bHLH121 gene’s importance in RCA formation provides a functional marker to select varieties with improved soil exploration and thus yield under suboptimal conditions.

CONTEXT: Wheat-maize (W-M) double cropping is the dominant land use system in the North China Plain (NCP). This system has high grain output but suffers from high fertilizer input and nitrogen (N) surplus. Meanwhile, the market demands more protein and oil crops, such as soybean or peanut. OBJECTIVE: Here, we assess whether incorporation of legumes into W-M via intercropping with maize can contribute to lower annual N input while maintaining high annual outputs and diversifying products with high yield stability. METHODS: We compared yield, yield stability, and profitability of six rotation systems: W-M30 (at the maize inter-plant distance of 30 cm), the density-increased W-M20, wheat-soybean (W-S), wheat-peanut (W-P), and wheat with an intercrop of maize (at the inter-plant distance of 20 cm) and soybean (W-MS) or peanut (W-MP). Four annual N input levels were compared: N0 (no N input), N1 (reduced N input), N2 (target practice), and N3 (current high input). RESULTS AND CONCLUSIONS: Results over four years showed that replacing maize by maize/legume intercrops had a similar wheat yield as that of W-M while the N input was intermediate between W-M and W-legume rotations. Total actual/equivalent grain yields and gross margins of W-MS or W-MP were consistently intermediate between W-M and W-legume rotations. Intercropping enhanced the yield and temporal yield stability of maize per plant, with benefits for both yield stability of the intercropping system of maize season and the annual rotation system. Averaged over six rotation systems, increasing N supply increased the annual total actual/equivalent grain yield, gross margin and yield stability to a plateau starting at N1 or N2, without a further significant increase at N3. Specifically, the response of total equivalent yield or gross margin of each annual system to increasing N supply could be fitted by the linear-plateau model. Compared to the response curve of W-M, W-MS and W-S reached the plateau with a lower N input and higher yield and profit, while W-MP and W-P reached the plateau with lower N input but decreased the yield and profit. Compared to W-M with 240–360 kg N/ha/year, W-MS used 210–320 kg N/ha/year saving 11.1–12.5% fertilizer N, while maintaining or improving production by 9.1–13.0%, and improving profitability by 12.1–15.6% and temporal yield stability by 12.8–50.6%. SIGNIFICANCE: W-MS diversifies products with lower N input and higher outputs, profitability, and temporal yield stability than conventional W-M, thus is highly recommended towards productive and sustainable agriculture in the NCP.

This study aimed to understand the morphophysiological responses and primary metabolism of tomato seedlings subjected to mild levels of nitrogen and/or water deficit (50% N and/or 50% W). After 16 days of exposure, plants grown under the combined deficit showed similar behavior to the one found upon exposure to single N deficit. Both N deficit treatments resulted in a significantly lower dry weight, leaf area, chlorophyll content, and N accumulation but in a higher N use efficiency when compared to control (CTR) plants. Moreover, concerning plant metabolism, at the shoot level, these two treatments also responded in a similar way, inducing higher C/N ratio, nitrate reductase (NR) and glutamine synthetase (GS) activity, expression of RuBisCO encoding genes as well as a downregulation of GS2.1 and GS2.2 transcripts. Interestingly, plant metabolic responses at the root level did not follow the same pattern, with plants under combined deficit behaving similarly to W deficit plants, resulting in enhanced nitrate and proline concentrations, NR activity, and an upregulation of GS1 and NR genes than in CTR plants. Overall, our data suggest that the N remobilization and osmoregulation strategies play a relevant role in plant acclimation to these abiotic stresses and highlight the complexity of plant responses under a combined N+W deficit.

Managing outbreaks of alien plant pests is key to preserving biodiversity and safeguarding crop production. Zoning strategies are applied by plant health authorities to tailor measures to the risk of spread in relation to distance from the outbreak epicentre and the biology of the pest. Here we synthesize information on outbreak management to evaluate the diversity and consistency of such approaches. We collected information on the zoning strategies of 121 outbreaks of 25 plant pests in the European Union (EU). According to the organism’s presence and the measures applied, five zones were distinguished: an infested zone (83% of cases), a buffer zone (76%), a clear-cutting zone (28%), an eradication zone (1%) and a containment zone (1%). Infested zones and buffer zones were adjacent non-overlapping zones, while the clear-cutting zone, eradication zone or containment zone was within either the infested zone or buffer zone. A combination of infested and buffer zones was used in 51% of recorded cases. Measures differed within different zones. Destruction of infested plants in the infested zone was done in 78% of the cases, while surveillance was always applied in the buffer zone. Regulation of an organism at EU level led to a convergence of zoning strategies applied by different member states. Regulations often prescribed the greatest widths used before regulations were issued. Further analyses are needed to explore the efficacy of different strategies including the costs of each strategy. Such analyses should combine insight from practice with bio-economic modelling.

Grazing exclusion changes soil physical-chemical characteristics, rapidly affects microbial community composition and function, and alters biogeochemical processes, e.g., carbon (C) cycle, over time. However, the temporal dynamics of CO2 emission and CH4 uptake during grassland restoration chronosequences remain poorly understood. We investigated soil CO2 emission and CH4 uptake, the genes related to CO2 and CH4 production and reduction (cbbL, cbbM, chiA, and pmoA), and associated microbial communities under different durations of grazing exclusion (0, 7, 16, 25, and 38 years) to reveal the mechanisms and potential of soil CO2 emission and CH4 uptake in a semi-arid steppe. The results showed that a proper exclusion period could significantly improve soil physical-chemical conditions, vegetation community, and soil C-cycling. The abundance of C-cycling functional genes (cbbL, cbbM, chiA and pmoA), CH4 uptake and CO2 emission rates showed a single-peak pattern with increasing duration of grazing exclusion, peaking at 16 years and then decreasing in the period between 25 and 38 years, indicating that the effect of exclusion weakened when the exclusion period was too long. The changes in C-cycling functional genes and microbial communities are primarily influenced by aboveground net primary productivity (ANPP), and are associated with CO2, CH4, soil water content (SWC), and soil organic carbon (SOC). Structural equation modeling showed that increases in SOC content and pmoA abundance caused by an increase in ANPP accelerated CO2 emission and CH4 uptake rates, respectively. Our results provide valuable insights into the critical role of grazing exclusion in promoting grassland restoration and carbon sequestration, and have potential implications for sustainable land management practices.

