Waterlogging Stress Research Articles

Effects of glutathione on waterlogging-induced damage in sesame crop

Sesame (Sesamum indicum) is an important oil crop, occupying the seventh position in the edible oil industry; however, it is relatively sensitive to waterlogging (WL) stress. Reduced glutathione (GSH) is known to have mitigating effects against various abiotic stresses in plants; however, its exploration to improve WL tolerance in sesame is still elusive. In this study, we investigated the multiple effects of exogenously applied GSH in sesame plants subjected to WL for 3 days. Our results showed improvement in growth and biomass production of GSH-sprayed waterlogged sesame when compared with WL-stressed counterpart alone. The improved performance of GSH-sprayed WL-stressed plants was supported by the increased leaf area, the levels of photosynthetic pigments and gas exchange attributes, and chlorophyll fluorescence parameters. Exogenous GSH treatment significantly increased the levels of total soluble sugars and total free amino acids in the leaves of sesame plants for the improvement of water balance under WL conditions. Accumulations of superoxide and hydrogen peroxide, enhancement of malondialdehyde level, and electrolyte leakage in sesame leaves indicated evident oxidative damage induced by WL. On the other hand, exogenous GSH application diminished oxidative stress by enhancing the activities of catalase, ascorbate peroxidase, peroxidase, glutathione peroxidase, and glutathione S-transferase, as well as total flavonoid and GSH levels in the leaf tissues. Furthermore, GSH supplementation to WL plants increased the transcript levels of numerous antioxidant defense-related genes, such as SiCAT1, SiCATX1, SiAPX3, SiPOD40, SiPOD44, SiGPX4, SiPHGPX1, SiGSTU23, and SiGSTU25 in shoots, corresponding to enhanced activities of respective antioxidant enzymes. Our results highlight the potential roles of GSH in modulating adaptive mechanisms of sesame plants for reduction of WL-induced damage, and this GSH-mediated effective strategy could be implemented at the field level to sustain sesame production under WL conditions.

Ethylene regulates aerenchyma formation in cotton under hypoxia stress by inducing the accumulation of reactive oxygen species

Aerenchyma formation is one of the most effective mechanisms adapted by plants to cope with waterlogging (WL). It which reduces the negative effects of WL by facilitating gas diffusion within roots. To understand the response of cotton roots to WL, hypoxia-tolerant genotype Cx094 and hypoxia-sensitive genotype Wang18 were used in this study. The seedlings of two varieties were treated by three methods: flooding in pots as Treatment 1 (flooding), low oxygen with agar solution as Treatment 2 (flooding + agar) and hypoxia with agar solution and nitrogen gas as Treatment 3 (flooding + agar + N 2 ). The results showed that in Cx094, the highest proportion of aerenchyma was found in Treatment 2, with no corresponding aerenchyma formation in Wang18. Further studies were carried out in Treatment 2 to check the aerenchyma formation in six cotton accessions and the results showed that aerenchyma only formed in hypoxia-tolerance genotypes, confirming the important role of aerenchyma formation in WL-tolerant genotypes. The unique characteristic of cotton is that four symmetrical aerenchyma were formed under WL stress, and they appeared one by one. We also showed that hypoxia signal induced expression of ACS and ACO genes, resulting more ethylene synthesis in hypoxia-tolerant genotypes. Moreover, ethylene induced reactive oxygen species (ROS) accumulated by up-regulation of RBOHs expression and down-regulation of MT-3a expression. Finally, ROS caused up-regulation of CEL and XET expressions to induce programmed cell death, and result in lysigenous aerenchyma. Exogenous ethylene inhibitor decreased the formation of aerenchyma in Cx094, while ethephon, an ethylene precursor, promote the formation of aerenchyma in Wang18, signifying the important role of ethylene in the formation of aerenchyma in cotton. • The first time to report aerenchyma in cotton. • Ethylene induced ROS accumulation. • ROS promotes PCD occurrence. • Ethylene promotes aerenchyma formation in cotton.

