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Fabrication of sodium-ion full cell (SIFC) with optimized anode and cathode material is in the initial phases. The successful fabrication of full cell is depended on effective improvement in electrode materials and performance of sodium-ion half-cells. Cathode material plays crucial role in the performance of full cell. Sodium-ion full cell was fabricated based P2-type Na0.67Ni0.167Co0.167Mn0.67O2 (Na-NCM) material synthesized by sol-gel process and commercially available hard carbon. The electrochemical properties of Na-NCM material and hard carbon were systematically investigated. The hard carbon material achieved a reversible capacity of 210.82 mAh g−1 with initial columbic efficiency of 81.15% in Na/Hard Carbon half-cell. The Na-NCM material exhibits a discharge capacity of 149.27 mAh g−1 at C/20 rate in Na/Na-NCM half cell. The fabricated SIFC in coin cell configuration delivers a specific capacity of 74.6 mAh g−1 at C/20 rate, with 40% of the initial discharge capacity delivered after 100 cycles at C/20 and the columbic efficiency is more than 90%. The coin cell in full cell configuration displays reasonable performance at the rates of C/20 to 3C indicating the capability of high rate performance of anode and cathode materials. The first discharge capacity of fabricated SIFC in prismatic configuration is 2.16Ah.

The impact of heat stress coinciding with reproductive stages in winter canola was studied using walk‐in controlled environment chambers and field‐based tents. Six different cultivars (46W94, Edimax CL, Mercedes, Popular, DKW44‐10 and DKW46‐15) were used in both the experiments following a split‐plot design. Under controlled environment chambers, all six cultivars were exposed to HDT (day/night; 34/15°C), HNT (23/20°C), HDNT (34/20°C) and control (23/15°C) conditions for 14 days coinciding with flowering. Under field conditions, custom built ‘heat tents’ were used to impose heat stress starting seven days after 50% of flowering till maturity. The results demonstrated that HDT and HDNT induced significant impact on floral morphology, extreme levels of floral sterility and complete yield loss with two weeks of stress exposure during flowering. However, biomass, seed weight and oil concentration at maturity were either significantly increased or unchanged which demonstrated significant post‐stress phenotypic plasticity in canola to overcome damage caused by short episode of HDT and HDNT during flowering. The long duration heat stress under field conditions recorded significant decrease in yield parameters and oil concentration in the canola cultivars. Incorporating greater post‐stress phenotypic plasticity will help develop canola as an ideal alternative crop under future climates associated with enhanced frequency of short heat stress episodes coinciding with critical reproductive stages.

Canopy temperature, detected by thermal imaging, is a good predictor of rice yield performance under drought and shows genetic variation in an association mapping panel., Drought-stressed plants display reduced stomatal conductance, which results in increased leaf temperature by limiting transpiration. In this study, thermal imaging was used to quantify the differences in canopy temperature under drought in a rice diversity panel consisting of 293 indica accessions. The population was grown under paddy field conditions and drought stress was imposed for 2 weeks at flowering. The canopy temperature of the accessions during stress negatively correlated with grain yield (r= –0.48) and positively with plant height (r=0.56). Temperature values were used to perform a genome-wide association (GWA) analysis using a 45K single nucleotide polynmorphism (SNP) map. A quantitative trait locus (QTL) for canopy temperature under drought was detected on chromosome 3 and fine-mapped using a high-density imputed SNP map. The candidate genes underlying the QTL point towards differences in the regulation of guard cell solute intake for stomatal opening as the possible source of temperature variation. Genetic variation for the significant markers of the QTL was present only within the tall, low-yielding landraces adapted to drought-prone environments. The absence of variation in the shorter genotypes, which showed lower leaf temperature and higher grain yield, suggests that breeding for high grain yield in rice under paddy conditions has reduced genetic variation for stomatal response under drought.

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.

Extreme weather events, especially heat waves, have become more frequent with global warming. High temperature significantly affects world food security by decreasing crop yield. Rice is intensively planted in tropical and subtropical areas in Asia, where high temperature has become a major factor affecting rice production. Rice is sensitive to high temperature, especially at booting and flowering stages. Rice varieties tolerant of high temperature are rare, and only a few heat-tolerant rice varieties have been identified. High temperature at booting and flowering stages causes sterile pollen, decreased pollen shedding, and poor pollen germination, which finally lead to a yield decrease. Heat-tolerant QTLs have been identified in different studies, but new breeding lines with considerable heat tolerance have not been bred using identified heat-tolerance donors and QTLs. Research on heat-tolerant donor identification, QTL mapping, gene cloning, and large-scale phenotyping technology is important for developing heat-tolerant rice varieties.

Background Lipidomics plays an important role in understanding plant adaptation to different stresses and improving our knowledge of the genes underlying lipid metabolism. Lipidomics involves lipid extraction, sample preparation, mass spectrometry analysis, and data interpretation. One of the practical challenges for large-scale lipidomics studies on plant leaves is the requirement of an efficient and rapid extraction method. Results A single-extraction method with a polar solvent mixture gives results comparable to a widely used, multi-extraction method when tested on both Arabidopsis thaliana and Sorghum bicolor leaf tissue. This single-extraction method uses a mixture of 30 parts chloroform, 25 parts isopropanol, 41.5 parts methanol, and 3.5 parts water (v/v/v/v) and a 24-h extraction time. Neither inclusion of ammonium acetate nor inclusion of acetic acid increased extraction efficiency. Conclusions The extract produced by this method can be used for analysis by mass spectrometry without a solvent evaporation step. The amount of lipid extracted, including phosphatidic acid, is comparable to widely used, more labor-intensive methods. The single-extraction protocol is less laborious, reducing the potential for human error. Electronic supplementary material The online version of this article (10.1186/s13007-018-0282-y) contains supplementary material, which is available to authorized users.

Phenotypic plasticity of plants in response to environmental changes is important for adapting to changing climate. Less attention has been paid to exploring the advantages of phenotypic plasticity in resource-rich environments to enhance the productivity of agricultural crops. Here, we examined genetic variation for phenotypic plasticity in indica rice (Oryza sativa L.) across two diverse panels: (1) a Phenomics of Rice Adaptation and Yield (PRAY) population comprising 301 accessions; and (2) a Multi-parent Advanced Generation Inter-Cross (MAGIC) indica population comprising 151 accessions. Altered planting density was used as a proxy for elevated atmospheric CO2 response. Low planting density significantly increased panicle weight per plant compared with normal density, and the magnitude of the increase ranged from 1.10 to 2.78 times among accessions for the PRAY population and from 1.05 to 2.45 times for the MAGIC population. Genome-wide-association studies validate three Environmental Responsiveness (ER) candidate alleles (qER1-3) that were associated with relative response of panicle weight to low density. Two of these alleles were tested in 13 genotypes to clarify their biomass responses during vegetative growth under elevated CO2 in Japan. Our study provides evidence for polymorphisms that control rice phenotypic plasticity in environments that are rich in resources such as light and CO2 .

