Waterlogging Tolerance Research Articles

Crop traits enabling yield gains under more frequent extreme climatic events

Climate change (CC) in central China will change seasonal patterns of agricultural production through increasingly frequent extreme climatic events (ECEs). Breeding climate-resilient wheat (Triticum aestivum L.) genotypes may mitigate adverse effects of ECEs on crop productivity. To reveal crop traits conducive to long-term yield improvement in the target population of environments, we created 8,192 virtual genotypes with contrasting but realistic ranges of phenology, productivity and waterlogging tolerance. Using these virtual genotypes, we conducted a genotype (G) by environment (E) by management (M) factorial analysis (G×E×M) using locations distributed across the entire cereal cropping zone in mid-China. The G×E×M invoked locally-specific sowing dates under future climates that were premised on shared socioeconomic pathways SSP5-8.5, with a time horizon centred on 2080. Across the simulated adaptation landscape, productivity was primarily driven by yield components and phenology (average grain yield increase of 6-69% across sites with optimal combinations of these traits). When incident solar radiation was not limiting carbon assimilation, ideotypes with higher grain yields were characterised by earlier flowering, higher radiation-use efficiency and larger maximum kernel size. At sites with limited solar radiation, crops required longer growing periods to realise genetic yield potential, although higher radiation-use efficiency and larger maximum kernel size were again prospective traits enabling higher rates of yield gains. By 2080, extreme waterlogging stress in some regions of mid-China will impact substantially on productivity, with yield penalties of up to 1,010 kg ha−1. Ideotypes with optimal G×M could mitigate yield penalty caused by waterlogging by up to 15% under future climates. These results help distil promising crop trait by best management practice combinations that enable higher yields and robust adaptation to future climates and more frequent extreme climatic events, including flash flooding and soil waterlogging.

Improving phenotyping in winter barley cultivars towards waterlogging tolerance by combining field trials under natural conditions with controlled growth condition experiments

Additional rainfall in Northern Europe due to global climate change is increasing the incidences of field flooding. Flooding causes hypoxic stress that results in a reduced capacity for photosynthesis, reduction in nutrient availability and uptake, increased production of toxic metabolites by anaerobic bacteria in the soil, and ultimately yield losses and crop death. To overcome hypoxic environmental conditions, new cultivars need to be bred and tested for waterlogging tolerance. We scored 403 winter barley cultivars from the ‘Association Genetics of UK Elite Barley’ (AGOUEB) population, taking advantage of the phenotypic changes associated with hypoxic stress. This enabled us to identify an initial set of waterlogging sensitive and tolerant cultivars. Comparative analysis of a subset of 65 cultivars exposed to waterlogging stress under field and growth cabinet environments showed variability in scores due to varying sensitivity to waterlogging over multi-season field trials. In field trials, we observed waterlogging damage resulting in reductions in biomass, grain yield and crop height. However, the effects varied between seasons and the severity of waterlogging due to differences in the topography of the field and the amount of rainfall. To overcome the seasonal variations in environmental conditions in multi-season field trials, we developed in parallel, an enhanced phenotyping method by complementing field experiments with phenotyping under controlled growth conditions. The phenotyping scoring method allows for the grouping of cultivars by sensitivity and tolerance to waterlogging, with limited variance between cultivars scored in the field and controlled conditions. Together, these two complementary approaches maximise the data available to breeders, allowing for the reliable selection of more tolerant cultivars able to grow under flooding conditions.

Screening of cowpea (Vigna unguiculata (L.) Walp.) genotypes for waterlogging tolerance using morpho-physiological traits at early growth stage

