Search

Pulse production is decreased when grown on waterlogged soil in rice‐based cropping. This study evaluated four pulse crops—grass pea, field pea, cowpea and lentil—to find out their responses to waterlogging (WL) stress at emergence and vegetative stages. The treatment levels at emergence were drained control, 4‐, 7‐ and 10‐day WL, while in the vegetative stage they were drained control, 6‐, 10‐ and 14‐day WL. In the emergence stage, %emergence was significantly reduced as WL duration increased. After 10‐day WL, emergence was reduced to 65% for grass pea, 30% for field pea, 5% for lentil and 7% for cowpea. At the vegetative stage, in both the WL and recovery phases, the WL treatment reduced plant height, tap root length, shoot and root dry mass compared to those in drained control with a significant difference in crops. In recovery as compared to the WL phase at 14‐day WL, the chlorophyll content was increased 15% in cowpea and 14% in grass pea but decreased in field pea (26%) and lentil (35%). Similarly, in the recovery phase at 14‐day WL, shoot relative growth rates (RGRs) of cowpea, grass pea, field pea and lentil were 20, 66, 10 and 5 mg plant−1 d−1; which were 66%, 70%, 8% and 14% of drained control, respectively. The RGR of root at 14‐day WL was also higher in cowpea and grass pea with the rate of 13.8 and 16 mg−1 plant−1 d−1, respectively; in sharp contrast to a reduction of −4.3 mg−1 plant−1 d−1 in field pea and −3.9 mg−1 plant−1 d−1 for lentil than drained control. Furthermore, the higher number of adventitious roots was found in cowpea (14) and grass (9) pea than in field pea (6) and lentil (4). Comparison between growth stages, grass pea was tolerant to WL in both stages. Cowpea was WL sensitive at emergence, but tolerant to vegetative stage. Field pea was moderately tolerant to emergence but was sensitive at vegetative stage. Lentil was sensitive at WL at both stages. These novel insights will allow the fitting of winter pulses to various cropping systems according to the perceived risk of WL at various growth stages. [ABSTRACT FROM AUTHOR]

Black pepper (Piper nigrum) is a spice commonly used in kitchens throughout the world. Black pepper production is devastated by a range of pathogenic agents, including Phytophthora capsici and Meloidogyne incognita. Many efforts have been directed towards finding black pepper cultivars that are resistant to these pathogens. In this work, a 39‐accession germplasm panel of species in the Piper family collected throughout Vietnam was described. Preliminary tests using P. capsici inoculation onto leaves were carried out to identify potentially resistant accessions. Next, candidate plants were inoculated with P. capsici mycelial suspension and survival rates were assessed 15, 30 and 45 days postinoculation. In addition, Piper plants were challenged with M. incognita by adding larvae/juveniles to growing pots. Resistance to M. incognita was determined by the number of root galls and the percentage of plants with yellow leaves 1, 2 and 4 months after treatment. Piper accessions were also subjected to a 4‐day waterlogged treatment. Two accessions (HUIB_PH30 and HUIB_PD36) demonstrated high levels of resistance to all biological and water stresses. Micromorphological characterizations revealed that the amount of intercellular spaces in the root cortex correlated with the resistance to P. capsici and waterlogging tolerance. Hence, the abundance of intercellular spaces can serve as a guide for further selection of black pepper accessions that are resistant to common diseases and tolerant to waterlogged conditions. [ABSTRACT FROM AUTHOR]