Heat stress is a major constrain to sustain rice production and grain quality. Rising atmospheric [CO2] is predicted to increase photosynthesis resulting in higher biomass and yield. Conversely, both elevated (e[CO2]) and heat stress (HT) are documented to deteriorate grain quality traits in rice. However, interactive effect of e[CO2] + HT on rice grain yield, quality traits and particularly mineral composition under natural field condition in tropical environments are limited. Independent field experiments were conducted to assess the potential impact of e[CO2] alone and in combination with HT on grain yield, quality traits and mineral composition of two rice cultivars Nerica-L-44 (heat tolerant) and Indian basmati rice variety Pusa 1121, using field based open top chamber (OTC) facility. Elevated [CO2] significantly influenced grain quality traits by increasing chalkiness (69–83%), amylose content (18–37%), decreasing protein content by 4% and altering grain mineral nutrient composition across the cultivars. Proportion of chalky grains was further increased in Nerica-L-44 and Pusa 1121 under e[CO2] + HT interaction. Correlation analysis revealed negative relationship of grain minerals with chalkiness and amylose content. In summary, independent exposure of rice to e[CO2] reduced grain quality and e[CO2] + HT further increased the negative effects on grain nutrient and quality.

For the development of sodium ion secondary batteries, performance improvement in the positive electrode is the main area of research in recent times. Enhancement in electrochemical performance of Na0.44MnO2(NMO) material as a positive electrode material for sodium ion secondary batteries plays a vital role. In this work, the NMO orthorhombic compound was prepared through sol–gel auto combustion process and characterized. Its electrochemical properties are investigated and discussed. The material displays a discharge capacity of about 102.5 mAh/g at a low current rate (C/20), which decreases to 36.75 mAh/g at a relatively higher rate (2C). The capacity retention at C/10 after 50 cycles is 85.7%. The evaluation of Na-ion diffusion coefficients (DNa+) in NMO is accomplished by potentiostatic intermittent titration technique (PITT) test and galvanostatic intermittent titration technique (GITT) test. The obtained values for the Na-ion diffusivity are ranging between 10−14 and 10−15 cm2 s−1.

Rice (Oryza sativa L.) plays a key role in sustaining global food security; however, rice production also accounts for a significant proportion of global methane (CH4) emissions, a major greenhouse gas involved in altering global climate. Many previous studies have quantified the proportion of CH4 emissions by independently evaluating factors such as soil texture and cultivars – an approach that has led to potentially biased estimates of their actual contribution to total emissions. Most of these studies have not considered the influence of the preceding crop or growing-season weather that could lead to a significant variation in carbon budgets. The main objective of this study was to identify the key edaphic, cultivar, and environmental factors and determine their proportional contributions towards CH4 emissions in direct-seeded, rice-based cropping systems. A multiple regression model was developed to quantify CH4 emissions as a function of temperature (both day and night independently and in combination) and other weather variables, soil (silt-loam-surface-textured Albaqualf and clay-surface-textured Epiaquert), cultivar (conventional and hybrid), and cropping system (rice-rice and soybean [Glycine max L.]-rice). Results showed that (i) the Albaqualf emitted 211% more CH4-C than the Epiaquert (P

Identifying a reliable and robust temperature threshold inducing rice spikelet sterility under field conditions involving cultivars with highly varying phenology has been a major limitation. This challenge has been a consistent bottleneck in devising a phenotyping strategy for rice breeders and to accurately estimate heat stress impacts by the climate and crop modeling communities. In an attempt to address this challenge, we used 292 diverse indica cultivars, recorded 15 min air temperature data during the key flowering period across wet season and two consecutive dry (summer) seasons. We identified 33 °C as the critical threshold beyond which large sterility increases were observed. This is the first report that demonstrates the need to consider cultivar and seasonal fixed effects in a regression model framework to derive meaningful temperature thresholds. We find that an additional growing degree hour (GDH) above 33 °C is associated with a 0.26 percentage point increase in sterility. The average and maximum exposures above this threshold in the sample data are 13.0 and 46.5 h, respectively, corresponding to a 3.4 and 12.0 percentage point increase in sterility. We simulate warming impacts between 0.5–2.0 °C increase in daily temperatures, which increases sterility between 2.9–13.1 percentage points for the dry summer season and 0.2–3.2 percentage points for the wet season. Evidence for threshold heterogeneity across different sterility classes – low, medium and high sterility cultivar groups is tested and we find limited evidence for this extension of the model. The identified threshold can be utilized by breeders to test contrasting cultivars or segregating mapping populations in an unbiased set up and for precise heat stress impact modeling exercises. Heat sensitivity analysis indicated substantial genetic variability for heat induced spikelet sterility, providing ample evidence for producer adaptation to a warming climate by developing and switching to more heat stress resilient cultivars.

Global warming is projected to cause yield losses due to heat-induced spikelet sterility (HISS) in hot, vulnerable rice-growing regions, but reports documenting HISS at a regional level in the tropics are very limited. As a case study, HISS at flowering stage was surveyed under field conditions using local popular varieties in Savannakhet, Laos, and Tamil Nadu, India, during the dry season. At the field site in Savannakhet, sterility in variety Thadokkham1 (TDK1) was 10.8% when the maximum average temperature at heading was 32.9 °C, which increased to 23.3% at 37.3 °C. When plots were covered with a shading net, solar radiation was reduced by 60% at heading, which significantly reduced sterility to 10.0%. Panicle temperature estimates produced with a micrometeorology model revealed that shading during the hours when flowering occurs decreased panicle temperature by 2.2–2.6 °C. At the field sites in Tamil Nadu, sterility of variety Coimbatore 51 (CO51) was highly correlated with the maximum temperature at heading; sterility was around 5–10% when maximum average temperature was below 36.5 °C, which increased to 33.4% at 38.0 °C. Marking of opened spikelets at hourly intervals allowed us to detect increases in sterility as temperature increased from early morning until noon. We conclude that HISS at flowering stage can occur in local popular varieties grown in Savannakhet and Tamil Nadu during the hot, dry season. Effective protocols such as using a shading net and hourly marking of open spikelets are useful approaches to quantifying HISS during flowering stage across hot and potential heat-vulnerable rice-growing regions.