Intercropping, also known as mixed cropping, consists on simultaneously growingmore than one species on a field. It has a great potential for enhancing water- and nutrientuseefficiency and improving plant productivity, yield stability and resilience to biotic and abiotic stress, including those triggered by climate change. Despite their manifold benefits,the practice of intercropping has not risen above its niche status in many regions of theworld. The selection of varieties specifically adapted to intercropping remains a major practical challenge to its widespread deployment. This Editorial of a Research Topic hosted at Frontiersin Plant Sciences entitled “Breeding for intercropping” gathers a series of articles coveringnew insights in the areas of quantitative genetics, ecology, ecophysiology and agronomyintegrating theoretical, experimental as well as participatory approaches.

To identify if and how the age of in vitro potato plantlets at planting affects the later tuber formation, an extensive pot experiment was performed under controlled conditions. In vitro-derived plantlets of different ages (14, 28, 42 and 56 days old at planting) and cultivars varying in maturity type (Gloria, very early; Bintje, mid-early; Elkana, late) were grown after planting for 10 weeks at photo/thermoperiods of 16 h (standard conditions) or 12 h (short-day conditions). Plants raised from older in vitro plantlets produced higher total dry weights, harvest index and tuber dry and fresh weights than plants from younger in vitro plantlets when grown under standard conditions after planting. By contrast, total and tuber dry weights were not affected by plantlet age when grown under short-day conditions. The number of tubers per plant increased with increase in in vitro plantlet age in the later cultivars and in the oldest age classes of the very early cultivar when plants were grown under standard conditions. Short-day conditions resulted in fewer, but larger tubers than standard conditions. Results support the ideas that (1) plants from older in vitro plantlets and earlier maturing cultivars are more advanced in the tuber formation process; however, this may benefit tuber yield only when plants are grown under conditions that are not strongly inducing tuberization, and (2) higher tuber numbers can be achieved by more below-ground nodes—as in older in vitro plantlets—and/or by later or less strong tuber induction—as in less inducing conditions (16-h vs. 12-h), later cultivars or younger in vitro plantlets.

Context or problem: The reallocation of dry matter (DM) and nitrogen (N) from vegetative tissues to the grains are critical for both yield quantity and protein content of cereal crops. However, it is unclear to which extent the dynamics in DM and N reallocation depend on N availability, and how individual leaves within the maize canopy respond to different N availabilities in terms of these processes. Objective or research question: This study aimed to quantify DM and N accumulation, partitioning, and reallocation from vegetative to reproductive parts in maize in relation to soil N availability. Methods: A long-term N fertilizer trial was conducted in Jilin province, Northeast China, growing maize at three N fertilizer levels (low N availability, N0; intermediate N availability, N1; and high N availability, N2). The accumulation, partitioning, and reallocation of DM and N were quantified at the whole-plant, organs, and single-leaf scales in 2015 and 2016. Results: Although both post-silking DM accumulation and post-silking N uptake increased in response to higher N availability, 8.3–38.8% of grain N still needed to be reallocated from vegetative organs with a larger fraction coming from leaves (10.5 – 36.5%) than from stems (4.4 – 11.6%). This dependency of grain N on N reallocation from vegetative parts increased at lower soil N availability. Furthermore, the vertical patterns of reallocated leaf DM and reallocated leaf N changed with N availabilities. While in general leaves in the middle part of the canopy tended to reallocate more DM and N to the grains than leaves from the upper or lower canopy parts, these most-contributing leaves were higher in the canopy at low than at high N availability. Conclusions and implications: Grain N relies on reallocation more than does grain DM. At lower N availability, more grain DM and grain N need to be reallocated from vegetative organs. Furthermore, the leaf ranks from which most DM and N were reallocated, gradually increased from the bottom to upper ranks as N availability decreased. Together, our results on the dynamics of N and DM uptake and reallocation during the reproductive phase are important for plant and crop models that require these processes for accurate predictions of maize performance.

Improving the quality of seed potatoes that smallholder farmers plant continues to represent one of the most important challenges of the potato sector in most developing countries to counter the long-lasting poor yields. This study aimed to better understand the way farmers choose seed potato by exploring the attributes they look for and the benefits they expect from them. We used means-end chains analysis in combination with Kelly’s repertory grid as an elicitation technique and disaggregated data for male and female partners. In total, farmers named 38 attributes they look for when selecting seeds. Farmers associate “good” seeds to those that are well-sprouted, have many eyes, are of a variety they know, are medium in size, are certified, and are undamaged. Most preferred attributes lead to a higher yield and consequently higher income which is the most predominant avenue for farmers to achieve their desired values in life. Female farmers mentioned fewer attributes and also pursued fewer values than their male counterparts. Users and non-users of certified seed were shown to use the same attributes to select their potato seeds. Non-users of certified seed thus seem to be aware of the benefits of certified seed even though they are not using it. The results from this study indicate that increasing the availability of certified seed is not necessarily a straightforward way of improving the quality of seed potato planted by Kenyan smallholder farmers.