Waterlogging‐sensitive ('ZHC1') and waterlogging‐tolerant ('ZHC2') hot peppers were selected from three years of field investigation. 'ZHC2' could keep growing under waterlogging conditions, its lateral roots were distributed near the water surface, and its stem base grew many adventitious roots and rapidly formed aerenchyma. The chlorophyll content was stable, and the contents of carotenoid and amino acid were significantly greater in 'ZHC2' than in 'ZHC1' under both waterlogging stress and recovery conditions. However, waterlogging stress led to in‐root decay and a significant increase in malondialdehyde content of 'ZHC1'. Using transcriptome analysis, we correlated the functions of many waterlogging‐responsive differentially expressed genes closely with the pathways for reactive oxygen species production, lutein synthesis, auxin signal transduction, and amino acid synthesis, which were consistent with the above growth and physiological data (adventitious root formation and the contents of malondialdehyde, carotenoids and amino acids). Some novel candidate genes related to waterlogging tolerance were also detected. This work provides new insights into waterlogging‐tolerant mechanisms and valuable clues for breeding of waterlogging‐tolerant peppers. [ABSTRACT FROM AUTHOR]

A set of diverse soybean genotypes were evaluated to identify contrasting phenotypes for understanding the genetics of waterlogging and response to the selection of primary and discernable traits for pregermination anaerobic stress tolerance. Agro‐morphological characterization of genotypes was also carried out. Screening and tolerance to waterlogging were based on the ability of genotypes to germinate in excessive stress duration in days. The existence of significant variability in genotypes of soybean suggested the use of systematic selection for improving pregermination anaerobic stress tolerance. The study revealed that waterlogging tolerance was governed by testa colour of genotypes. Our results indicated a significant (P < 0.05) correlation with seed weight, flower, hypocotyl and testa colour under pregermination anaerobic stress. In conclusion, the study points out that testa integrity and delay in germination are required to be used as one of the criteria for indirect selection in breeding for pregermination waterlogging tolerance. [ABSTRACT FROM AUTHOR]

Summary: Tolerance of abiotic stress in woody plants is known to be constrained by biological trade‐offs between different forms of stress, especially shade and drought. However, there is still considerable uncertainty on the relationship between tolerances and the limits on tolerance combinations.Using the most extensive database available on shade, drought, waterlogging and cold tolerance for 799 northern hemisphere woody species, we determined the number of dimensions needed to summarise their tolerance combinations, and the best trade‐off model among those currently available, for description of the interdependence between tolerances.Two principal component analysis (PCA) dimensions summarised stress tolerance combinations. They defined a triangular stress tolerance space (STS). The first STS dimension reflected segregation between drought‐tolerant and waterlogging‐tolerant species. The second reflected shade tolerance, which is independent of the other tolerances. Cold tolerance scaled weakly with both dimensions. Tolerance combinations across the species in the database were limited by boundary‐line trade‐offs.The STS reconciles all major theories about trade‐offs between abiotic stress tolerances, providing a unified trade‐off model and a set of coordinates that can be used to examine how other aspects of plant biology, such as plant functional traits, change within the limits of abiotic stress tolerance. [ABSTRACT FROM AUTHOR]

Models are key tools in our quest to better understand the impacts of soil waterlogging on plant growth and crop production. Here, we reviewed the state of the art of modeling approaches and compared the conceptual design of these models with recent experimental findings. We show that many models adopt an aeration stress (AS) principle where surplus water reduces air‐filled porosity, with implications for root growth. However, subsequent effects of AS within each model vary considerably. In some cases, AS inhibits biomass accumulation (e.g. AquaCrop), altering processes prior to biomass accumulation such as light interception (e.g. APSIM), or photosynthesis and carbohydrate accumulation (e.g. SWAGMAN Destiny). While many models account for stage‐dependent waterlogging effects, few models account for experimentally observed delays in phenology caused by waterlogging. A model intercomparison specifically designed for long‐term waterlogged conditions (APSIM‐Oryza) with models developed for dryland conditions with transient waterlogging would advance our understanding of the current fitness for purpose of exsiting frameworks for simulating transient waterlogging in dryland cropping systems. Of the point‐based dynamic models examined here, APSIM‐Soybean and APSIM‐Oryza simulations most closely matched with the observed data, while GLAM‐WOFOST achieved the highest performance of the spatial‐regional models examined. We conclude that future models should incorporate waterlogging effects on genetic tolerance parameters such as (1) phenology of stress onset, (2) aerenchyma, (3) root hydraulic conductance, (4) nutrient‐use efficiency, and (5) plant ion (e.g. Fe/Mn) tolerance. Incorporating these traits/effects into models, together with a more systematic model intercomparison using consistent initialization data, will significantly improve our understanding of the relative importance of such factors in a systems context, including feedbacks between biological factors, emergent properties, and sensitive variables responsible for yield losses under waterlogging. Key Points: We review the state of the art of approaches used to modeling the impacts of waterlogging on plantsMost models use an aeration stress principle that effects root growth, few models account for phenology delays caused by waterloggingNext generation models should consider new genotypic traits and tolerance (e.g., aerenchyma, ion tolerance, and oxidative stress) [ABSTRACT FROM AUTHOR]