Background and Aim Water is an increasingly scarce resource while some crops, such as paddy rice, require large amounts of water to maintain grain production. A better understanding of rice drought adaptation and tolerance mechanisms could help to reduce this problem. There is evidence of a possible role of root-associated fungi in drought adaptation. Here, we analyzed the endospheric fungal microbiota composition in rice and its relation to plant genotype and drought. Methods Fifteen rice genotypes (Oryza sativa ssp. indica) were grown in the field, under well-watered conditions or exposed to a drought period during flowering. The effect of genotype and treatment on the root fungal microbiota composition was analyzed by 18S ribosomal DNA high throughput sequencing. Grain yield was determined after plant maturation. Results There was a host genotype effect on the fungal community composition. Drought altered the composition of the root-associated fungal community and increased fungal biodiversity. The majority of OTUs identified belonged to the Pezizomycotina subphylum and 37 of these significantly correlated with a higher plant yield under drought, one of them being assigned to Arthrinium phaeospermum. Conclusion This study shows that both plant genotype and drought affect the root-associated fungal community in rice and that some fungi correlate with improved drought tolerance. This work opens new opportunities for basic research on the understanding of how the host affects microbiota recruitment as well as the possible use of specific fungi to improve drought tolerance in rice.

High temperature has a pronounced effect on grain yield and quality in rice. Climate change has increased night temperature more than day temperature in many parts of the world. How rice responds to high night-time temperature (HNT) is largely unknown. This study presents the first effort to assess the response of tropical hybrid rice to HNT. Six commercial tropical hybrid rice cultivars together with a tolerant (N22-aus) and a susceptible (Gharib-indica) genotype were evaluated under control temperature (23 °C) and HNT (29 °C) starting from panicle initiation until maturity under field conditions at the International Rice Research Institute during the dry (DS) and wet (WS) seasons of 2013. Overall, HNT significantly decreased grain yield of Gharib and all tested hybrids across both seasons, with less average reduction in the DS (13.4%) than in the WS (18.6%). Among the yield components, spikelets m−2 most significantly contributed to yield variation under control and/or HNT during both DS and WS followed by grain weight, while the contribution of seed-set was low and season-specific. Grain quality in most hybrids was also strongly affected by HNT, with decreased head rice yield, increased chalkiness and reduced grain width. Given this vulnerability to HNT, there is an urgent need to explore options for improving the adaptation of rice hybrids to increasingly warmer nights.

Improving the genetic yield potential (YP) of tropical, irrigated rice varieties is a priority objective of rice breeding programs worldwide in the interest of achieving food security and maintaining political stability. But YP has stagnated at about 10 Mg ha−1 since the Green Revolution. We present a survey of researchers' current top yields across different environments and countries, experimentally investigate YP-related traits and radiation use efficiency (RUE) of 12 elite materials, and use a simple model to explore traits that would raise the yield ceiling. The survey indicated that maximal grain yield is between 5 and 12 Mg ha−1 depending on radiation during flowering and grain filling. The experiments conducted in several environments in the Philippines indicated that (1) different morphologies in terms of panicle number and size and leaf size lead to similar YP due to trait–trait compensation, and (2) differences in RUE are partly attributable to variation in terminal senescence which is strongly environment dependent. Simulations thus focused on post-floral physiological processes, namely dynamics of light interception, carbon assimilation and maintenance burden. Scenarios of different degree of stay-green indicated that terminal senescence is essential to limit N requirements and maintenance burden, but partial stay-green would strongly benefit RUE and YP, particularly if accompanied with increased leaf photosynthetic capacity. The need to increase pre-floral C and N reserves for grain filling is discussed, resulting in a concept to refine current ideotypes such as IRRI's New Plant Type and China's Super Hybrid Rice. In conclusion, current best tropical breeding products do not have higher YP than some varieties dating 30–40 years, and new concepts are needed in rice breeding. Breeding for such plants should be done under high N inputs.

High night temperature (HNT) significantly influences rice grain filling dynamics. A novel phenotyping approach using chlorophyll fluorescence was employed to track changes in the optical properties of maturing rice panicles exposed to control and HNT. Two contrasting rice genotypes, Gharib (HNT sensitive) and N22 (highly tolerant), were exposed to control (23 °C) and HNT (29 °C), from panicle initiation till maturity. Changes in the optical properties of rice panicles throughout maturity were evaluated under field conditions by measuring (i) effective quantum yield of photosystem II efficiency ( Φ II ), (ii) steady-state chlorophyll fluorescence ( F S ) and (iii) ratio of emitted chlorophyll fluorescence at 690 and 735 nm, under excitation at 435 nm ( F 690 / F 735 ). Numerous vegetative indices (Vis) were correlated with fluorescence measurements to prove the accuracy of the phenotyping method. Φ II was selected as the most potent fluorescence parameter (i) to track changing optical properties of maturing rice panicles under both control and HNT and (ii) to estimate the elusive change point initiating rice panicle senescence. Detection of Φ II change point allows for larger genetic diversity scans under field conditions and for identifying novel donors for increasing rice yields and incorporating resilient strategies to reduce impact of HNT stress on grain-filling.

Heat and drought stress are projected to become major challenges to sustain rice (Oryza sativa L.) yields with global climate change. Both stresses lead to yield losses when they coincide with flowering. A significant knowledge gap exists in the mechanistic understanding of the responses of rice floral organs that determine reproductive success under stress. Our work connects the metabolomic and transcriptomic changes in anthers, pistils before pollination and pollinated pistils in a heat-tolerant (N22) and a heat-sensitive (Moroberekan) cultivar. Systematic analysis of the floral organs revealed contrasts in metabolic profiles across anthers and pistils. Constitutive metabolic markers were identified that can define reproductive success in rice under stress. Six out of nine candidate metabolites identified by intersection analysis of stressed anthers were differentially accumulated in N22 compared with Moroberekan under non-stress conditions. Sugar metabolism was identified to be the crucial metabolic and transcriptional component that differentiated floral organ tolerance or susceptibility to stress. While susceptible Moroberekan specifically showed high expression of the Carbon Starved Anthers (CSA) gene under combined heat and drought, tolerant N22 responded with high expression of genes encoding a sugar transporter (MST8) and a cell wall invertase (INV4) as markers of high sink strength.