Cocoa is an important commodity crop and source of income for millions of small-holder farmers. Nonetheless, questions on cocoa tree functioning, best management practices and climate change responses remain. Modelling is a powerful tool to address these questions, complementing experimental work that is expensive and time consuming due to the long productive cycle of the cocoa system. However, compared to other crops, cocoa modelling has not received as much attention. OBJECTIVE: We reviewed existing cocoa models and identified the main gaps in the literature and possible strategies to advance models of cocoa production. METHODS: We first classified relevant research questions in cocoa production along three main axes (fundamental-applied, spatial organization, prediction horizon) and aligned modelling approaches along these. We then reviewed six published cocoa models using these axes as framework. This comparison revealed several modelling gaps for which we provide an overview of data availability for future model development. RESULTS: (i) Several plant processes (i.e., water stress responses, respiration, climate change responses, nutrient effects and phenology) are either missing from existing cocoa models or are simulated based on general plant physiological knowledge rather than cocoa-specific knowledge. (ii) The only currently existing 3D model of cocoa architecture has very limited scope and does not include physiological processes. (iii) There are no model-based decision support tools available for supporting the main management practices such as irrigation, fertilization and pruning. (iv) Data for model calibration and validation are often scarce. CONCLUSIONS: We conclude that data availability for model design, calibration and validation is currently the main bottleneck for further development of cocoa models. Extensive cooperation within the cocoa research community and a large network of long-term experiments under different climatic and management conditions are required to close the identified modelling gaps.

CONTEXT: To avoid excessive chemical-fertilizer application and improve agricultural productivity in rice, a fertilizer recommendation system called Nutrient Expert® (NE) was designed. However, the ability of NE to balance yield, profitability and environmental sustainability in rice production needs to be further evaluated, as it is still difficult for farmers to assess the proper nitrogen (N) application rate. OBJECTIVE: The objective of this study was to demonstrate the advantages of the NE system in balancing yield, profitability and N loss in rice production, and recommend proper N application rates for different cropping seasons of rice. METHODS: This study describes results from field experiments conducted in five main rice cropping provinces from 2017 to 2020 in China, to investigate any advantages of NE compared with local farmers' practice (FP), and to determine the proper N application rates for different cropping seasons of rice. RESULTS AND CONCLUSIONS: Compared with FP, NE had 12.1% lower N-fertilizer application, but increased rice grain yield by 4.3% and net profit by 7.4%, and decreased yield-scaled N loss by 20.7%. We showed how yield, profitability and N loss were affected by N balance (i.e., N applied to the field minus N removed from the field by the harvested crop biomass), and quantified relationships between N balance and N application rate, and between N output and input. Based on relationships between N balance and N application rate, we recommend N application rates in a range from 122 to 214 kg ha−1, depending on cropping seasons of rice. We demonstrated that NE can simultaneously improve yield, profitability and environmental sustainability. SIGNIFICANCE: Our study provided quantitative support for NE-based recommendations on the N application rate for smallholders farming in different rice cropping systems, and these recommendations can serve as a reference for avoiding excessive N application rate in paddy fields in other regions with similar eco-environment.

Combinability of species in intercrops depends on the production conditions and there is limited information on the potential of intercropping under conventional (i.e., non-organic) management in Western Europe. Here we determined productivity of four crop species (maize, Zea mays L.; wheat, Triticum aestivum L.; faba bean, Vicia faba L.; pea, Pisum sativum L.) in six different bi-specific mixture compositions. Species were spring-sown and fertilized in their strips according to common practice for monocrops. Strips were 1.5 m wide enabling strong interspecific interactions. Intercrops with maize, a species sown and harvested later than the other three species, had land equivalent ratio (LER) values that were in four out of six cases significantly greater than one, from 1.14 ± 0.04 to 1.22 ± 0.05 in 2018, and from 0.98 ± 0.06 to 1.15 ± 0.01 in 2019. Simultaneous intercrops comprising two of the other three species had LER values that tended to be lower than one, even though many LERs were not significantly different from one: from 0.94 ± 0.02 to 0.95 ± 0.04 in 2018, and from 0.80 ± 0.08 to 0.93 ± 0.04 in 2019. The yield gain (net intercropping effect; NE) in relay intercrops with maize ranged from 1.33 ± 0.59 to 2.01 ± 0.54 Mg ha−1 in 2018, and from 0.29 ± 0.41 to 1.04 ± 0.14 Mg ha−1 in 2019. The NE of simultaneous intercrops ranged from −0.43 ± 0.13 to −0.27 ± 0.22 Mg ha−1 in 2018, and from −1.17 ± 0.49 to −0.36 ± 0.22 Mg ha−1 in 2019. Results indicate that temporal complementarity between species drove the LER (or NE) in these experiments. On the other hand, values of the LER (or NE) were similar in species combinations with or without legumes, suggesting no major role for complementarity for nitrogen capture under the conditions of the study. Faba bean was the most competitive species and reached high partial LER and NE values in intercrops at the expense of the companion species. Competition from faba bean reduced the grain yield of wheat and pea more than it increased faba bean grain yield, resulting in negative net effects. Results suggest that relay strip intercropping can improve land use efficiency and total grain yield in conventional farming in Western Europe if species have temporal complementarity.