The majority of cowpea (Vigna unguiculata (L.) Walp.) produced in the U.S. is planted shortly after the summer rains and subsequently depends on rain or artificial irrigation. Therefore, excessive precipitation and poor soil drainage will cause cowpea plants to suffer temporary waterlogging, reducing the submerged tissue's oxygen level. Although cowpea is sensitive to waterlogging, excessive moisture can induce several morpho-physiological changes with adverse impacts on yield in its early stages of development. The current study subjected 30 cowpea genotypes to 10-days of waterlogging at the seedling stage under a controlled environment. The dynamic changes of 24 morpho-physiological parameters under waterlogging and optimal water conditions were analyzed to understand cowpea's response to waterlogging. Significant waterlogging treatment, cowpea genotypes, and their interactions (P < 0.001) were observed for most of the measured parameters. The results indicated that plant height (PH), leaf area (LA), fresh (FW) and dry weight (DW) of cowpea genotypes were significantly decreased under waterlogging compared to the control treatments. Similar results were obtained for net photosynthesis (Pn), stomatal conductance (gs), intercellular CO2 concentration (Ci), and transpiration rate (E). However, the water use efficiency (WUE) and adventitious roots (ARs) increased linearly under waterlogging conditions. Waterlogging also declined chlorophyll fluorescence parameters except non-photochemical quenching (qN), which increased with excess soil moisture. In addition, waterlogging tolerance coefficient (WTC) and multivariate analysis (MCA) methods were used to characterize cowpea genotypes for waterlogging tolerance. Accordingly, the cowpea genotype Dagupan Pangasinan, UCR 369, and Negro were classified as waterlogging tolerant, while EpicSelect.4 and ICARDA 140071, as the most waterlogging sensitive. The cowpea genotypes and morpho-physiological traits determined from this study may be useful for genetic engineering and breeding programs that integrate cowpea waterlogging tolerance.

Breeding for higher yield, early maturity, wider adaptability and waterlogging tolerance in soybean (Glycine max L.): A case study

Breeding for higher yield and wider adaptability are major objectives of soybean crop improvement. In the present study, 68 advanced breeding lines along with seven best checks were evaluated for yield and attributing traits by following group balanced block design. Three blocks were constituted based on the maturity duration of the breeding lines. High genetic variability for the twelve quantitative traits was found within and across the three blocks. Several genotypes were found to outperform check varieties for yield and attributing traits. During the same crop season, one of the promising entries, NRC 128,was evaluated across seven locations for its wider adaptability and it has shown stable performance in Northern plain Zone with > 20% higher yield superiority over best check PS 1347. However, it produced 9.8% yield superiority over best check in Eastern Zone. Screening for waterlogging tolerance under artificial conditions revealed that NRC 128 was on par with the tolerant variety JS 97–52. Based on the yield superiority, wider adaptability and waterlogging tolerance, NRC 128 was released and notified by Central Varietal Release Committee (CVRC) of India, for its cultivation across Eastern and Northern Plain Zones of India.

6-Benzyladenine increasing subsequent waterlogging-induced waterlogging tolerance of summer maize by increasing hormone signal transduction.

Summer maize is frequently subjected to waterlogging damage because of increased and variable rainfall during the growing season. The application of 6-benzyladenine (6-BA) can effectively mitigate the waterlogging effects on plant growth and increase the grain yield of waterlogged summer maize. However, the mechanisms underlying this process and the involvement of 6-BA in relevant signal transduction pathways remain unclear. In this study, we explored the effects of 6-BA on waterlogged summer maize using a phosphoproteomic technique to better understand the mechanism by which summer maize growth improves following waterlogging. Application of 6-BA inhibited the waterlogging-induced increase in abscisic acid (ABA) content and increased the phosphorylation levels of proteins involved in ABA signaling; accordingly, stomatal responsiveness to exogenous ABA increased. In addition, the application of 6-BA had a long-term effect on signal transduction pathways and contributed to rapid responses to subsequent stresses. Plants primed with 6-BA accumulated more ethylene and jasmonic acid in response to subsequent waterlogging; accordingly, leaf SPAD, antioxidase activity, and root traits improved by 6-BA priming. These results suggest that the effects of 6-BA on hormone signal transduction pathways are anamnestic, which enables plants to show faster or stronger defense responses to stress.

Transient Waterlogging Events Impair Shoot and Root Physiology and Reduce Grain Yield of Durum Wheat Cultivars.