Gradual and abrupt changes in temperature under current and future climates pose a serious threat to ecological diversity and in sustaining global food security. Plants possess a robust network of thermal sensors to program their metabolic and hormonal framework, providing acclimation to short-term abrupt fluctuations or adaptation to gradual temperature change. Several cellular thermosensors are reported in plants and understanding their mode of operation in a potentially coordinated framework continues to be a persistent challenge. Despite growing insight into the molecular control of thermal perception, physiological significance of plant thermal responses under a complex interaction with other environmental cues is largely unaddressed. Plant thermal perception and signaling could be similar across growth habits such as herbaceous to perennial woody species while developmental transitions such as vegetative to reproductive stage, influenced by their immediate microclimate, are generally altered across growth habits. The overall aim is to connect the knowledge gained with thermal perception and the signaling that drives plant responses, with major focus on the latter.

Resilience of rice cropping systems to potential global climate change will partly depend on the temperature tolerance of pollen germination (PG) and tube growth (PTG). Pollen germination of high temperature-susceptible Oryza glaberrima Steud. (cv. CG14) and Oryza sativa L. ssp. indica (cv. IR64) and high temperature-tolerant O. sativa ssp. aus (cv. N22), was assessed on a 5.6–45.4 °C temperature gradient system. Mean maximum PG was 85% at 27 °C with 1488 μm PTG at 25 °C. The hypothesis that in each pollen grain, the minimum temperature requirements (Tn) and maximum temperature limits (Tx) for germination operate independently was accepted by comparing multiplicative and subtractive probability models. The maximum temperature limit for PG in 50% of grains (Tx(50)) was the lowest (29.8 °C) in IR64 compared with CG14 (34.3 °C) and N22 (35.6 °C). Standard deviation (sx) of Tx was also low in IR64 (2.3 °C) suggesting that the mechanism of IR64's susceptibility to high temperatures may relate to PG. Optimum germination temperatures and thermal times for 1 mm PTG were not linked to tolerating high temperatures at anthesis. However, the parameters Tx(50) and sx in the germination model define new pragmatic criteria for successful and resilient PG, preferable to the more traditional cardinal (maximum and minimum) temperatures.

Night temperature (NT) increases faster than day temperature with global warming and this may have strong implications for crop yield. One of the assumptions is the increase in night respiration and thus the increase in carbon losses over time. Some rice cultivars (indica, aus and japonica types) were grown in the field in the Philippines and in heated greenhouses in Montpellier, France, to quantify the response of respiration to increased NT and its implication at crop level. Increased NT by 3.8 and 5.4 °C over the whole crop cycle in two greenhouse experiments and by 1.9 °C in the field from 33 days after transplanting up to maturity using a free-air-controlled enhancement increased night respiration rate significantly. Overall, the cost in CH 2 O of night respiration over crop duration was 17 to 20% (field) and 8 to 18% (greenhouse) of the potential shoot dry matter (including that lost by respiration). Additional respiratory burden due to increased NT was only 1 to 7% of the potential shoot dry matter at maturity, and was not associated with significant loss in additional dry matter. The absence of any dry matter reduction with increased NT within indica cultivars questions the assumptions of recent papers.

Genetic analysis of grain yield and its components in a rice diversity panel identified genetic loci that regulate water deficit tolerance during the reproductive stage., A diversity panel comprising of 296 indica rice genotypes was phenotyped under non-stress and water-deficit stress conditions during the reproductive stage in the 2013 and 2014 dry seasons (DSs) at IRRI, Philippines. We investigated the genotypic variability for grain yield, yield components, and related traits, and conducted genome-wide association studies (GWAS) using high-density 45K single nucleotide polymorphisms. We detected 38 loci in 2013 and 64 loci in 2014 for non-stress conditions and 69 loci in 2013 and 55 loci in 2014 for water-deficit stress. Desynchronized flowering time confounded grain yield and its components under water-deficit stress in the 2013 experiment. Statistically corrected grain yield and yield component values using days to flowering helped to detect 31 additional genetic loci for grain yield, its components, and the harvest index in 2013. There were few overlaps in the detected loci between years and treatments, and when compared with previous studies using the same panel, indicating the complexity of yield formation under stress. Nevertheless, our analyses provided important insights into the potential links between grain yield with seed set and assimilate partitioning. Our findings demonstrate the complex genetic architecture of yield formation and we propose exploring the genetic basis of less complex component traits as an alternative route for further yield enhancement.

Water scarcity and the increasing severity of water deficit stress are major challenges to sustaining irrigated rice (Oryza sativa) production. Despite the technologies developed to reduce the water requirement, rice growth is seriously constrained under water deficit stress compared with other dryland cereals such as wheat (Triticum aestivum). We exposed rice cultivars with contrasting responses to water deficit stress and wheat cultivars well adapted to water-limited conditions to the same moisture stress during vegetative growth to unravel the whole-plant (shoot and root morphology) and organ/tissue (root anatomy) responses. Wheat cultivars followed a water-conserving strategy by reducing specific leaf area and developing thicker roots and moderate tillering. In contrast, rice ‘IR64’ and ‘Apo’ adopted a rapid water acquisition strategy through thinner roots under water deficit stress. Root diameter, stele and xylem diameter, and xylem number were more responsive and varied with different positions along the nodal root under water deficit stress in wheat, whereas they were relatively conserved in rice cultivars. Increased metaxylem diameter and lower metaxylem number near the root tips and exactly the opposite phenomena at the root-shoot junction facilitated the efficient use of available soil moisture in wheat. Tolerant rice ‘Nagina 22’ had an advantage in root morphological and anatomical attributes over cultivars IR64 and Apo but lacked plasticity, unlike wheat cultivars exposed to water deficit stress. The key traits determining the adaptation of wheat to dryland conditions have been summarized and discussed.