Preceding crop and nitrogen (N) fertilization affect N cycling and productivity of subsequent wheat in double cropping. However, the effects of preceding crop and N fertilization on relationships between yield and “mineral nutriome” or nutritional quality (amount and bioavailability) in wheat grains have not been well characterized, particularly not in the case of multiple mineral nutrient elements and when considering cumulative effects of fertilization strategies in long-term field experiments. Here we present effects of preceding crop (monocultures of maize, peanut or soybean, and intercropping of maize with peanut or soybean) at 4 levels of annual fertilizer N input (0–440 kg/ha) on yield traits, major mineral nutrients and their relationships in wheat grains in a 4-years continuous double-cropping field experiment in the North China Plain. Nitrogen fertilizer increased wheat grain yields, mass concentrations of N and copper (Cu), and micronutrient (mainly zinc: Zn and iron: Fe) bioavailability, while no N supply was associated with low grain yield, N and Cu concentrations and micronutrient bioavailability, high mass concentrations of Zn, manganese, phosphorus (P), calcium, magnesium and phytate-P, and a high ratio of phytate-P/P. Moderately lowering N input from the in-season 240 to 200 kg/ha (but not 120 kg/ha) would not harm grain yield and most nutritional traits. Compared to significant effects of N application level on almost all grain yield and nutritional traits, and soil properties, preceding crops had less impact and only grain yields and Zn concentrations were significantly affected. Grain yields, N and Zn concentrations varied dramatically from an average of 2.7 to 7.6 t/ha, 16.5–19.3 g/kg and 15.1–19.8 mg/kg with different N application levels, respectively; while varied relatively little from 5.9 to 6.6 t/ha, 17.8–18.3 g/kg and 16.1–18.1 mg/kg under different preceding crops, respectively. Compared to the conventional wheat-maize rotation, a legume pre-crop monoculture but not maize/legume intercropping increased grain yields by 5.0–11.9% on average, but reduced grain Zn concentrations from 17.5–17.8 to 16.1 mg/kg significantly. The legume effect was most significant at zero or low N supply. The relationship between grain yields and Zn concentrations was adequately described by a concave-up parabola (R2 = 0.3001, P < 0.0001, n = 288), suggesting appropriate N fertilization and rotation can achieve high-yield while ameliorating the dilution of grain Zn density. Therefore, our findings provide new insight in relationships among agronomic practices, wheat grain yield and grain nutritional quality (particularly for Zn).

Abstract Field trials to evaluate the performance of new varieties are an essential component of potato breeding. Besides the genetic differences, environmental factors can lead to variation in a trial. In variety trials, the observed differences amongst varieties should reflect genetic differences, without a large impact of the random or systematic variation in the field. One way to reduce within-field variation is to adjust the plot size and its shape in a trial. Two years of field trials in which individual plants in 90-plant plots of both diploid hybrid and tetraploid varieties were measured provided data to derive relationships between LSD% and plot size and shape. We provide a method to estimate the equations to calculate the expected variation when using different plot dimensions in a relatively homogeneous trial field for tuber yield, tuber volume, tuber count, tuber shape and the standard deviations of tuber volume and shape. Compared with the yield traits, the variation for tuber shape was relatively small. The effect of plot shape was minor. With these equations, breeders can determine what plot dimensions are needed to reach the desired precision for each trait.

To contribute to the development of a novel cropping system for potato grown from greenhouse-derived seedlings from hybrid true potato seeds, planting density trials were carried out under normal Dutch agronomic conditions. For two consecutive years, 5-week-old seedlings of two experimental genotypes were transplanted into farmers’ potato production fields at two contrasting locations: a flat-bed system on sandy soil and a traditional ridge system on clay soil. Planting densities were 6.25, 12.5, 25, 50, 100 and 200 plants/m2 in the flat-bed system, and 3.125, 4.688, 6.25, 12.5, 25 and 50 plants/m2 in the ridge system. In general, increasing planting density of hybrid seedlings per area decreased tuber fresh weight per plant and reduced the number of tubers per plant. On a per hectare basis, an increased planting density resulted in increased total tuber yield and number of tubers up to very high densities, but finally both parameters levelled off. Highest total tuber yields harvested were 107 and 45 Mg/ha for the flat-bed and ridge system, respectively. On flat-beds, the optimal planting density for total yield was 50 plants/m2. On ridges, planting density interacted with year and genotype, resulting in an optimum planting density of 25 plants/m2 to reach the maximum total yield. Obtained yields in the commercial size classes Baby Baker (20 2. The current study showed that transplanted hybrid seedlings are feasible alternatives for seed-tuber-grown systems for certain potato outlets.

Nitrogen (N) utilization for crop production under N deficiency conditions is subject to a trade-off between maintaining specific leaf N content (SLN) important for radiation-use efficiency versus maintaining leaf area (LA) development, important for light capture. This paper aims to explore how maize deals with this trade-off through responses in SLN, LA and their underlying traits during the vegetative and reproductive growth stages. In a 10-year N fertilization trial in Jilin province, Northeast China, three N fertilizer levels have been maintained: N deficiency (N0), low N supply (N1) and high N supply (N2). We analysed data from years 8 and 10 of this experiment for two common hybrids. Under N deficiency, maize plants maintained LA and decreased SLN during vegetative stages, while both LA and SLN decreased comparably during reproductive stages. Canopy SLA (specific leaf area, cm2 g–1) decreased sharply during vegetative stages and slightly during reproductive stages, mainly because senesced leaves in the lower canopy had a higher SLA. In the vegetative stage, maize maintained LA at low N by maintaining leaf biomass (albeit hence having N content/mass) and slightly increasing SLA. These responses to N deficiency were stronger in maize hybrid XY335 than in ZD958. We conclude that the main strategy of maize to cope with low N is to maintain LA, mainly by increasing SLA throughout the plant but only during the vegetative growth phase.