Durum wheat (Triticum turgidum L. subsp. durum (Desf.) Husn) is a staple crop of the Mediterranean countries, where more frequent waterlogging events are predicted due to climate change. However, few investigations have been conducted on the physiological and agronomic responses of this crop to waterlogging. The present study provides a comprehensive evaluation of the effects of two waterlogging durations (i.e., 14 and 35 days) on two durum wheat cultivars (i.e., Svevo and Emilio Lepido). An integrated analysis of an array of physiological, biochemical, biometric, and yield parameters was performed at the end of the waterlogging events, during recovery, and at physiological maturity. Results established that effects on durum wheat varied depending on waterlogging duration. This stress imposed at tillering impaired photosynthetic activity of leaves and determined oxidative injury of the roots. The physiological damages could not be fully recovered, subsequently slowing down tiller formation and crop growth, and depressing the final grain yield. Furthermore, differences in waterlogging tolerance between cultivars were discovered. Our results demonstrate that in durum wheat, the energy maintenance, the cytosolic ion homeostasis, and the ROS control and detoxification can be useful physiological and biochemical parameters to consider for the waterlogging tolerance of genotypes, with regard to sustaining biomass production and grain yield.

Comparative Proteomic Analysis of Grapevine Rootstock in Response to Waterlogging Stress.

Waterlogging severely affects global agricultural production. Clarifying the regulatory mechanism of grapevine in response to waterlogging stress will help to improve the waterlogging tolerance of grapevine. In the present study, the physiological and proteomic responses of SO4 grapevine rootstock to different waterlogging tolerances were comparatively assayed. The results showed that the activities of SOD and POD first increased and then decreased, while the change trend of CAT and APX activities was the opposite. In addition, the MDA and H2O2 contents increased after waterlogging treatment, but the chlorophyll a and chlorophyll b contents decreased. A total of 5,578 grapevine proteins were identified by the use of the tandem mass tag (TMT) labeling technique. Among them, 214 (103 and 111 whose expression was upregulated and downregulated, respectively), 314 (129 and 185 whose expression was upregulated and downregulated, respectively), and 529 (248 and 281 whose expression was upregulated and downregulated, respectively) differentially expressed proteins (DEPs) were identified in T0d vs. T10d, T10d vs. T20d, and T0d vs. T20d comparison groups, respectively. Enrichment analysis showed that these DEPs were mainly involved in glutathione metabolism, carbon fixation, amino sugar and nucleotide sugar metabolism, biosynthesis of amino acids, photosynthesis, carbon metabolism, starch, and sucrose metabolism, galactose metabolism, protein processing and ribosomes. To further verify the proteomic data, the expression of corresponding genes that encode eight DEPs was confirmed by quantitative reverse transcriptase-polymerase chain reaction (qRT-PCR). The results of this study presented an important step toward understanding the resistance mechanisms of grapevine in response to waterlogging stress at the proteome level.

Assessing the Response of Diverse Sesame Genotypes to Waterlogging Durations at Different Plant Growth Stages.

Sesame is sensitive to waterlogging, and its growth is devastatingly impacted under excess moisture conditions. Thus, waterlogging tolerance is crucial to alleviate yield constraints, particularly under expected climate change. In this study, 119 diverse sesame genotypes were screened for their tolerance to 12, 24, 48, and 72 h of waterlogging relative to non-waterlogged conditions. All plants died under 72 h of waterlogging, while 13.45%, 31.93%, and 45.38% of genotypes survived at 48, 24, and 12 h, respectively. Based on the seedling parameters and waterlogging tolerance coefficients, genotypes BD-7008 and BD-6985 exhibited the highest tolerance to waterlogging, while BD-6996 and JP-01811 were the most sensitive ones. The responses of these four genotypes to waterlogged conditions were assessed at different plant growth stages—30, 40, and 50 days after sowing (DAS)—versus normal conditions. Waterlogging, particularly when it occurred within 30 DAS, destructively affected the physiological and morphological characteristics, which was reflected in the growth and yield attributes. Genotype BD-7008, followed by BD-6985, exhibited the highest chlorophyll and proline contents as well as enzymatic antioxidant activities, including superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT). These biochemical and physiological adjustments ameliorated the adverse effects of waterlogging, resulting in higher yields for both genotypes. Conversely, JP-01811 presented the lowest chlorophyll and proline contents as well as enzymatic antioxidant activities, resulting in the poorest growth and seed yield.

Crosstalk between H2 S and NO: an emerging signalling pathway during waterlogging stress in legume crops.