The Stomatal Conductance and Fv/Fm as the Indicators of Stress Tolerance of Avocado Seedlings under Short-Term Waterlogging

Avocados may suffer from short-term waterlogging stress when exposed to high temperatures and heavy rainfall during the summer in Taiwan. We compared the waterlogging responses of own-rooted and grafted seedlings of two Taiwan cultivars, ‘Black-Beauty’ and ‘Hung-Hsin-Yuan’, by stomatal conductance (gs) and chlorophyll fluorescence parameters. Four-day waterlogging and four-day post-waterlogging recovery periods were investigated. Both gs and Fv/Fm of own-rooted seedlings of two cultivars were significant reductions in response to short-term waterlogging. The grafted seedlings on the same cultivar rootstock were evaluated by gs and Fv/Fm during the growth and the growth cessation periods, respectively. The combined responses of gs and Fv/Fm under short-term waterlogging showed that ‘Black-Beauty’ was sensitive to stress because of decreased gs after waterlogging or decreased Fv/Fm after the two-day recovery period. ‘Hung-Hsin-Yuan’ showed more tolerance to waterlogging stress, especially during the growth cessation. This indicates that the vegetative dormancy may affect the evaluation of the stress response of avocados. Our results revealed that gs and Fv/Fm can be effective indicators in the four-day waterlogging of avocado, and the growth status of avocado seedlings should be considered during stress-tolerant variety selection.

Photosynthetic and Morphological Responses of Sacha Inchi (Plukenetia volubilis L.) to Waterlogging Stress.

Sacha inchi (Plukenetia volubilis L.) is an important oilseed crop that is rich in fatty acids and protein. Climate-change-related stresses, such as chilling, high temperature, and waterlogging can cause severe production loss in this crop. In this study, we investigated the photosynthetic responses of sacha inchi seedlings to short-term waterlogging and their morphological changes after long-term waterlogging stress. Sacha inchi CO2 uptake, stomatal conductance, and transpiration rate are affected by temperature and light intensity. The seedlings had a high CO2 uptake (>10 μmol m−2s−1) during the daytime (08:00 to 15:00), and at 32 and 36 °C. At 32 °C, CO2 uptake peaked at irradiations of 1000 and 1500 µmol m−2s−1, and plants could still perform photosynthesis at high-intensity radiation of 2000–3000 µmol m−2s−1. However, after 5 days of waterlogging (5 DAF) sacha inchi seedlings significantly reduced their photosynthetic ability. The CO2 uptake, stomatal conductance, Fv/Fm, ETR, and qP, etc., of the susceptible genotypes, were significantly decreased and their wilting percentage was higher than 50% at 5 DAF. This led to a higher wilting percentage at 7 days post-recovery. Among the four lines assessed, Line 27 had a high photosynthetic capability and showed the best waterlogging tolerance. We screened many seedlings for long-term waterlogging tolerance and discovered that some seedlings can produce adventitious roots (AR) and survive after two weeks of waterlogging. Hence, AR could be a critical morphological adaptation to waterlogging in this crop. In summary, these results suggest that improvement in waterlogging tolerance has considerable potential for increasing the sustainable production of sacha inchi.

Melatonin and KNO3 Application Improves Growth, Physiological and Biochemical Characteristics of Maize Seedlings under Waterlogging Stress Conditions.