Flooded rice is grown across wide geographic boundaries from as far north as Manchuria and as far south as Uruguay and New South Wales, primarily because of its adaptability across diverse agronomic and climatic conditions. Salt-stress damage, a common occurrence in delta and coastal rice production zones, could be heightened by the interactions between high temperature and relative humidity (vapor pressure deficit--VPD). Using temporal and spatial observations spanning 107 seasons and 19 rice-growing locations throughout India with varying electrical conductivity (EC), including coastal saline, inland saline, and alkaline soils, we quantified the proportion of VPD inducing salinity damage in rice. While controlling for time-invariant factors such as trial locations, rice cultivars, and soil types, our regression analysis indicates that EC has a nonlinear detrimental effect on paddy rice yield. Our estimates suggest these yield reductions become larger at higher VPD. A one standard deviation (SD) increase in EC from its mean value is associated with 1.68% and 4.13% yield reductions at median and maximum observed VPD levels, respectively. Yield reductions increase roughly sixfold when the one SD increase is taken from the 75th percentile of EC. In combination, high EC and VPD generate near catastrophic crop loss as predicted yield approaches zero. If higher VPD levels driven by global warming materialize in conjunction with rising sea levels or salinity incursion in groundwater, this interaction becomes an important and necessary predictor of expected yield losses and global food security.

Glutaredoxins (GRXs) modulate redox-dependent signaling pathways and have emerged as key mediators in plant responses to environmental stimuli. Here we report that RNAi-mediated suppression of Oryza sativa GRXS17 (OsGRXS17) improved drought tolerance in rice. Gene expression studies showed that OsGRXS17 was present throughout the plant and that transcript abundance increased in response to drought stress and abscisic acid (ABA) treatment. Localization studies, utilizing GFP-OsGRXS17 fusion proteins, indicated that OsGRXS17 resides in both the cytoplasm and the nuclear envelope. Under drought stress conditions, rice plants with reduced OsGRXS17 expression showed lower rates of water loss and stomatal conductance, higher relative water content, and enhanced survival compared to wild-type controls. Further characterization of the OsGRXS17 down-regulated plants revealed an elevation in H2O2 production within the guard cells, increased sensitivity to ABA, and a reduction in stomatal apertures. The findings demonstrate a critical link between OsGRXS17, the modulation of guard cell H2O2 concentrations, and stomatal closure, expanding our understanding of the mechanisms governing plant responses to drought.

Highlight qEMF3, a novel QTL for the early-morning flowering trait to mitigate heat-induced spikelet sterility at flowering in rice, was identified using a wild rice, Oryza officinalis, as a genetic resource., A decline in rice (Oryza sativa L.) production caused by heat stress is one of the biggest concerns resulting from future climate change. Rice spikelets are most susceptible to heat stress at flowering. The early-morning flowering (EMF) trait mitigates heat-induced spikelet sterility at the flowering stage by escaping heat stress during the daytime. We attempted to develop near-isogenic lines (NILs) for EMF in the indica-type genetic background by exploiting the EMF locus from wild rice, O. officinalis (CC genome). A stable quantitative trait locus (QTL) for flower opening time (FOT) was detected on chromosome 3. A QTL was designated as qEMF3 and it shifted FOT by 1.5–2.0h earlier for cv. Nanjing 11 in temperate Japan and cv. IR64 in the Philippine tropics. NILs for EMF mitigated heat-induced spikelet sterility under elevated temperature conditions completing flower opening before reaching 35°C, a general threshold value leading to spikelet sterility. Quantification of FOT of cultivars popular in the tropics and subtropics did not reveal the EMF trait in any of the cultivars tested, suggesting that qEMF3 has the potential to advance FOT of currently popular cultivars to escape heat stress at flowering under future hotter climates. This is the first report to examine rice with the EMF trait through marker-assisted breeding using wild rice as a genetic resource.

Identifying CO(2) responsive genotypes is a major target for enhancing crop productivity under future global elevated atmospheric CO(2) concentration ([CO(2)]). However, [CO(2)]-fumigation facilities are extremely expensive and are not easily accessible, and are limited in space for large-scale screening. Hence, reliable donors for initiating [CO(2)]-responsive breeding programs are not in place for crops, including rice. We propose a simple and novel phenotyping method for identifying [CO(2)]-responsive genotypes, and quantify the responsiveness to low planting density over 4-year trials across both temperate and tropical conditions. Panicle number per plant is the key determinant of grain yield and hence was the focus trait across all our trials. In temperate climate, a 3-season field screening using 127 diverse rice genotypes and employing two planting densities (normal and low density) was conducted. Two japonica genotypes were selected based on their higher responsiveness to low planting density as candidates for validating the proposed phenotyping protocol as a pre-screen for [CO(2)]-responsiveness. The approach using the two selected candidates and three standard genotypes was confirmed using a free-air CO(2) enrichment facility and temperature gradient chambers under elevated [CO(2)]. In tropical climate, we grew three rice cultivars, previously identified for their [CO(2)]-responsiveness, at two planting densities. The experiments provided confirmation that responsiveness to low planting density was correlated with that of [CO(2)]-responsiveness across both the temperate and tropical conditions. The planting density would be useful pre-screening method for testing large panels of diverse germplasm at low cost complemented by available CO(2) -control facilities for final validation of candidates from the pre-screens.

Options to increase resource use efficiency and climatic yield potential of locally adapted super rice hybrids including combined water, nutrient and other agronomic management are limited. Hence, the aim of our three-year (six seasons) experiments during early-season (ESR; Luliangyou996) and late-season (LSR; C-liangyou396) rice in southern China was to identify key yield parameters and optimum resource use options to enhance the crop's climatic yield potential. Grain yield averaged across all three years with effective N management combined with post-anthesis shallow wetting and drying was 32.8% and 37.1% higher than the normal farmers’ practice in Liuyang County in ESR and LSR, respectively. More spikelets m −2 were the key to achieving high yield potential, further supported by increased leaf area index and high radiation interception and internal use efficiency. The split application of nitrogen in combination with shallow wetting and drying allowed for better N uptake, use efficiency and partitioning, leading to enhanced biomass and yield. The high yield potential, however, was not just a function of genetics and management but also depended on the climatic conditions prevailing, particularly temperature and radiation. In ESR, lower temperature during vegetative stage reduced overall biomass and sink size while subsequent higher temperature reduced the total grain filling period by 17 days compared with LSR, indicating a climatic condition-driven decline in yield potential rather than lower genetic potential of the super hybrids. A lack of correlation of spikelets panicle −1 and spikelets m −2 with grain-filling percentage in LSR provided evidence that a larger sink does not necessarily result in poor grain filling when sufficient time and assimilates for grain filling are provided, which is more climate dependent. Our work highlights the benefits of integrating nutrient, water and agronomic management options to achieve high NUE and grain yield.

