Waterlogging-tolerant Genotypes Research Articles

Nitrogen Fertilization Alleviates Barley (Hordeum vulgare L.) Waterlogging

Waterlogging increasingly challenges crop production, affecting 10% of global arable land, necessitating the development of pragmatic strategies for mitigating the downside risk of yield penalty. Here, we conducted experiments under controlled (tank) and field conditions to evaluate the efficacy of nitrogenous fertiliser in alleviating waterlogging stress. Without intervention, we found that waterlogging reduced grain yields, spike numbers and shoot biomass, but had a de minimus impact on grain number per spike and increased grain weight. Soil fertiliser mitigated waterlogging damage, enhancing yields via increased spike numbers, with crop recovery post-waterlogging catalysed via improved tiller numbers, plant height and canopy greenness. Foliar nitrogen spray has little impact on crop recovery, possibly due to stomatal closure, while modest urea application during and after waterlogging yielded similar results to greater N application at the end of waterlogging. Waterlogging-tolerant genotypes (P-17 and P-52) showed superior growth and recovery during and after waterlogging compared to the waterlogging-sensitive genotypes (Planet and P-79). A comparison of fertiliser timing revealed that field fertilizer treatment two (F2: 90 kg·ha−1 at 28 DWL, 45 kg·ha−1 at sowing and 45 kg·ha−1 at 30 DR) yielded the highest and fertilizer treatment three (F3: 45 kg·ha−1 at sowing and 45 kg·ha−1 at 30 DR) recovered the lowest yield and spike number, while fertilizer treatment one (F1: 45 kg·ha−1 at 28 DWL, 45 kg·ha−1 at 0 DR, 45 kg·ha−1 at sowing and 45 kg·ha−1 at 30 DR) and four (F4: 90 kg·ha−1 at 0 DR, 45 kg·ha−1 at sowing and 45 kg·ha−1 at 30 DR) had the highest shoot biomass in the field. Treatment five (T5: 180 kg·ha−1 at 0 DR, 30 kg·ha−1 at sowing and 90 kg·ha−1 at 30 DR) presented the most favourable results in the tank. Our results provide rigorous evidence that long periods of waterlogging caused significant yield penalty, mainly due to decreased spike numbers. We contend that increasing fertiliser rates during waterlogging up to 90 kg·ha−1 can provoke crop growth and mitigate waterlogging-induced grain yield losses, and is more beneficial than applying nitrogen post-waterlogging.

Silver lining to a climate crisis in multiple prospects for alleviating crop waterlogging under future climates

Extreme weather events threaten food security, yet global assessments of impacts caused by crop waterlogging are rare. Here we first develop a paradigm that distils common stress patterns across environments, genotypes and climate horizons. Second, we embed improved process-based understanding into a farming systems model to discern changes in global crop waterlogging under future climates. Third, we develop avenues for adapting cropping systems to waterlogging contextualised by environment. We find that yield penalties caused by waterlogging increase from 3–11% historically to 10–20% by 2080, with penalties reflecting a trade-off between the duration of waterlogging and the timing of waterlogging relative to crop stage. We document greater potential for waterlogging-tolerant genotypes in environments with longer temperate growing seasons (e.g., UK, France, Russia, China), compared with environments with higher annualised ratios of evapotranspiration to precipitation (e.g., Australia). Under future climates, altering sowing time and adoption of waterlogging-tolerant genotypes reduces yield penalties by 18%, while earlier sowing of winter genotypes alleviates waterlogging by 8%. We highlight the serendipitous outcome wherein waterlogging stress patterns under present conditions are likely to be similar to those in the future, suggesting that adaptations for future climates could be designed using stress patterns realised today.

Screening of Onion (Allium cepa L.) Genotypes for Waterlogging Tolerance.

Onion production is severely affected by waterlogging conditions, which are created due to heavy rainfall. Hence, the identification of waterlogging-tolerant onion genotypes is crucial for increasing onion production. In the present study, 100 distinct onion genotypes were screened for waterlogging tolerance under artificial conditions by using the phenotypic approach in the monsoon season of 2017. Based on plant survival and recovery and changes in bulb weight, we identified 19 tolerant, 27 intermediate tolerant, and 54 highly sensitive onion genotypes. The tolerant genotypes exhibited higher plant survival and better recovery and bulb size, whereas sensitive genotypes exhibited higher plant mortality, poor recovery, and small bulb size under waterlogging conditions. Furthermore, a subset of 12 contrasting genotypes was selected for field trials during monsoon seasons 2018 and 2019. Results revealed that considerable variation in the morphological, physiological, and yield characteristics were observed across the genotypes under stress conditions. Waterlogging-tolerant genotypes, namely, Acc. 1666, Acc. 1622, W-355, W-208, KH-M-2, and RGP-5, exhibited higher plant height, leaf number, leaf area, leaf length, chlorophyll content, membrane stability index (MSI), pyruvic acid, antioxidant content, and bulb yield than sensitive genotypes under stress conditions. Furthermore, the principal component analysis biplot revealed a strong association of leaf number, leaf area, chlorophyll content, MSI, and bulb yield with tolerant genotypes under stress conditions. The study indicates that the waterlogging-tolerant onion genotypes with promising stress-adaptive traits can be used in plant breeding programs for developing waterlogging-tolerant onion varieties.