Simple SummaryWaterlogging is one of the serious abiotic stresses that retards plant growth and reduces crop productivity. Therefore, exploring effective ways for alleviating the impacts of waterlogging stress has important theoretical and practical applications. Melatonin is a pleiotropic molecule that influences many diverse actions to enhance plant growth. Therefore, investigating efficient waterlogging mitigation measures has both theoretical and practical significance. The objectives of the present research were to examine the efficiency of melatonin and KNO3 seed soaking and foliar application on alleviating the waterlogging inhibited growth performance of maize seedlings. The results showed that melatonin and KNO3 significantly improved the plant growth and biochemical parameters of maize seedlings under waterlogging stress conditions. Overall, the application of 100 µM melatonin with 0.50 g KNO3 via seed soaking and foliar spray can be used as a potential mitigating strategy for improving the growth of maize seedlings and alleviating the ill effects of waterlogging stress.Waterlogging is one of the serious abiotic stresses that inhibits crop growth and reduces productivity. Therefore, investigating efficient waterlogging mitigation measures has both theoretical and practical significance. The objectives of the present research were to examine the efficiency of melatonin and KNO3 seed soaking and foliar application on alleviating the waterlogging inhibited growth performance of maize seedlings. In this study, 100 µM melatonin and different levels (0.25, 0.50 and 0.75 g) of potassium nitrate (KNO3) were used in seed soaking and foliar applications. For foliar application, treatments were applied at the 7th leaf stage one week after the imposition of waterlogging stress. The results showed that melatonin with KNO3 significantly improved the plant growth and biochemical parameters of maize seedlings under waterlogging stress conditions. However, the application of melatonin with KNO3 treatments increased plant growth characteristics, chlorophyll content, and the net photosynthetic rate at a variable rate under waterlogging stress. Furthermore, melatonin with KNO3 treatments significantly reduced the accumulation of hydrogen peroxide (H2O2) and malondialdehyde (MDA), and it decreased the activity of pyruvate decarboxylase and alcohol dehydrogenase, while increasing enzymatic activities and soluble protein content of maize seedlings under waterlogging stress conditions. Overall, our results indicated that seed soaking with 100 µM melatonin and 0.50 g KNO3 was the most effective treatment that significantly improved the plant growth characteristics, chlorophyll content, photosynthetic rate, and enzymatic activity of maize seedling under waterlogging conditions.

Exogenous salicylic acid and kinetin modulate reactive oxygen species metabolism and glyoxalase system to confer waterlogging stress tolerance in soybean (Glycine max L.)

We conducted this study to investigate the positive effects of foliar-applied salicylic acid (SA) and kinetin (KN) in improving waterlogging stress tolerance, by upregulating reactive oxygen species (ROS) metabolism and antioxidant defense including glyoxalase system in soybean (Glycine max cv. Sohag) grown under different levels of waterlogging. Waterlogging was imposed on plants at 15 days after sowing at four different durations viz. waterlogging for 0 days (W0), waterlogging for 3 days (W3), waterlogging for 6 days (W6), waterlogging for 9 days (W9), and plants were supplemented with exogenous SA (0.5 mM) and KN (0.1 mM). Waterlogging increased lipid peroxidation (malondialdehyde content), hydrogen peroxide content, leaf electrolyte leakage, proline content, and glutathione S-transferase (GST) activity while ascorbate peroxidase (APX), monodehydroascorbate reductase (MDHAR), dehydroascorbate reductase (DHAR), glutathione reductase (GR), catalase (CAT), glutathione peroxidase (GPX), peroxidase (POD), glyoxalase I (Gly I) and glyoxalase II (Gly II) activities were decreased. On the contrary, exogenous SA and KN reduced the MDA content, H2O2 content, proline content, and leaf electrolyte leakage under waterlogging. Further, supplementation of SA and KN enhanced the activity of APX, MDHAR, DHAR, GR, CAT, GST, GPX, POD, Gly I, and Gly II under waterlogging stress. In the current study, the results indicate that both exogenous SA and KN effectively improved the ROS metabolism and waterlogging stress tolerance in soybean by enhancing the antioxidant defense and upregulating the glyoxalase system.