Waterlogging causes oxygen deprivation within plant roots and affects crop growth and yield. In crop wheat (Triticum aestivum), molecular responses to waterlogging are poorly understood. Here, we performed a genome‐wide analysis of group VII ethylene response factor (ERFVII) genes in hexaploid wheat and identified 25 genes, which were induced by waterlogging with diverse manner. Among them, TaERFVII.1 exhibited differential expression patterns between waterlogging‐tolerant wheat Nonglin46 and susceptible wheat Yangmai16 under waterlogging. Constitutive expression of TaERFVII.1 with an MYC‐peptide tag at its N terminus in wheat enhanced tolerance to waterlogging as evidenced by increased grain weight per plant, survival rate, and chlorophyll content of leaves and by increased expression of waterlogging‐responsive genes, while silencing of TaERFVII.1 compromised the expression of waterlogging‐responsive genes. Notably, constitutive expression of the stabilized TaERFVII.1 did not negatively impact both plant development and grain yield under standard conditions. We further demonstrated that constitutive expression of stabilized TaERFVII.1 elevated the transcriptional level of TaSAB18.1, the ortholog of Arabidopsis HRA1 and rice SAB18, consequently reduced the expression of waterlogging‐responsive genes under standard conditions. These results suggest that TaERFVII.1 plays an important role in wheat tolerance to waterlogging, and it could be a candidate for improving crop waterlogging tolerance. Waterlogging severely threatens crop production worldwide. In this study, we identified TaERFVII.1, one of group VII ethylene response factor (ERFVII) genes in hexaploid wheat and provides evidences for its role in enhancing waterlogging tolerance through both overexpression transgene in wheat and gene silencing. Importantly, constitutive expression of the stabilized TaERFVII.1 in wheat does not cause negative impacts on grain yield under standard condition. We further demonstrate that TaSAB18.1, the wheat ortholog of Arabidopsis HRA1 and rice SAB18, reduces transcription of waterlogging‐responsive genes in stabilized TaERFVII.1‐transgenic wheat under standard condition. TaERFVII.1 could be a gene target for improving crop tolerance to waterlogging using gene‐engineering or genome‐editing system. [ABSTRACT FROM AUTHOR]

A radial oxygen loss (ROL) barrier in roots of waterlogging-tolerant plants promotes oxygen movement via aerenchyma to the root tip, and impedes soil phytotoxin entry. The molecular mechanism and genetic regulation of ROL barrier formation are largely unknown. Zea nicaraguensis, a waterlogging-tolerant wild relative of maize ( Zea mays ssp. mays), forms a tight ROL barrier in its roots when waterlogged. We used Z. nicaraguensis chromosome segment introgression lines (ILs) in maize (inbred line Mi29) to elucidate the chromosomal region involved in regulating root ROL barrier formation. A segment of the short-arm of chromosome 3 of Z. nicaraguensis conferred ROL barrier formation in the genetic background of maize. This chromosome segment also decreased apoplastic solute permeability across the hypodermis/exodermis. However, the IL and maize were similar for suberin staining in the hypodermis/exodermis at 40 mm and further behind the root tip. Z. nicaraguensis contained suberin in the hypodermis/exodermis at 20 mm and lignin at the epidermis. The IL with ROL barrier, however, did not contain lignin in the epidermis. Discovery of the Z. nicaraguensis chromosomal region responsible for root ROL barrier formation has improved knowledge of this trait and is an important step towards improvement of waterlogging tolerance in maize. [ABSTRACT FROM AUTHOR]