In legumes, waterlogging is a major detrimental factor leading to huge yield losses. Generally, legumes lack tolerance to submergence, and conventional breeding to develop tolerant varieties are limited due to the lack of tolerant germplasm and potential target genes. Moreover, our understanding of the various signalling cascades, their interactions and key pathways induced during waterlogging is limited. Here, we focus on the role of two important plant signalling molecules, viz. hydrogen sulphide (H2 S) and nitric oxide (NO), during waterlogging stress in legumes. Plants and soil microbes produce these signalling molecules both endogenously and exogenously under various stresses, including waterlogging. NO and H2 S are known to regulate key physiological pathways, such as stomatal closure, leaf senescence and regulation of numerous stress signalling pathways, while NO plays a pivotal role in adventitious root formation during waterlogging. The crosstalk between H2 S and NO is synergistic because of the resemblance of their physiological effects and proteomic functions, which mainly operate through cysteine-dependent post-translational modifications via S-nitrosation and persulfidation. Such knowledge has provided novel platforms for researchers to unravel the complexity associated with H2 S-NO signalling and interactions with plant stress hormones. This review provides an overall summary on H2 S and NO, including biosynthesis, biological importance, crosstalk, transporter regulation as well as understanding their role during waterlogging using 'multi-omics' approach. Understanding H2 S and NO signalling will help in deciphering the metabolic interactions and identifying key regulatory genes that could be used for developing waterlogging tolerance in legumes.

Response of morphological and biochemical traits of maize genotypes under waterlogging stress

Maize (Zea mays L.) is one of the most important cereal crops cultivated around the world. Waterlogging stress is a major production constraint of maize production in rain-fed agricultural systems. The main objective of this experiment was to investigate the effect of continuous waterlogging on morphological and biochemical traits of maize genotypes at the vegetative stage. Ten maize genotypes were treated under no waterlogging (control) and continuous waterlogging of five centimeters depth for 10 days. The treatments were applied to the plants at their 45 days of age. Visual leaf injury scores from Leaf 4 (youngest leaf is the reference point) to Leaf 7 separated tolerant and susceptible genotypes. Waterlogging stress significantly reduced the total number of live leaves and chlorophyll content in leaf tissues in susceptible genotypes. The anatomical study revealed that tolerant maize genotypes produce a large number of aerenchyma cells under waterlogging stress compared to susceptible genotypes. The enzymatic activities of ascorbate peroxidase (APX) and peroxidase (POD) exhibited a greater increase in tolerant genotypes than susceptible genotypes whereas the contents of reactive oxygen species (H2O2) greatly increased in susceptible genotypes than tolerant genotypes under waterlogging stress compared to control. Principal component 2 (PC2) indicated that increasing plant height in the genotypes BHM-14, BHM-13 and BHM-9 was associated with waterlogging tolerance. The findings of this experiment will add value to maize breeding to screen out maize genotypes for waterlogging stress tolerance.

Waterlogging tolerance evaluation of fifteen poplar clones cultivated in the Jianghan Plain of China

To provide references for poplar cultivation in waterlogged prone area of Jianghan Plain of China, the waterlogging tolerance of 15 poplar clones widely cultivated in these areas were evaluated based on their responses to 45-day waterlogging stress followed by 15-day drainage recovery in morphology, growth, biomass accumulation, leaf gas exchange and chlorophyll fluorescence parameters. The results showed that the normal watered seedlings (CK) of the 15 clones grew vigorously during the experiment, and no defoliation and death occurred. For the seedlings under waterlogging treatment (water 10 cm above the soil surface), its morphology changed markedly, including slowing growth, chlorosis and abscission of leaves, development of hypertrophied lenticels and adventitious roots etc. Waterlogging stress significantly inhibited the seedling growth of height and ground diameter, biomass accumulation, as well as leaf gas exchange and chlorophyll fluorescence parameters of the 15 clones with varying degrees. The net photosynthetic rate (Pn), stomatal conductance (Gs), transpiration rate (Tr), intercellular CO2 concentration/ environmental CO2 concentration (Ci/Ca), variable fluorescence (Fv), variable fluorescence/ initial fluorescence (Fv/Fo) and PS Ⅱ primary light energy conversion efficiency (Fv/Fm) decreased gradually with the prolonged waterlogging, and reached their bottom on day 45. During the terminal recovery stage, the leaf gas exchange and chlorophyll fluorescence parameters of the most clones increased, but their recovery abilities were significantly different. At the end of the experiment, the highest survival rates (100%) were observed in DHY, HS-1, HS-2, I-72, I-69, I-63 and NL-895, and the lowest (zero) occurred in XYY. Survival rates of the other clones ranged from 33.33% to 83.33%. Both results of cluster analysis and membership function analysis showed that HS-1, I-69, DHY, NL-895 and HS-2 had the strongest waterlogging tolerance, XYY and HBY were the worst, and the other clones were moderate. These results would provide guidance not only for the selection of cultivated varieties in Jianghan Plain, but also for the selection of hybrid parents for waterlogging resistance breeding.