Assessing Waterlogging Stress Level of Winter Wheat from Hyperspectral Imagery Based on Harmonic Analysis

Frequent waterlogging disasters can have serious effects on regional ecology, food safety, and socioeconomic sustainable development. Early monitoring of waterlogging stress levels is vital for accurate production input management and reduction of crop production-related risks. In this study, a pot experiment on winter wheat was designed using three varieties and seven gradients of waterlogging stress. Hyperspectral imagery of the winter wheat canopy in the jointing stage, heading stage, flowering stage, filling stage, and maturation stage were measured and then classified. Wavebands of imaging data were screened. Waterlogging stress level was assessed by a combined harmonic analysis method, and application of this method at field scale was discussed preliminarily. Results show that compared to the k-nearest neighbor and support vector machine algorithms, the random forest algorithm is the best batch classification method for hyperspectral imagery of potted winter wheat. It can recognize waterlogging stress well in the wavebands of red absorption valley (RW: 640–680 nm), red-edge (RE: 670–737 nm), and near-infrared (NIR: 700–900 nm). In the RW region, amplitudes of the first three harmonic sub-signals (c1, c2, and c3) can be used as indexes to recognize the waterlogging stress level that each winter wheat variety undertakes. The third harmonic sub-signal amplitude c3 of the RE region is also suitable for judging stress levels of JM31 (one of the three varieties which is highly sensitive to water content). This study has important theoretical significance and practical application values related to the accurate control of waterlogging stress, and functions as a new method to monitor other types of environmental stress levels such as drought stress, freezing stress, and high-temperature stress levels.

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.

Responses of shoot biomass accumulation, distribution, and nitrogen use efficiency of maize to nitrogen application rates under waterlogging

Waterlogging (WL) during the early growing stage is one of the most important environmental factors limiting maize (Zea mays L.) production. The application of nitrogen (N) fertilizer is important to maintain normal plant growth and defense against abiotic stresses. However, the effects of N fertilization on biomass accumulation and partitioning, as well as N utilization in maize under WL stress remains unclear. Thus, we conducted a two-year field experiment at Jingzhou City, Central China to investigate the effects of varying N fertilizer application rates (0, 90, 180, 270, and 360 kg N ha−1) on shoot biomass accumulation and its distribution, N uptake, and N use efficiency in maize under well-watered (WW) conditions throughout the maize growing season and WL for 6 d at the sixth leaf stage. Compared to the WW condition, WL significantly reduced shoot biomass, N accumulation, harvest index, N harvest index, nitrate reductase activity, N use efficiency, and N partial factor productivity at all N application rates. Moreover, these parameters (excluding N partial factor productivity) increased with increasing N application rates (up to 360 kg N ha−1) under WL, suggesting that a high N rate (such as 360 kg N ha−1) could improve the accumulation and distribution of shoot biomass and N utilization of waterlogged maize. The enhanced shoot biomass, nitrate reductase activity, N accumulation, and N use efficiency were related to increased root biomass and root length density at higher N treatments under WL. In addition, compared with other N treatments, 360 kg N ha−1 resulted in a better proportion of biomass distribution in the kernel and improved transfer of biomass from the vegetative organs to grain under WL, which accounted for the enhanced harvest index. Therefore, an appropriate increase in the nitrogen application rates (up to 360 kg N ha−1) helped to improve biomass accumulation in the shoot and its transfer to the grain, together with N use efficiency in maize under early (sixth leaf)-stage waterlogging.

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.

Fertiliser and soil moisture regulation mitigates waterlogging stress injury of Zanthoxylum armatum seedlings in potted condition

Fertiliser and soil moisture regulation mitigates waterlogging stress injury of Zanthoxylum armatum seedlings in potted condition

English

From many years, global cotton production suffers from waterlogging stress. Climatic variation and heavy rainfall conditions with poor internal soil drainage mechanism limits the growth and development of cotton crop due to waterlogging. It reduced the soil oxygen which causes the severe yield losses and sometimes even failure of a crop. Indeterminate growth habit of cotton plant makes it able to adapt this stress by activation of the escape, self compensation and quiescence mechanism. The reduction of biomass, development of adventitious roots and accelerated growth mechanism, all are associated with adaption and tolerance mechanisms. Waterlogging significantly affect the cellulose and sucrose content of fiber in cotton. Sodic soils also exacerbate the waterlogging stress because these soils already suffer by aeration stress. Different growth stages are effect differently but flowering and boll setting stage is more sensitive to waterlogging conditions.