High night-time temperature (HNT) disturbs processes of both assimilate production (source) and assimilate accumulation (sink), and as a result substantially reduces yields of cereal crops. There have been reports that increasing nitrogen application can alleviate the negative impact of high-temperature stress on yield in rice (Oryza sativa L.). However, little is known about the interactive effect of HNT and nitrogen (N) supply on rice grain yield and its underlying source-sink relationships. We conducted two field experiments at the International Rice Research Institute in both the dry (DS) and wet (WS) season of 2012, in which three cultivars with contrasting responses to HNT were grown under two levels of night-time temperature and two levels of N application. HNT significantly decreased grain yield of cv. Gharib at both N levels and in both seasons, while grain yield of cv. PSBRc4 was significantly reduced by HNT at the higher N level only. Among the yield components, grain weight was consistently reduced by HNT in all three cultivars across two seasons while spikelets m−2 and seed-set were affected by HNT during DS and WS, respectively. In most cases, higher N application reduced grain yield and its components. Thus, in our study, increasing the total N fertilizer did not alleviate the adverse effects of HNT on rice yield. Using a novel modelling approach that quantifies source-sink relationships during grain filling, we found that increased nitrogen did not alleviate the negative impact of HNT on source-sink interactions during grain growth across cultivars and seasons. Nevertheless, the model showed that there were significant differences among cultivars in grain filling duration, grain filling rate and total sink size, modulated by their source-sink relationship in response to HNT, suggesting that breeding programs should select for sink-related traits to improve rice tolerance to HNT.

High night temperature (HNT) is a major constraint to sustaining global rice production under future climate. Physiological and biochemical mechanisms were elucidated for HNT-induced grain yield and quality loss in rice. Contrasting rice cultivars (N22, tolerant; Gharib, susceptible; IR64, high yielding with superior grain quality) were tested under control (23°C) and HNT (29°C) using unique field-based tents from panicle initiation till physiological maturity. HNT affected 1000 grain weight, grain yield, grain chalk and amylose content in Gharib and IR64. HNT increased night respiration (Rn) accounted for higher carbon losses during post-flowering phase. Gharib and IR64 recorded 16 and 9% yield reduction with a 63 and 35% increase in average post-flowering Rn under HNT, respectively. HNT altered sugar accumulation in the rachis and spikelets across the cultivars with Gharib and IR64 recording higher sugar accumulation in the rachis. HNT reduced panicle starch content in Gharib (22%) and IR64 (11%) at physiological maturity, but not in the tolerant N22. At the enzymatic level, HNT reduced sink strength with lower cell wall invertase and sucrose synthase activity in Gharib and IR64, which affected starch accumulation in the developing grain, thereby reducing grain weight and quality. Interestingly, N22 recorded lower Rn-mediated carbon losses and minimum impact on sink strength under HNT. Mechanistic responses identified will facilitate crop models to precisely estimate HNT-induced damage under future warming scenarios.

Breeding programs with the aim to enhance yield productivity under abiotic stress conditions during the reproductive stage of crops is a top priority in the era of climate change. However, the choice of exploring stay-green or senescence phenotypes, which represent an opposing physiological bearing, are explored in cereal breeding programs for enhanced yield stability to a different extent. Thus, the consideration of stay-green or senescence phenotypes is still an ongoing debate and has not been comprehensively addressed. In this review, we provide arguments for designing a target phenotype needed to encounter mitigate abiotic stresses during pre- and post-anthesis in cereals with a focus on hormonal balances regulating stay-green phenotype versus remobilization. The two major hypothesis for grain yield improvement are (i) the importance of the stay-green trait to elevate grain number under pre-anthesis and anthesis stress and (ii) fine tuning the regulatory and molecular physiological mechanisms to accelerate nutrient remobilization to optimize grain quality and seed weight under post-anthesis stress. We highlight why a cautious balance in the phenotype design is essential. While stay-green phenotypes promise to be ideal for developing stress-tolerant lines during pre-anthesis and fertilization to enhance grain number and yield per se, fine-tuning efficient remobilizing behaviour during seed filling might optimize grain weight, grain quality and nutrient efficiency. The proposed model provides novel and focused directions for cereal stress breeding programs to ensure better seed-set and efficient grain-filling in cereals under terminal drought and heat stress exposure.

Rice is one of the main food crops in the world. In the near future, yield is expected to be under pressure due to unfavorable climatic conditions, such as increasing temperatures. Therefore, improving rice germplasm in order to guarantee rice production under harsh environmental conditions is of top priority. Although many physiological studies have contributed to understanding heat responses during anthesis, the most heat-sensitive stage, molecular data are still largely lacking. In this study, an RNA-sequencing approach of heat- and control-treated reproductive tissues during anthesis was carried out using N22, one of the most heat-tolerant rice cultivars known to date. This analysis revealed that expression of genes encoding a number of transcription factor families, together with signal transduction and metabolic pathway genes, is repressed. On the other hand, expression of genes encoding heat shock factors and heat shock proteins was highly activated. Many of these genes are predominantly expressed at late stages of anther development. Further physiological experiments using heat-tolerant N22 and two sensitive cultivars suggest that reduced yield in heat-sensitive plants may be associated with poor pollen development or production in anthers prior to anthesis. In parallel, induction levels of a set of heat-responsive genes in these tissues correlated well with heat tolerance. Altogether, these findings suggest that proper expression of protective chaperones in anthers is needed before anthesis to overcome stress damage and to ensure fertilization. Genes putatively controlling this process were identified and are valuable candidates to consider for molecular breeding of highly productive heat-tolerant cultivars. Fil: Gonzalez Schain, Nahuel Damian. Università degli Studi di Milano; Italia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Biología Molecular y Celular de Rosario. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Instituto de Biología Molecular y Celular de Rosario; Argentina Fil: Dreni, Ludovico. Università degli Studi di Milano; Italia. Shanghai Jiao Tong University; China Fil: Lawas, Lovely M. F.. International Rice Research Institute; Filipinas Fil: Galbiati, Massimo. Università degli Studi di Milano; Italia Fil: Colombo, Lucia. Università degli Studi di Milano; Italia Fil: Heuer, Sigrid. Australian Centre For Plant Functional Genomics; Australia Fil: Jagadish, Krishna S. V.. International Rice Research Institute; Filipinas Fil: Kater, Martin M.. Università degli Studi di Milano; Italia