Viruses pose a major challenge to sweetpotato production in Tanzania. Use of cleaned-up, virus-tested seed vines distributed through a formal seed system is among the proposed strategies to address this challenge. However, virus-tested seed vines can get infected once in the field and it is not known how they will perform following several seasons of on farm propagation. We assessed the performance of virus-tested seed vines and farmer-sourced seed vines of a susceptible variety, Ejumula, and a relatively tolerant variety, Kabode, over five seasons to understand the trend in root yields, vine yields and virus incidences. The experiments were done in high and low virus pressure areas. The most prevalent viruses were sweet potato chlorotic stunt virus (SPCSV) followed by sweet potato feathery mottle virus (SPFMV) and sweet potato leaf curl virus (SPLCV), respectively. Both farmer-sourced and cleaned-up, virus-tested seed of cv. Ejumula were rapidly infected with SPCSV. The incidence of this virus on Ejumula's farmer-sourced material at the high-virus-pressure area reached 100% by the second season. The incidences for all three viruses remained stable for cv. Kabode across the five seasons. Plants generated from cleaned-up, virus-tested seed had lower incidences for all viruses compared to those from farmer-sourced planting material. Virus-tested seed produced significantly higher root yields for cv. Ejumula in the high-virus-pressure site, with a gradual drop across the seasons. The findings show that regular replenishment of clean, virus-tested seed is more economical in high-virus-pressure areas and for more susceptible varieties like cv. Ejumula. They also indicate that farmers may be reluctant to invest in cleaned-up, virus-tested seed in cases where they have virus-tolerant varieties such as cv. Kabode due to lack of obvious virus effect on yields.

Maize-legume intercropping is common in sub-Saharan Africa. Effects of legumes on the companion maize crop are determined principally by choice of legume species and relative introduction time. Performance of intercrops is optimized when legumes' planting is timed such that their peak growth phase occurs after maize harvest, with legumes utilizing the residual soil moisture. OBJECTIVE: We sought to understand the role of inter-specific competition for water in maize-pigeonpea and maize-lablab intercrops. METHODS: We analysed experimentally determined shoot biomass of sole and intercropped maize, lablab, long and medium- duration pigeonpea. Experiments were conducted in northern Tanzania for two consecutive seasons. The second season was drier (236 mm) than the first (551 mm). We constructed a parameter-sparse growth model, calibrated based on sole crops data. The model calculates growth rate as radiation interception × radiation-use efficiency. When simulated actual soil moisture content fell below a species-specific critical level, the ratio between actual and potential transpiration for that species decreased, and crop growth rate was reduced proportional to this reduction. RESULTS AND CONCLUSIONS: There was good agreement between simulated and observed shoot biomass of maize and the legumes. With rooting depth of 60 cm, maize was simulated to be sensitive to annual precipitation, resulting in 3.5 t ha−1 (34%) reduction in shoot dry matter production in the second season. By contrast, the legumes, with a rooting depth of 200 cm did not experience water shortage in either of the two seasons, resulting in nearly identical shoot dry matter production in both seasons. Explorative simulations assuming the legumes to have shallower rooting depth confirmed the importance of this trait for avoidance of water stress, with simulated reductions in dry matter production of 23–34% for the legumes when rooting depth was reduced from 200 to 60 cm. Maize in the intercrop was modestly influenced by the legumes due to light competition. In the low precipitation season, additional competition for water occurred and water shortage for maize was aggravated. Maize influenced the legumes only through competition for light, as a tap root allowed the legumes to utilize water stored in deeper soil layers. During the co-growth period, competition for light exerted by maize on the legumes was strong, but they partly compensated for this in the period after maize harvest. SIGNIFICANCE: Our results emphasize the important role of the deep legume tap root for the success of maize-legume intercrops under rain-fed conditions.

A novel cropping system for potato was tested for two consecutive years under normal Dutch agronomic conditions. Seedlings from two experimental genotypes of hybrid true potato seeds were produced in a greenhouse nursery and transplanted into the field 5 weeks after sowing to assess tuber yield levels and to study effects of hilling on tuber yield and number, tuber size distribution and tuber greening. Field experiments had a split-plot design with hilling treatments as the main plots and genotypes as the sub-plots. Final harvest was at 122 and 132 days after transplanting in 2017 and 2018, respectively. Hybrid seedlings were transplanted into small initial ridges and irrigated straight after planting. Three hilling treatments were applied between transplanting and 100% canopy cover. Treatment ‘zero hilling’ did not receive any additional hilling after transplanting. Treatments ‘double hilling’ and ‘triple hilling’ received two and three additional hilling treatments, respectively. Total tuber yields at final harvest in both years were not affected by the hilling treatments. Yields for the respective genotypes were 26 and 30 Mg/ha in 2017 and 25 and 32 Mg/ha in 2018. Total tuber numbers were only affected by hilling treatments in 2017, where under hilled conditions, plants produced more tubers compared with plants under zero hilling. Plants under zero hilling yielded more tubers in size class > 40 mm compared with triple hilling in 2017. In 2018, no significant effects of hilling on tuber numbers were found, but the trend was similar to that in 2017.

Aim Recycling of cocoa pod husks has potential to contribute to mineral nutrition of cocoa. Yet little is known of the nutrient content and nutrient release patterns from the husks. The potassium (K) rich husks are usually left in heaps in cocoa plantations in Africa. We aimed to understand and quantify release patterns of K and other nutrients from husks under varying rainfall regimes and assessed the effects of partial decomposition and inundation on nutrient leaching rates. Methods We incubated chunks of cocoa pod husks to assess decomposition rates and we measured nutrient leaching rates from two sets of husk chunks: one set was placed in tubes that were submitted to simulated scheduled rainfall events while the second set was continuously inundated in beakers. Results Decomposition of husks followed a second-order exponential curve (k: 0.09 day−1; ageing constant: 0.43). Nutrient losses recorded within 25 days were larger and more variable for K (33%) than for other macronutrients released in this order: Mg > Ca ≈ P > N (less than 15%). Potassium leaching was mainly driven by rainfall frequency (P Conclusion Some initial decomposition of cocoa pod husks is required to expose K to intense leaching. As decomposition progresses, abundant K losses are to be expected under frequent and/or intense rainfall events.