Climate change shifts forward flowering and reduces crop waterlogging stress

Climate change will drive increased frequencies of extreme climatic events. Despite this, there is little scholarly information on the extent to which waterlogging caused by extreme rainfall events will impact on crop physiological behaviour. To improve the ability to reliably model crop growth and development under soil waterlogging stress, we advanced the process-basis of waterlogging in the farming systems model Agricultural Systems Production Systems sIMulator. Our new mathematical description of waterlogging adequately represented waterlogging stress effects on the development, biomass and grain yield of many commercial Australian barley genotypes. We then used the improved model to examine how optimal flowering periods (OFPs, the point at which long-term abiotic stresses are minimal) change under historical and future climates in waterlogging-prone environments, and found that climate change will reduce waterlogging stress and shift forward OFP (26 d earlier on average across locations). For the emissions scenario representative concentration pathway 8.5 at 2090, waterlogging stresses diminished but this was not enough to prevent substantial yield reduction due to increasingly severe high temperature stress (−35% average reduction in yield across locations, genotypes and sowing dates). It was shown that seasonal waterlogging stress patterns under future conditions will be similar to those occurring historically. Yield reduction caused by waterlogging stress was 6% and 4% on average across sites under historical and future climates. To adapt, both genotypic and management adaptations will be required: earlier sowing and planting waterlogging tolerant genotypes mitigate yield penalty caused by waterlogging by up to 26% and 24% under historical and future climates. We conclude that even though the prevalence of waterlogging in future will diminish, climate change and extreme climatic events will have substantial and perverse effects on the productivity and sustainability of Australian farms.

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.

Physiological mechanisms of pre-anthesis waterlogging priming on waterlogging stress tolerance under post-anthesis in wheat

<p id="C3">In order to investigate the responses and mechanisms of different wheat varieties to waterlogging stress and waterlogging priming, waterlogging priming was conducted for two days at the four-leaf and six-leaf stages, respectively, and waterlogging stress was performed for five days at post-anthesis using wheat varieties with different responses to waterlogging stress and waterlogging priming as experimental materials. Results showed that waterlogging stress significantly reduced chlorophyll content (SPAD) and actual photochemical efficiency (<italic>Φ</italic>_PSII), inhibited the accumulation of post-anthesis photosynthetic assimilation accumulation (PAA), decreased kernel weight and grain yield. Compared with the waterlogging-sensitive varieties, the waterlogging-tolerance varieties could maintain higher SPAD, <italic>Φ</italic>_PSII and PAA, and higher activities of superoxide dismutase (SOD), Catalase (CAT), ascorbate peroxidase (APX) and glutathione reductase (GR), lower contents of H₂O₂, O₂^܋production rate and malondialdehyde (MDA) under post-anthesis waterlogging stress. Compared with non-primed plants, primed plants could maintain higher chlorophyll fluorescence performance and higher activities of antioxidant enzymes. Compared with the waterlogging priming-insensitive varieties, the priming-sensitive varieties increased SPAD (8.8%) and <italic>Φ</italic>_PSII (17.6%), decreased the non-regulated energy dissipation <italic>Φ</italic>_NO (10.7%) and the regulation energy dissipation <italic>Φ</italic>_NPQ (16.5%), increased the activities of SOD (15.8%), CAT (17.8%), APX (8.9%) and GR (30.7%), increased the contents of total soluble sugar (17.5%) and sucrose (21.6%), increased remobilization efficiency of pre-anthesis stored dry matter (REP, 20.0%) and PAA (10.8%). The waterlogging tolerant varieties could maintain higher photosynthesis rate, dry matter translocation capacity and activities of antioxidant enzymes. Compared with waterlogging sensitive varieties, the increase amplitude of photosynthetic ability and antioxidant enzyme activity of priming-sensitive cultivars was higher under waterlogging stress.