Genome-Wide Association Study of Waterlogging Tolerance in Barley (Hordeum vulgare L.) Under Controlled Field Conditions.

Waterlogging is one of the main abiotic stresses severely reducing barley grain yield. Barley breeding programs focusing on waterlogging tolerance require an understanding of genetic loci and alleles in the current germplasm. In this study, 247 worldwide spring barley genotypes grown under controlled field conditions were genotyped with 35,926 SNPs with minor allele frequency (MAF) > 0.05. Significant phenotypic variation in each trait, including biomass, spikes per plant, grains per plant, kernel weight per plant, plant height and chlorophyll content, was observed. A genome-wide association study (GWAS) based on linkage disequilibrium (LD) for waterlogging tolerance was conducted. Population structure analysis divided the population into three subgroups. A mixed linkage model using both population structure and kinship matrix (Q+K) was performed. We identified 17 genomic regions containing 51 significant waterlogging-tolerance-associated markers for waterlogging tolerance response, accounting for 5.8–11.5% of the phenotypic variation, with a majority of them localized on chromosomes 1H, 2H, 4H, and 5H. Six novel QTL were identified and eight potential candidate genes mediating responses to abiotic stresses were located at QTL associated with waterlogging tolerance. To our awareness, this is the first GWAS for waterlogging tolerance in a worldwide barley collection under controlled field conditions. The marker-trait associations could be used in the marker-assisted selection of waterlogging tolerance and will facilitate barley breeding.

Study on Screening of Waterlogging Tolerance Germplasm Resources of Zanthoxylum bungeanum

In order to screen out strong waterlogging tolerance germplasm resources of Zanthoxylum bungeanum, the growth and waterlogging damage of six Z. bungeanum germplasm materials selected by Sichuan academy of botanical engineering in the early stage were comprehensively evaluated through artificial flooding experiment. The results showed that under waterlogging stress, Chuanzhi-3 still maintained a large stress index of plant height and basal diameter growth, and the waterlogging symptoms appeared only after waterlogging stress for 66 h, with a waterlogging index of only 5.56%, and after waterlogging stress for 96 h, the waterlogging index was 55.56%. The average waterlogging index of each treatment was only 9.63%. The waterlogging symptoms of Chuanzhi-3 were much lighter than other materials, and the waterlogging tolerance was the strongest.

Response of Mungbean (cvs. Celera II-AU and Jade-AU) and Blackgram (cv. Onyx-AU) to Transient Waterlogging.

Mungbean [Vigna radiata (L.) Wilczek] and blackgram [Vigna mungo (L.) Hepper] are important crops for smallholder farmers in tropical and subtropical regions. Production of both crops is affected by unexpected and increasingly frequent extreme precipitation events, which result in transient soil waterlogging. This study aimed to compare the waterlogging tolerance of mungbean and blackgram genotypes under the varying duration of waterlogging stress at germination and seedling stages. We evaluated the responses to different durations of transient waterlogging in a sandy clay loam under temperature-controlled glasshouse conditions. Waterlogging durations were 0, 1, 2, 3, 4, 5, 6, 7, and 8 days during germination and 0, 2, 4, 8, and 16 days during the seedling stage. We used two mungbean genotypes (green testa), Celera II-AU (small-seeded), and Jade-AU (large-seeded), contrasting in seed size and hypocotyl pigmentation, and a blackgram genotype (black testa), Onyx-AU. Waterlogging reduced soil redox potential, delayed or even prevented germination, decreased seedling establishment, and affected shoot and root development. In the seedlings waterlogged (WL) at 15 days after sowing (DAS), adventitious root formation and crown nodulation varied between the genotypes, and 16 days of waterlogging substantially reduced growth but did not result in plant death. Plants in soil with waterlogging for 8–16 days followed by drainage and sampling at 39 DAS had reduced shoot and root dry mass by 60–65% in mungbean and 40% in blackgram compared with continuously drained controls, due at least in part to fewer lateral roots. Soil plant analysis development (SPAD) chlorophyll content was also reduced. Onyx-AU, a blackgram genotype, was more tolerant to transient waterlogging than Jade-AU and Celera II-AU in both growth stages. Of the two mungbean genotypes, Celera II-AU had a greater seedling establishment than Jade-AU post waterlogging imposed at sowing. In contrast, Jade-AU had more plant biomass and greater recovery growth than Celera II-AU after waterlogging and recovery during the seedling stage. Both species were delayed in emergence in response to the shorter periods of transient waterlogging at germination, and with the longer waterlogging germination and emergence failed, whereas at the seedling stage both showed adaptation by the formation of adventitious roots.