Global warming causes night temperature (NT) to increase faster than day temperature in the tropics. According to crop growth models, respiration incurs a loss of 40-60% of photosynthate. The thermal sensitivity of night respiration (R(n)) will thus reduce biomass. Instantaneous and acclimated effects of NT on R(n) of leaves and seedlings of two rice cultivars having a variable level of carbohydrates, induced by exposure to different light intensity on the previous day, were investigated. Experiments were conducted in a greenhouse and growth chambers, with R(n) measured on the youngest fully expanded leaves or whole seedlings. Dry weight-based R(n) was 2.6-fold greater for seedlings than for leaves. Leaf R(n) was linearly related to starch (positive intercept) and soluble sugar concentration (zero intercept). Increased NT caused higher R(n) at a given carbohydrate concentration. The change of R(n) at NT increasing from 21 °C to 31 °C was 2.4-fold for the instantaneous response but 1.2- to 1.7-fold after acclimation. The maintenance component of R(n) (R(m)'), estimated by assimilate starvation, averaged 28% in seedlings and 34% in leaves, with no significant thermal effect on this ratio. The acclimated effect of increased NT on R(m)' across experiments was 1.5-fold for a 10 °C increase in NT. No cultivar differences were observed in R(n) or R(m)' responses. The results suggest that the commonly used Q10=2 rule overestimates thermal response of respiration, and R(n) largely depends on assimilate resources.

Background Climate change is affecting rice production in many countries. Developing new rice varieties with heat tolerance is an essential way to sustain rice production in future global warming. We have previously reported four quantitative trait loci (QTLs) responsible for rice spikelet fertility under high temperature at flowering stage from an IR64/N22 population. To further explore additional QTL from other varieties, two bi-parental F2 populations and one three-way F2 population derived from heat tolerant variety Giza178 were used for indentifying and confirming QTLs for heat tolerance at flowering stage. Results Four QTLs (qHTSF1.2, qHTSF2.1, qHTSF3.1 and qHTSF4.1) were identified in the IR64/Giza178 population, and two other QTLs (qHTSF6.1 and qHTSF11.2) were identified in the Milyang23/Giza178 population. To confirm the identified QTLs, another three-way-cross population derived from IR64//Milyang23/Giza178 was genotyped using 6K SNP chips. Five QTLs were identified in the three-way-cross population, and three of those QTLs (qHTSF1.2, qHTSF4.1 and qHTSF6.1) were overlapped with the QTLs identified in the bi-parental populations. The tolerance alleles of these QTLs were from the tolerant parent Giza178 except for qHTSF3.1. The QTL on chromosome 4 (qHTSF4.1) is the same QTL previously identified in the IR64/N22 population. Conclusion The results from different populations suggest that heat tolerance in rice at flowering stage is controlled by several QTLs with small effects and stronger heat tolerance could be attained through pyramiding validated heat tolerance QTLs. QTL qHTSF4.1 was consistently detected across different genetic backgrounds and could be an important source for enhancing heat tolerance in rice at flowering stage. Polymorphic SNP markers in these QTL regions can be used for future fine mapping and developing SNP chips for marker-assisted breeding. Electronic supplementary material The online version of this article (doi:10.1186/s12863-015-0199-7) contains supplementary material, which is available to authorized users.

This study fine mapped and validated a QTL on rice chromosome 4 that increases spikelet fertility under high temperature (over 37 °C) at the flowering stage. Climate change has a negative effect on crop production and food security. Understanding the genetic mechanism of heat tolerance and developing heat-tolerant varieties is essential to cope with future global warming. Previously, we reported on a QTL (qHTSF4.1) from an IR64/N22 population responsible for rice spikelet fertility under high-temperature stress at the flowering stage. To further fine map and validate the effect of qHTSF4.1, PCR-based SNP markers were developed and used to genotype BC2F2, BC3F2, BC3F3, and BC5F2 populations from the same cross. The interval of the QTL was narrowed down to about 1.2 Mb; however, further recombination was not identified even with a large BC5F2 population that was subsequently developed and screened. The sequence in the QTL region is highly conserved and a large number of genes in the same gene family were observed to be clustered in the region. The QTL qHTSF4.1 consistently increased spikelet fertility in all of the backcross populations. This was confirmed using 24 rice varieties. Most of the rice varieties with the QTL showed a certain degree of heat tolerance under high-temperature conditions. In a BC5F2 population with clean background of IR64, QTL qHTSF4.1 increased spikelet fertility by about 15 %. It could be an important source for enhancing heat tolerance in rice at the flowering stage. PCR-based SNP markers developed in this study can be used for QTL introgression and for pyramiding with other agronomically important QTLs/genes through marker-assisted selection.

Climate change is increasing night temperature (NT) more than day temperature (DT) in rice-growing areas. Effects of combinations of NT (24−35°C) from microsporogenesis to anthesis at one or more DT (30 or 35°C) at anthesis on rice spikelet fertility, temperature within spikelets, flowering pattern, grain weight per panicle, amylose content and gel consistency were investigated in contrasting rice cultivars under controlled environments. Cultivars differed in spikelet fertility response to high NT, with higher fertility associated with cooler spikelets (P 27°C was estimated to reduce grain weight. Generally, high NT was more damaging to grain weight and selected grain quality traits than high DT, with little or no interaction between them. The critical tolerance and escape traits identified, i.e. spikelet cooling, relatively high spikelet fertility, earlier start and peak time of anthesis and shorter spikelet anthesis duration can aid plant breeding programs targeting resilience in warmer climates.

Cereals such as rice, wheat, maize, and barley account for major proportion of global food grain production. High temperature, drought, and other climate change drivers are predicted to increase in frequency and magnitude, posing serious challenges to sustain global food production under changing climate. These climate change drivers often interact with each other under realistic field conditions resulting in impacts that are notably different compared to individual stress exposure. Till date, there has been no systematic synthesis comparing the impacts of different combinations of high temperature, drought, and elevated CO 2 [eCO 2 ], across cereals. Hence, the major objective of this chapter is to capture the overall agronomic and physiological impact of different combinations of these three factors compared with their independent exposure. High temperature or drought affects almost all growth and developmental phases during crop cycle leading to significant decline in photosynthesis, floral abnormalities, spikelet/kernel sterility, grain yield, and quality losses. Combined high temperature and drought stress can result in additive detrimental effect on growth physiology and productivity. On the other hand, interactive effect of [eCO 2 ] with either high temperature or drought varies with species (C 3 and C 4 ), and also depends on other factors such as phenological stage, intensity and duration of stress, etc. Constraints and available avenues for breeding multiple abiotic stress tolerant cereals, role of modern genomic tools, precision phenotyping, and trait-based breeding program are highlighted. Finally, the chapter summarizes future research direction, in addressing combined stress resilience to ensure sustained global food security under warmer and drier climate.