In silico characterization and homology modeling of cytosolic APX gene predicts novel glycine residue modulating waterlogging stress response in pigeon pea.

Ascorbate peroxidase (APX) is a member of the family of heme-containing peroxidases having a similar structure with Cytochrome c peroxidase (CCP) that effectively scavenge cytosolic and chloroplastic hydrogen peroxide (H2O2) under various stresses. In this study, computational characterization and homology analysis of APX protein from waterlogging tolerant (ICPL 84023) and sensitive (ICP 7035) pigeon pea genotypes were carried out resulting in 100% homology with Glycine max in case of former and 99% in later genotypes respectively with 97.39% alignment coverage among each other. The model structure was further refined by various tools like PROCHECK, ProSA, and Verify3D. The planned model of the APX enzyme was then tested to dock with H2O2along with molecular dynamics (MD) simulation analysis. The docked complex of ICPL 84023 showed the best G-score (23.39 kcal/mol) in comparison to ICP 7035 (16.74 kcal/mol) depicting the higher production of APX for scavenging reactive oxygen species (ROS) production making this genotype more tolerant. The important binding residues in the ICPL 84023-H2O2complex (SER1, THR4, GLU23, and GLY13) have shown less fluctuation than the ICP 7035-H2O2 complex (SER1, THR4, and GLU23). Overall, our results showed that amino acid residue glycine in ICPL 84023 APX gene has a high binding affinity with H2O2 which could be a key factor associated with waterlogging stress tolerance in pigeon pea.

Waterlogging tolerance of the common reedsPhragmites mauritianusandP. australis

AbstractThis study compared the responses ofPhragmites mauritianusandP. australisto waterlogging stress for 5 months. Plants were subjected to a 2 × 4 factorial experiment with two species and four soil moisture regimes: well drained (WD), half flooded (½F), flooded/drained at weekly intervals (F/D) and continuously flooded (F). Soil redox potential (Eh) was high in the WD (+138 to +126 mV) and low in the F treatments (−360 to −401 mV). Flooding increased plant height, number of culms, shoot elongation and total dry biomass accumulation in both species. In the flooded treatments, there was greater biomass allocation to above ground than below ground components, which contributed to increases in above‐ground/below‐ground ratios. In the flooded treatments, specific gravity of culms decreased by 18% inP. australisand by 10% inP. mauritianusindicating greater aerenchyma with waterlogging. In both reeds, flooding induced numerous adventitious roots from the base of the culms. In the F treatments, plant height, number of culms, total dry biomass accumulation and aerenchyma development were greater inP. australisthan inP. mauritianus. These data suggest thatP. australishas a competitive edge overP. mauritianusunder waterlogged conditions.

Genotypic variations in nitrate respiration along with potassium nitrate treatment - accountable for water logging tolerance in maize

The present investigation was undertaken to study the effects of water logging and potassium nitrate treatment on the status of nitrate metabolism in maize genotypes, I 167 and LM 5, showing differential tolerance towards water logging stress. Water logging reduced length and biomass of LM 5 (stress susceptible) seedlings to a higher extent than those of I 167 (stress tolerant). Foliar spray of 1% KNO3 increased seedling growth in both the genotypes. The water logged I 167 seedlings maintained their nitrate levels more efficiently than those of LM 5 seedlings. The parallel increase in NO content in the hypoxic roots showed the effective utilization of NO in nitrate respiration pathway of I 167 seedlings. The increased NO content in the shoots of water logged LM 5 seedlings irrespective of their reduced NR activity showed that the susceptible genotype might have preferentially utilized nitrite ions for NO generation rather than ammonium assimilation during early stage of water logging stress. KNO3 spray increased alanine amino transferase (AlaAT) and glutamine oxoglutarate amino transferase (GOGAT) activities along with an increase in amino acid and protein content of I 167 shoots that might be responsible for better assimilation of amino acids in the tolerant genotype. It may thus be concluded that there were genotypic differences in nitrate metabolism under water logging stress and potassium nitrate significantly improved ammonium assimilation of maize genotypes.