Quantitative Proteomics and Relative Enzymatic Activities Reveal Different Mechanisms in Two Peanut Cultivars (Arachis hypogaea L.) Under Waterlogging Conditions.

Peanut is an important oil and economic crop in China. The rainy season (April–June) in the downstream Yangtze River in China always leads to waterlogging, which seriously affects plant growth and development. Therefore, understanding the metabolic mechanisms under waterlogging stress is important for future waterlogging tolerance breeding in peanut. In this study, waterlogging treatment was carried out in two different peanut cultivars [Zhonghua 4 (ZH4) and Xianghua08 (XH08)] with different waterlogging tolerance. The data-independent acquisition (DIA) technique was used to quantitatively identify the differentially accumulated proteins (DAPs) between two different cultivars. Meanwhile, the functions of DAPs were predicted, and the interactions between the hub DAPs were analyzed. As a result, a total of 6,441 DAPs were identified in ZH4 and its control, of which 49 and 88 DAPs were upregulated and downregulated under waterlogging stress, respectively, while in XH08, a total of 6,285 DAPs were identified, including 123 upregulated and 114 downregulated proteins, respectively. The hub DAPs unique to the waterlogging-tolerant cultivar XH08 were related to malate metabolism and synthesis, and the utilization of the glyoxylic acid cycle, such as L-lactate dehydrogenase, NAD+-dependent malic enzyme, aspartate aminotransferase, and glutamate dehydrogenase. In agreement with the DIA results, the alcohol dehydrogenase and malate dehydrogenase activities in XH08 were more active than ZH4 under waterlogging stress, and lactate dehydrogenase activity in XH08 was prolonged, suggesting that XH08 could better tolerate waterlogging stress by using various carbon sources to obtain energy, such as enhancing the activity of anaerobic respiration enzymes, catalyzing malate metabolism and the glyoxylic acid cycle, and thus alleviating the accumulation of toxic substances. This study provides insight into the mechanisms in response to waterlogging stress in peanuts and lays a foundation for future molecular breeding targeting in the improvement of peanut waterlogging tolerance, especially in rainy area, and will enhance the sustainable development in the entire peanut industry.

Tolerance of four grain legume species to waterlogging, hypoxia and anoxia at germination and recovery.

Legume seeds, when relay sown following rice, may suffer from soil waterlogging and the associated hypoxia or even anoxia. This study evaluated the tolerance of grain legume species, grass pea (three genotypes), lentil (two genotypes), faba bean (two genotypes) and field pea (one genotype), to soil waterlogging in a glasshouse, to anoxia and hypoxia in temperature-controlled room at germination and seedling stages. Changes in oxygen in the surface layers of soil, with time after waterlogging, were measured by microelectrode profiling. The soil profiling showed that soil oxygen declined and then stabilized by the fourth day after waterlogging and oxygen was not detected at 8 mm below the soil surface. Germination of seeds under waterlogging for up to 12 days and seedling survival after the soil was drained for up to 36 days were measured in pot experiments. Seed germination and/or survival in anoxia (N2-flushed solutions) and hypoxia (1.0 and 2.5 kPa oxygen) were evaluated, and so were post-anoxia or post-hypoxia recoveries, all in comparison with aerated controls. Lentil had higher seedling emergence (55 %) than the other species during soil waterlogging. However, lentil had lower seedling survival (9 %) than grass pea (28 %) during recovery following soil drainage. Grass pea seeds were more tolerant of anoxia and of hypoxia than the seeds of the three other species. In conclusion, grass pea, with higher percent germination and seedling survival during recovery, is more tolerant to waterlogging and subsequent soil drainage than the three other grain legume species. Grass pea was also more tolerant of hypoxia and of anoxia at the seed germination stage. These findings demonstrate the superior waterlogging tolerance of grass pea in relay sowing, as compared with the other grain legumes.