Aims According to traditional ecophysiological theories stress tolerance of plants is predominately determined by universal physiochemical constraints. Plant acclimation to environmental stress therefore compromises plant performance under a different stress, hindering successful toleration of several abiotic stress factors simultaneously. Yet recent studies have shown that these trade-offs are less exclusive than postulated so far, leaving more wiggle room for gaining polytolerance through adaptations. We tested whether polytolerance to shade and drought depends on cold and waterlogging tolerances - hypothesizing that polytolerance patterns in different species groups (angiosperms versus gymnosperms; deciduous versus evergreen; species originating from North America, Europe and East Asia) depend on the length of the vegetation period and species dormancy through limiting the duration of favourable growing season. Location Northern Hemisphere. Methods Our study analysed four main abiotic stress factors - shade, drought, cold and waterlogging stress - for 806 Northern Hemisphere woody species using cross-calibrated tolerance rankings. The importance of trade-offs among species ecological potentials was evaluated using species-specific estimates of polytolerance to chosen factors. Results We found that both cold and waterlogging tolerance are negatively related to species capabilities of simultaneously tolerating low-light and low-water conditions. While this pattern was different in angiosperms and gymnosperms, species region of origin and leaf type had no effect on this relationship. Main conclusions Our results demonstrate that adaptation to different abiotic stress factors in woody plants is highly complex. The length of the vegetation period and dormancy are the key factors explaining why woody plants are less capable of tolerating both shade and drought in habitats where vegetation period is relatively short and the water table high. While dormancy enables angiosperms to more successfully face additional stress factors besides shade and drought, gymnosperms have lower polytolerance, but can better tolerate of shade and drought when other environmental factors are favourable. [ABSTRACT FROM AUTHOR]

Vast agricultural areas are affected by flooding, causing up to 80% yield reduction and resulting in multibillion dollar losses. Up to now, the focus of plant breeders was predominantly on detrimental effects of anoxia, while other (potentially equally important) traits were essentially neglected; one of these is soil elemental toxicity. Excess water triggers a progressive decrease in soil redox potential, thus increasing the concentration of Mn2+ that can be toxic to plants if above a specific threshold. This work aimed to quantify the relative contribution of Mn2+ toxicity to waterlogging stress tolerance, using barley as a case study. Twenty barley ( Hordeum vulgare) genotypes contrasting in waterlogging stress tolerance were studied for their ability to cope with toxic (1 m m) amounts of Mn2+ in the root rhizosphere. Under Mn2+ toxicity, chlorophyll content of most waterlogging-tolerant genotypes (TX9425, Yerong, CPI-71284-48 and CM72) remained above 60% of the control value, whereas sensitive genotypes (Franklin and Naso Nijo) had 35% less chlorophyll than 35% of controls. Manganese concentration in leaves was not related to visual Mn2+ toxicity symptoms, suggesting that various Mn2+ tolerance mechanisms might operate in different tolerant genotypes, i.e. avoidance versus tissue tolerance. The overall significant (r = 0.60) correlation between tolerance to Mn2+ toxicity and waterlogging in barley suggests that plant breeding for tolerance to waterlogging traits may be advanced by targeting mechanisms conferring tolerance to Mn2+ toxicity, at least in this species. [ABSTRACT FROM AUTHOR]