Detection of cotton waterlogging stress based on hyperspectral images and convolutional neural network

Waterlogging in the early stage of cotton will reduce the number of bolls and do harm to yield. Early detection of waterlogging will help farmers to adjust cotton management and save the loss. To evaluate the application of deep learning for the detection of early waterlogging, this study applied a convolutional neural network (CNN) to classify different durations of waterlogging stress (0, 2, 4, 6, 8, 10 d) based on hyperspectral images (HSIs) of cotton leaves. An experiment was designed to simulate the situation of cotton under waterlogging stress and collect HSIs of visible and near-infrared (VNIR 450-950 nm) spectra with 126 bands 66 d after cotton sowing (66 DAS). It was found the spectral curve reflectance of waterlogging cotton was higher than that of non-waterlogging cotton. Especially near 550 nm and 750 nm, and the spectral curve increased with durations of waterlogging stress and there were ‘blue shift’ phenomena for the position of the red edge of the spectra. The first principal components of HSIs after band randomly discarding and principal component analysis (PCA) were used to build a dataset. GoogLeNet Inception-v3 (GLNI-v3) and VGG-16 models were selected to detect cotton waterlogging stress with the dataset. The results showed that the average time for a round training for GLNI-v3 was 13.337 s, with a classification accuracy of 96.95% and a loss value of 0.09431. The average time for a round training for VGG-16 was 21.470 s, with a classification accuracy of 97.00% and a loss value of 0.17912. Though these two models had similar classification accuracy and loss value, GLNI-v3 achieved a high accuracy with fewer training iterations. The durations of waterlogging stress of cotton in a short-term can be detected by HSIs of cotton leaves and CNN models are suitable for the classification of HSIs, and this method can provide support for cotton yield estimation and loss assessment after waterlogging. Keywords: cotton, waterlogging, hyperspectral image, convolutional neural network DOI: 10.25165/j.ijabe.20211402.6023 Citation: Zhao J, Pan F J, Li Z M, Lan Y B, Lu L Q, Yang D J, et al. Detection of cotton waterlogging stress based on hyperspectral images and convolutional neural network. Int J Agric & Biol Eng, 2021; 14(2): 167–174.

Genome-wide identification and expression profiling of AP2/ERF superfamily genes under stress conditions in dark jute (Corchorus olitorius L.)

The ethylene-responsive element (AP2/ERF) is one of the keys and conserved transcription factors (TF) in plants that play a vital role in regulating plant growth, development and stress response. A total of 119 CoAP2/ERF genes were identified from the dark jute genome, one of the most important bast fibre crops. Among these, 17 were AP2, 97 ERF, 4 RAV and 1 Soloist gene family. Phylogenetic analysis revealed that the AP2/ERF genes can be divided into 10 groups. These genes were distributed randomly across the linkage groups and found three tandem and eight segmental duplications which arose from ancient duplication events. Expression profiling of CoAP2/ERF genes was assessed using RNA-Seq data and qRT-PCR analysis in tissues during development and under biotic (Macrophomina phaseolina) and abiotic (waterlogging, salinity, drought) stresses. CoERF-21, CoERF-34 and CoERF-39 genes were significantly upregulated during waterlogging stress and CoDREB-11, CoDREB-14 and CoRAV-01 genes were upregulated under salinity and drought stress condition. Gene evolution analysis among the Malvaceae family showed dark jute were separated 14 and 22 Mya from cacao and cotton respectively and expression correlation analysis revealed the functions of superfamily genes were expanded and enhanced through gene duplication. These findings provide new insights into AP2/ERF gene evolution, divergence in dark jute and considered a valuable resource for further functional validation as well as for utilization in stress resistance variety development program.