Deinococcus radiodurans, an important extremophile, possesses extraordinary stress tolerance ability against lethal and mutagenic effects of DNA-damaging agents, such as γ-rays, ultraviolet, oxidation, and desiccation. How global regulators of this bacterium function in response to oxidation and desiccation has been an intense topic as elucidating such mechanisms may help to facilitate some beneficial applications in agriculture or medicine. Particularly, a variety of functional proteins have been characterized for D. radiodurans’ behaviors under abiotic stresses. Interestingly, a group of Late Embryogenesis Abundant proteins (LEAs) in D. radiodurans have been characterized both biochemically and physiologically, which are shown indispensable for stabilizing crucial metabolic enzymes in a chaperone-like manner and thereby maintaining the metal ion homeostasis under oxidation and desiccation. The rapid progress in understanding deinococcal LEA proteins has substantially extended their functions in both plants and animals. Herein, we discuss the latest studies of radiodurans LEA proteins ranging from the classification to structures to functions. Importantly, the harnessing of these proteins may have unlimited potential for biotechnology, engineering and disease treatments.

Weeds are a major threat to crop production in agriculture. If left uncontrolled, weeds have a potentially large adverse effect on crop production through competition with crops for limiting light, water, and nutrients. Intercropping, as a spatial diversification measure, has shown potential for ecological weed management in many cases. This thesis aimed to investigate the extent to which weed suppression can be achieved by annual intercrops consisting of two main crop species and to explore the possible underlying mechanisms for weed suppression.A global meta-analysis showed that intercropping is generally a useful approach for species with poor weed suppressiveness to improve weed management. On average, weed biomass in intercrops was substantially (58%) lower than that in weaker weed-suppressive sole crops, and it was similar to that in stronger weed-suppressive sole crops. This pattern emerged across species combinations such as maize/legume and small-grain cereal/legume intercrops. An additive design gave stronger weed suppression than a replacement design, showing the important role of plant density on weed suppressiveness. Spatial arrangement mattered in replacement systems: a mixed pattern gave stronger weed suppression than a row pattern. Weed suppressiveness of intercrops was not affected by being either simultaneous or relay systems, and it was not affected by the level of nitrogen fertilizer input. Three models (i.e., arithmetic mean, weighted arithmetic mean, and weighted harmonic mean) were developed to predict weed biomass in intercrops. The model valuation was used to explore the relevance of possible mechanisms (i.e., complementarity, selection, and plant density) underlying weed suppression in intercrops. The arithmetic mean and weighted arithmetic mean resulted in a systematic overestimation of the weed biomass in intercrops. The weighted harmonic mean was able to provide a good prediction of the observed weed biomass in intercrops. This model reflects how much weed biomass to expect based on the relative densities of the species in a mixture and species-specific weed suppression in pure stands, therefore the model does not account for the contribution of complementarity between intercropped species to weed suppression. The good prediction suggests that except plant density effect, selection of the stronger weed-suppressive species is an important mechanism while complementarity is of less importance for weed suppression. For intercropping with a less intimate intermingling of the two component species, either due to temporal (relay intercrops) or spatial (strip intercrops) separation, the harmonic mean tended to underestimate observed weed biomass. In the subsequent meta-analysis, findings based on crop yield or biomass data supported the important role of the selection effect on weed suppression in intercrops. The net effect ratio (NER) of the strongly weed suppressive species was 1.33 times as large as the NER of the weaker weed suppressive species, showing the occurrence of species competitive dominance. A better weed-suppressive ability of a species in the pure stand was associated with a better competitive position in intercrop. Species dominance was stronger in intercrops with a mixed configuration than in intercrops with a row or strip arrangement. Species dominance occurred in small-grain cereal/legume intercrops but not in maize/legume systems. Differences in species’ weed-suppressive abilities resulted in stronger species dominance in additive designs than in replacement designs. In addition to the analysis of literature data, I conducted a preliminary analysis using functional structural plant (FSP) modelling. Simulations from FSP modelling revealed that a selection effect of species with stronger weed suppressiveness occurs particularly during early growth, resulting in weed suppression in intercrops that is better than the average of sole cropsOverall, this thesis showed that intercropping is a promising strategy for crop species with poor weed suppressiveness to increase “within-season” weed suppression. Findings confirm the important role of plant density in weed suppression. In intercrops with close interaction between species, a selection effect steered by species with stronger weed suppressiveness is an important mechanism underlying weed suppression. In such cases, the weighted harmonic mean model provides a good prediction of the weed biomass. Future research should focus on the competitive balance between intercropped species and between crop and weed species in order to obtain a satisfying yield and weed suppression in intercrops.