• The subapical regions of wetland plant roots can develop a barrier to radial O2 loss (ROL), but barrier resistance has rarely been quantified in terms of its O2 diffusivity. • Barrier resistance in adventitious roots of the waterlogging-tolerant Hordeum marinum was assessed from measurements of ROL using cylindrical platinum electrodes while either varying shoot O2 partial pressures or cooling the rooting medium. Anatomical features were examined using fluorescence microscopy. • When grown in stagnant agar nutrient solution, a barrier to ROL was induced over the basal half of 100–120-mm-long roots. Autofluorescence in hypodermal cell walls indicated that putative suberin deposition was coincident with barrier expression. Root cooling revealed a significant respiratory component in barrier resistance. Eliminating the respiration effect by manipulating shoot O2 partial pressures revealed an O2 diffusivity for the barrier of 5.96 × 10−7 cm2 s−1, 96% less than that at the apex, which was ≥ 1.59 × 10−5 cm2 s−1. • It is concluded that the ROL barrier is a manifestation of two components acting synergistically: a physical resistance caused principally by secondary cell-wall deposits in the outer hypodermal layer; and respiratory activity in the hypodermal/epidermal layers; with physical resistance being the dominant component. [ABSTRACT FROM AUTHOR]

Lack of information on ecological characteristics of species across different continents hinders development of general world-scale quantitative vegetation dynamic models. We constructed common scales of shade, drought, and waterlogging tolerance for 806 North American, European/West Asian, and East Asian temperate shrubs and trees representing about 40% of the extant natural Northern Hemisphere species pool. These scales were used to test the hypotheses that shade tolerance is negatively related to drought and waterlogging tolerances, and that these correlations vary among continents and plant functional types. We observed significant negative correlations among shade and drought tolerance rankings for all data pooled, and separately for every continent and plant functional type, except for evergreen angiosperms. Another significant trade-off was found for drought and waterlogging tolerance for all continents, and for evergreen and deciduous angiosperms, but not for gymnosperms. For all data pooled, for Europe and East Asia, and for evergreen and deciduous angiosperms, shade tolerance was also negatively associated with waterlogging tolerance. Quantile regressions revealed that the negative relationship between shade and drought tolerance was significant for species growing in deep to moderate shade and that the negative relationship between shade and waterlogging tolerance was significant for species growing in moderate shade to high light, explaining why all relationships between different tolerances were negative according to general regression analyses. Phylogenetic signal in the tolerance to any one of the three environmental factors studied was significant but low, with only 21–24% of cladogram nodes exhibiting significant conservatism. The inverse relationships between different tolerances were significant in phylogenetically independent analyses both for the overall pool of species and for two multispecies genera (Pinus and Quercus) for which reliable molecular phylogenies were available. Only 2.6–10.3% of the species were relatively tolerant to two environmental stresses simultaneously (tolerance value ≥3), and only three species were tolerant to all three stresses, supporting the existence of functional trade-offs in adjusting to multiple environmental limitations. These trade-offs represent a constraint for niche differentiation, reducing the diversity of plant responses to the many combinations of irradiance and water supply that are found in natural ecosystems. [ABSTRACT FROM AUTHOR]

Summary: Geum rivale L. and G. urbanum L. were grown in drained, continuously flooded or transiently flooded compost for 21 weeks. Leaf and root material harvested after this time was analyzed for Fe, Mn, Ca and P. Mn and Fe concentrations in roots and leaves of both species were increased by flooding. Higher Fe concentrations accumulated in the roots, while Mn was present in roughly equal concentrations in both roots and leaves. Leaf Ca concentration of both species was higher than that of roots. Although Ca concentrations were significantly higher in G. rivale than in G. urbanum, there were no readily interpretable effects of waterlogging. P concentration was decreased in leaves and increased in roots of flooded G. urbanum, although there was much less effect of flooding on P concentration in G. rivale. Fe may be precipitated by phosphate in G. urbanum roots, but this may lead to P deficiency in shoots and roots, resulting in poor growth of this species in waterlogged soil. A different mechanism of Fe immobilization is likely to occur in G. rivale, which does not result in phosphorus deficiency. [ABSTRACT FROM AUTHOR]