Extreme temperatures, above and below critical thresholds, lead to heat and cold stress, respectively, in plants – and rice is no exception. Extreme temperatures during flowering and early grain-filling stages result in reproductive failure and reduce grain quality, ultimately resulting in reduced rice yield, quality, and market revenue. Current increases in temperature and predictions of further increasing trends indicate a higher probability of rice production to be affected by heat stress. To overcome extreme temperature stress, developing cold- and heat-tolerant rice varieties using advances in the molecular technology is considered to be both viable and a stable option.

High night temperatures (HNTs) can reduce significantly the global rice (Oryza sativa) yield and quality. A systematic analysis of HNT response at the physiological and molecular levels was performed under field conditions. Contrasting rice accessions, N22 (highly tolerant) and Gharib (susceptible), were evaluated at 22°C (control) and 28°C (HNT). Nitrogen (N) and nonstructural carbohydrate (NSC) translocation from different plant tissues into grains at key developmental stages, and their contribution to yield, grain-filling dynamics and quality aspects, were evaluated. Proteomic profiling of flag leaf and spikelets at 100% flowering and 12 d after flowering was conducted, and their reprogramming patterns were explored. Grain yield reduction in susceptible Gharib was traced back to the significant reduction in N and NSC translocation after flowering, resulting in reduced maximum and mean grain-filling rate, grain weight and grain quality. A combined increase in heat shock proteins (HSPs), Ca signaling proteins and efficient protein modification and repair mechanisms (particularly at the early grain-filling stage) enhanced N22 tolerance for HNT. The increased rate of grain filling and efficient proteomic protection, fueled by better assimilate translocation, overcome HNT tolerance in rice. Temporal and spatial proteome programming alters dynamically between key developmental stages and guides future transgenic and molecular analysis targeted towards crop improvement.

Future increases in global surface temperature threaten those worldwide who depend on rice production for their livelihoods and food security. Past analyses of high-temperature stress on rice production have focused on paddy yield and have failed to account for the detrimental impact of high temperatures on milling quality outcomes, which ultimately determine edible (marketable) rice yield and market value. Using genotype specific rice yield and milling quality data on six common rice varieties from Arkansas, USA, combined with on-site, half-hourly and daily temperature observations, we show a nonlinear effect of high-temperature stress exposure on yield and milling quality. A 1 °C increase in average growing season temperature reduces paddy yield by 6.2%, total milled rice yield by 7.1% to 8.0%, head rice yield by 9.0% to 13.8%, and total milling revenue by 8.1% to 11.0%, across genotypes. Our results indicate that failure to account for changes in milling quality leads to understatement of the impacts of high temperatures on rice production outcomes. These dramatic losses result from reduced paddy yield and increased percentages of chalky and broken kernels, which together decrease the quantity and market value of milled rice. Recently published estimates show paddy yield reductions of up to 10% across the major rice-producing regions of South and Southeast Asia due to rising temperatures. The results of our study suggest that the often-cited 10% figure underestimates the economic implications of climate change for rice producers, thus potentially threatening future food security for global rice producers and consumers.

Wheat, rice, maize, pearl millet, and sorghum provide over half of the world's food calories. To maintain global food security, with the added challenge of climate change, there is an increasing need to exploit existing genetic variability and develop cultivars with superior genetic yield potential and stress adaptation. The opportunity to share knowledge between crops and identify priority traits for future research can be exploited to increase breeding impacts and assist in identifying the genetic loci that control adaptation. A more internationally coordinated approach to crop phenotyping and modeling, combined with effective sharing of knowledge, facilities, and data, will boost the cost effectiveness and facilitate genetic gains of all staple crops, with likely spill over to more neglected crops.

Agricultural production is under increasing pressure by global anthropogenic changes, including rising population, diversion of cereals to biofuels, increased protein demands and climatic extremes. Because of the immediate and dynamic nature of these changes, adaptation measures are urgently needed to ensure both the stability and continued increase of the global food supply. Although potential adaption options often consider regional or sectoral variations of existing risk management (e.g. earlier planting dates, choice of crop), there may be a global-centric strategy for increasing productivity. In spite of the recognition that atmospheric carbon dioxide (CO 2 ) is an essential plant resource that has increased globally by approximately 25 per cent since 1959, efforts to increase the biological conversion of atmospheric CO 2 to stimulate seed yield through crop selection is not generally recognized as an effective adaptation measure. In this review, we challenge that viewpoint through an assessment of existing studies on CO 2 and intraspecific variability to illustrate the potential biological basis for differential plant response among crop lines and demonstrate that while technical hurdles remain, active selection and breeding for CO 2 responsiveness among cereal varieties may provide one of the simplest and direct strategies for increasing global yields and maintaining food security with anthropogenic change.

Due to global climate change, heat and drought stress have an increasing impact on rice ( Oryza sativa L.) yields and become major challenges in agriculture. Severe yield losses were observed when a single stress or a combination of stresses coincide with flowering, but the physiological responses of rice floral organs leading to spikelet sterility are not known. Metabolic and transcriptomic profiling of anthers, pistils before pollination and pollinated pistils was performed to investigate physiological responses determining fertility under heat and combined drought and heat stress using the heat- and drought-tolerant N22 and the heat-sensitive and drought-tolerant cultivar Moroberekan. Different metabolite patterns were observed between floral organs as well as between cultivars under non-stressed and stressed conditions. Several candidate metabolites were differentially accumulated in stressed anthers of N22 compared to Moroberekan under non- stress conditions. More genes were regulated under heat-drought stress than heat stress in anthers of both cultivars with N22 showing much less gene regulation under combined stress in comparison to Moroberekan. The functional class of genes related to stress was over-represented under all stress conditions in both cultivars while fewer bins were over-represented under heat stress compared to combined stress. Combining metabolite and transcriptomic analyses identified sugar metabolism in anthers as crucial for tolerance or susceptibility to stress. In the future, identification of candidate metabolites and genes will be useful for marker assisted selection procedures to breed more stress tolerant crop plants.