Funder: Agua Salud Project, Funder: U.S. Department of Energy; Id: http://dx.doi.org/10.13039/100000015, Funder: CAPES; Id: http://dx.doi.org/10.13039/501100002322, Data capturing multiple axes of tree size and shape, such as a tree's stem diameter, height and crown size, underpin a wide range of ecological research-from developing and testing theory on forest structure and dynamics, to estimating forest carbon stocks and their uncertainties, and integrating remote sensing imagery into forest monitoring programmes. However, these data can be surprisingly hard to come by, particularly for certain regions of the world and for specific taxonomic groups, posing a real barrier to progress in these fields. To overcome this challenge, we developed the Tallo database, a collection of 498,838 georeferenced and taxonomically standardized records of individual trees for which stem diameter, height and/or crown radius have been measured. These data were collected at 61,856 globally distributed sites, spanning all major forested and non-forested biomes. The majority of trees in the database are identified to species (88%), and collectively Tallo includes data for 5163 species distributed across 1453 genera and 187 plant families. The database is publicly archived under a CC-BY 4.0 licence and can be access from: https://doi.org/10.5281/zenodo.6637599. To demonstrate its value, here we present three case studies that highlight how the Tallo database can be used to address a range of theoretical and applied questions in ecology-from testing the predictions of metabolic scaling theory, to exploring the limits of tree allometric plasticity along environmental gradients and modelling global variation in maximum attainable tree height. In doing so, we provide a key resource for field ecologists, remote sensing researchers and the modelling community working together to better understand the role that trees play in regulating the terrestrial carbon cycle.

Plant breeding for increased crop water use efficiency or drought stress resistance requires methods to quickly assess the transpiration rate (E) and stomatal conductance (gs) of a large number of individual plants. Several methods to measure E and gs exist, each of which has its own drawbacks and shortcomings. To add to this toolbox, we developed a method that uses whole-plant thermal imaging in a controlled environment, where aerial humidity is changed rapidly to induce changes in E that are reflected in changes in leaf temperature. This approach is based on a simplified energy balance equation, without the need for a reference material or complicated calculations. To test this concept, we built a double-sided, perforated, open-top plexiglass chamber that was supplied with air at a high flow rate (35 L min− 1) and whose relative humidity (RH) could be switched rapidly. Measurements included air and leaf temperature as well as RH. Using several well-watered and drought stressed genotypes of Arabidopsis thaliana that were exposed to multiple cycles in RH (30 to 50% and back), we showed that leaf temperature as measured in our system correlated well with E and gs measured in a commercial gas exchange system. Our results demonstrate that, at least within a given species, the differences in leaf temperature under several RH can be used as a proxy for E and gs. Given that this method is fairly quick, noninvasive and remote, we envision that it could be upscaled for work within rapid plant phenotyping systems.

The recent invention of hybrid breeding technology for potato has led to an increased interest in hybrid potato R&D. Hybrid true potato seeds (TPS) are used to produce planting materials such as transplants and seedling tubers, but can also be used for direct seeding of seed or ware crops. Transplants and seedling tubers can be used to produce seed tubers or ware tubers. The rise in R&D in hybrid breeding creates the need for phenological scales of growth and development of plants produced by the various planting material types of hybrid-TPS. The BBCH (Biologische Bundesanstalt, Bundessortenamt and CHemical Industry) scale is one of the phenological scales developed for the description of the growth and development stages of plants. In 1993, a BBCH scale with descriptions for potato plants was released. The original BBCH scale gave standardised descriptions for TPS- and tuber-grown plants. Differences in the morphology of plants originating from the different planting materials in terms of types of branches and differences in below-ground growth and development were not included. Moreover, for reproductive growth stages, crucial for hybrid breeding, the original scale is incomplete as it does not carefully take the complex sympodial branching into account. Methods of describing growth of tubers and berries are complex and impossible to use when final tuber mass or berry size is unknown. The current paper augments the original BBCH scale, while retaining its structure and logic. It provides alternative and comprehensive descriptions of growth stages suitable for potato plants grown from different types of planting materials, and for all end uses of these plants. The proposed scale is detailed enough for research and breeding but still general enough for agricultural use.

Rice yield reduction due to water limitation depends on its severity and duration and on the phenological stage of its occurrence. We exposed three contrasting rice genotypes, IR64, UPLRi7 and Apo (adapted to lowland, upland and aerobic conditions, respectively), to three water regimes (puddle, 100% and 60% field capacity) in pots during the vegetative (GSI), flowering (GSII) and grain filling (GSIII) stages. Stress at all the three stages significantly reduced yield especially in lowland genotype IR64. Effect of water limitation was more severe at GSII than at the other two stages. Stress at GSI stage reduced both source activity (leaf area and photosynthetic rate) and sink capacity (tiller number or panicle number per pot). When stress was imposed at GSII, spikelet fertility was most affected in all the three genotypes. In both GSII and GSIII, although leaf area was constant in all the three water regimes, estimated relative whole-plant photosynthesis was strongly associated with yield reduction. Reduced photosynthesis due to stress at any given stage was found to have direct impact on yield. Compared to the other genotypes, Apo had deeper roots and maintained a better water relation, thus, higher carbon gain and spikelet viability, and ultimately, higher biomass and productivity under water-limited conditions. Therefore, screening for these stage-dependent adaptive mechanisms is crucial in breeding for sustained rice production under water limitation.

Several constraints affect the performances of the farming system in Chencha suggesting the necessity of adjustments in the farm components. Therefore, an exploration was made to simultaneously optimize operating profit, labour and soil organic matter balances. Data from twelve farms and secondary data on improved technologies were used as bases for the exploration. Using the multi-objective model FarmDESIGN, the optimization was conducted for two scenarios for each farm, i.e., optimization based on the currently existing farm components and practices and by introducing new technologies and practices to amend the current farm management options. The results revealed that the farm operating profit, labour balance and organic matter balance were not yet optimized with the current farm configurations of all farms. But there is ample scope to improve and simultaneously optimize both the economic, social and environmental sustainability either through optimization of management within current farm resources, or through using improved technologies. The highest improvement could be made through combined optimization of management within current farm resources and improved technologies. The major important factor that influenced the optimization was the cropping plan, which might be associated with the management practices applied for a particular crop. However, adjusting areas of crops and implementation of some other optimized solutions may be difficult for individual farmers and requires advice through agricultural extension programmes. Therefore, there is a need to improve the awareness of farmers to wisely manage: crop area and associated crop and soil management practices, land use for eucalyptus, straw use and storage of farm yard manure. Moreover, it is important to diversify off-farm income sources, introduce alternative threshing machineries and improve market access for farm products.