Waterlogging-Stress-Responsive LncRNAs, Their Regulatory Relationships with miRNAs and Target Genes in Cucumber (Cucumis sativus L.)

Low oxygen level is a phenomenon often occurring during the cucumber cultivation period. Genes involved in adaptations to stress can be regulated by non-coding RNA. The aim was the identification of long non-coding RNAs (lncRNAs) involved in the response to long-term waterlogging stress in two cucumber haploid lines, i.e., DH2 (waterlogging tolerant—WL-T) and DH4 (waterlogging sensitive—WL-S). Plants, at the juvenile stage, were waterlogged for 7 days (non-primed, 1xH), and after a 14-day recovery period, plants were stressed again for another 7 days (primed, 2xH). Roots were collected for high-throughput RNA sequencing. Implementation of the bioinformatic pipeline made it possible to determine specific lncRNAs for non-primed and primed plants of both accessions, highlighting differential responses to hypoxia stress. In total, 3738 lncRNA molecules were identified. The highest number (1476) of unique lncRNAs was determined for non-primed WL-S plants. Seventy-one lncRNAs were depicted as potentially being involved in acquiring tolerance to hypoxia in cucumber. Understanding the mechanism of gene regulation under long-term waterlogging by lncRNAs and their interactions with miRNAs provides sufficient information in terms of adaptation to the oxygen deprivation in cucumber. To the best of our knowledge, this is the first report concerning the role of lncRNAs in the regulation of long-term waterlogging tolerance by priming application in cucumber.

Opportunities for Improving Waterlogging Tolerance in Cereal Crops—Physiological Traits and Genetic Mechanisms

Waterlogging occurs when soil is saturated with water, leading to anaerobic conditions in the root zone of plants. Climate change is increasing the frequency of waterlogging events, resulting in considerable crop losses. Plants respond to waterlogging stress by adventitious root growth, aerenchyma formation, energy metabolism, and phytohormone signalling. Genotypes differ in biomass reduction, photosynthesis rate, adventitious roots development, and aerenchyma formation in response to waterlogging. We reviewed the detrimental effects of waterlogging on physiological and genetic mechanisms in four major cereal crops (rice, maize, wheat, and barley). The review covers current knowledge on waterlogging tolerance mechanism, genes, and quantitative trait loci (QTL) associated with waterlogging tolerance-related traits, the conventional and modern breeding methods used in developing waterlogging tolerant germplasm. Lastly, we describe candidate genes controlling waterlogging tolerance identified in model plants Arabidopsis and rice to identify homologous genes in the less waterlogging-tolerant maize, wheat, and barley.

Nitrate nutrition increases foliar levels of nitric oxide and waterlogging tolerance in soybean

Nitrate nutrition increases foliar levels of nitric oxide and waterlogging tolerance in soybean

Novel functions of the root barrier to radial oxygen loss - radial diffusion resistance to H2 and water vapour.

The root barrier to radial O2 loss (ROL) is a trait enabling waterlogging tolerance of plants. The ROL barrier restricts O2 diffusion to the anoxic soil so that O2 is retained inside root tissues. We hypothesised that the ROL barrier can also restrict radial diffusion of other gases (H2 and water vapour) in rice roots with a barrier to ROL. We used O2 and H2 microsensors to measure ROL and permeability of rice roots, and gravimetric measurements to assess the influence of the ROL barrier on radial water loss (RWL). The ROL barrier greatly restricted radial diffusion of O2 as well as H2 . At 60kPa pO2 , we found no radial diffusion of O2 across the barrier, and for H2 the barrier reduced radial diffusion by 73%. Similarly, RWL was reduced by 93% in roots with a ROL barrier. Our study showed that the root barrier to ROL not only completely blocks radial O2 diffusion under steep concentration gradients but is also a diffusive barrier to H2 and to water vapour. The strong correlation between ROL and RWL presents a case in which simple measurements of RWL can be used to predict ROL in screening studies with a focus on waterlogging tolerance.