Global dimming, a decadal decrease in incident global radiation, is often accompanied with an increase in the diffuse radiation fraction, and, therefore, the impact of global dimming on crop production is hard to predict. A popular approach to quantify this impact is the statistical analysis of historical climate and crop data, or use of dynamic crop simulation modelling approach. Here, we show that statistical analysis of historical data did not provide plausible values for the effect of diffuse radiation versus direct radiation on rice or wheat yield. In contrast, our field experimental study of 3 years demonstrated a fertilization effect of increased diffuse radiation fraction, which partly offset yield losses caused by decreased global radiation, in both crops. The fertilization effect was not attributed to any improved canopy light interception but mainly to the increased radiation use efficiency (RUE). The increased RUE was explained not only by the saturating shape of photosynthetic light response curves but also by plant acclimation to dimming that gradually increased leaf nitrogen concentration. Crop harvest index slightly decreased under dimming, thereby discounting the fertilization effect on crop yields. These results challenge existing modelling paradigms, which assume that the fertilization effect on crop yields is mainly attributed to an improved light interception. Further studies on the physiological mechanism of plant acclimation are required to better quantify the global dimming impact on agroecosystem productivity under future climate change.

Plant traits—the morphological, anatomical, physiological, biochemical and phenological characteristics of plants—determine how plants respond to environmental factors, affect other trophic levels, and influence ecosystem properties and their benefits and detriments to people. Plant trait data thus represent the basis for a vast area of research spanning from evolutionary biology, community and functional ecology, to biodiversity conservation, ecosystem and landscape management, restoration, biogeography and earth system modelling. Since its foundation in 2007, the TRY database of plant traits has grown continuously. It now provides unprecedented data coverage under an open access data policy and is the main plant trait database used by the research community worldwide. Increasingly, the TRY database also supports new frontiers of trait-based plant research, including the identification of data gaps and the subsequent mobilization or measurement of new data. To support this development, in this article we evaluate the extent of the trait data compiled in TRY and analyse emerging patterns of data coverage and representativeness. Best species coverage is achieved for categorical traits—almost complete coverage for ‘plant growth form’. However, most traits relevant for ecology and vegetation modelling are characterized by continuous intraspecific variation and trait–environmental relationships. These traits have to be measured on individual plants in their respective environment. Despite unprecedented data coverage, we observe a humbling lack of completeness and representativeness of these continuous traits in many aspects. We, therefore, conclude that reducing data gaps and biases in the TRY database remains a key challenge and requires a coordinated approach to data mobilization and trait measurements. This can only be achieved in collaboration with other initiatives.

Bans on the use of synthetic herbicides require innovative management approaches to maintain the attractiveness and usability of turfgrass swards. Such measures should include the use of locally adapted cultivars that germinate and establish quickly, resulting in the densest possible stands. Additionally, a number of turfgrasses have been reported to produce allelopathic substances that inhibit common turfgrass weeds. Mowing heights should be set to achieve maximum weed suppression while still providing acceptable quality for desired use. Sustainable turfgrass management programs have led to a reduction in fertilizer inputs; however, without the availability of herbicides, fertilization regimes need to be re-examined. The literature suggests that broadleaf weeds are reduced but never fully controlled when more N is applied; therefore, finding a balance between what is needed and what is environmentally safe and sustainable is critical. Organic herbicides include plant pathogens from the fungus Phoma and strains of the bacterium Pseudomonas fluorescens. Both can be used to control several weeds common to turfgrasses. Acetic acid has also been shown to have herbicidal activity; however, it has limited residual activity, and its efficacy remains questionable on mature weeds. Thermal weed control can be used to sterilize a seedbank or spot treat existing weeds. Future turfgrass breeding programs could focus on understanding and enhancing the allelopathic potential of turfgrasses to outcompete weeds more effectively. Furthermore, more research should be directed at assessing the competitiveness of certain turfgrasses against weeds within the limitations of producing turfgrass areas of acceptable aesthetics and playing quality.

The metabolic-oxidative stress profile of the rice flag leaf during drought stress in the reproductive stage is highly predictive for grain yield loss sensitivity of 292 accessions at harvest time., Crop yield stability requires an attenuation of the reduction of yield losses caused by environmental stresses such as drought. Using a combination of metabolomics and high-throughput colorimetric assays, we analysed central metabolism and oxidative stress status in the flag leaf of 292 indica rice (Oryza sativa) accessions. Plants were grown in the field and were, at the reproductive stage, exposed to either well-watered or drought conditions to identify the metabolic processes associated with drought-induced grain yield loss. Photorespiration, protein degradation, and nitrogen recycling were the main processes involved in the drought-induced leaf metabolic reprogramming. Molecular markers of drought tolerance and sensitivity in terms of grain yield were identified using a multivariate model based on the values of the metabolites and enzyme activities across the population. The model highlights the central role of the ascorbate–glutathione cycle, particularly dehydroascorbate reductase, in minimizing drought-induced grain yield loss. In contrast, malondialdehyde was an accurate biomarker for grain yield loss, suggesting that drought-induced lipid peroxidation is the major constraint under these conditions. These findings highlight new breeding targets for improved rice grain yield stability under drought.