Transcriptome-wide identification and expression analysis of ERF family genes in Actinidia valvata during waterlogging stress

Recently, there has been a tremendous increase in the cultivated area of kiwifruit in China. However, the low tolerance of most cultivars to waterlogging largely halted its expansion in waterlogged areas. Previously, some genotypes from Actinidia valvata, like KR5, were proved to be highly tolerant for waterlogging stress. ERF transcription factors, belong to the AP2/ERF superfamily, have played key roles in adaptation to waterlogging stress in numerous plant species. In this study, a total of 131 AvERF genes were identified based on the full-length transcriptome analysis data from KR5. By clustering with Arabidopsis thaliana ERFs, 131 AvERF proteins were sorted into eleven clades and renamed as AvERF1 to AvERF131. Within the same group, similar motifs for AvERFs were found in all members by MEME online tool. According to FPKM analysis, the expression of AvERF-VIIs in KR5 under waterlogging conditions was strongly promoted compared to other group members. Six genes from AvERF-VIIs (AvERF73, AvERF75, AvERF77, AvERF78, AvERF79, and AvERF80) were chosen based on the higher fold changes in their expression against waterlogging. Moreover, their expression was evaluated in two tolerant genotypes: KR5 and KR1 from A. valvata, and two sensitive genotypes ‘Xuxiang’ and ‘Hayward’ from A. chinensis var. deliciosa during waterlogging stress by qRT-PCR. AvERF73 and AvERF78 were specifically induced in waterlogging-tolerant genotypes, but relatively low in the sensitive genotypes, indicating their positive roles in waterlogging tolerance. Both AvERF73 and AvERF78 had transcriptional activation activity. In the present study, we identified and characterized AvERFs into KR5 to reveal their importance in determining the waterlogging tolerance of kiwifruit.

Root length is proxy for high-throughput screening of waterlogging tolerance in Urochloa spp. grasses.

C4 perennial Urochloa spp. grasses are widely planted in extensive areas in the tropics. These areas are continuously facing waterlogging events, which limits plant growth and production. However, no commercial cultivar combining excellent waterlogging tolerance with superior biomass production and nutritional quality is available. The objective of this study was to identify root traits that can be used for selecting waterlogging tolerant species of Urochloa. Root respiration, root morphological, architectural and anatomical traits were evaluated in eight contrasting Urochloa spp. genotypes grown under aerated or deoxygenated stagnant solutions. Moreover, modelling of internal aeration was used to relate differences in root traits and root growth in waterlogged soils. Increased aerenchyma formation in roots, reduced stele area and development of a fully suberised exodermis are characteristics improving internal aeration of roots and therefore determining waterlogging tolerance in these C4 forage grasses. Waterlogging-tolerant genotypes had steeper root angles and greater root lengths than the waterlogging-sensitive genotypes. In stagnant conditions, waterlogging-tolerant genotypes had a greater proportion of aerenchyma and reduced stele area in root cross-sections, had deeper roots, steeper root angle and larger root biomass, which in turn, allowed for greater shoot biomass. Total root length had the strongest positive influence on shoot dry mass and can therefore be used as proxy for selecting waterlogging tolerant Urochloa genotypes.

Biochemical and yield evaluation of onion (Allium cepa L.) genotypes under waterlogging condition

The present investigation entitled “Biochemical and yield evaluation of onion (Allium cepa L.) genotypes under waterlogging condition” was carried out at ICAR-Directorate of Onion and Garlic Research, Rajgurunagar, Pune (Maharashtra). Onion crop is extremely sensitive to waterlogging or soil flooding stress due to its shallow root growth habit. The climate change and rainfall distribution pattern most of the onion growing belt might be subjected to heavy rainfall leading to soil flooding condition and cope up with such situation need to identify the improved onion genotypes with better adaptive traits and tolerance for waterlogging condition Therefore, the main objective of the present study was screening of elite genotypes for water logging tolerance under pot condition. The experiment was laid out in factorial CRD for pot condition during kharif, 2018. The pot experiment was conducted in rainout shelter using plastic pot and plants were treated with creating artificial waterlogging condition with the help of tank pit and another set were kept outside in rainout shelter as control. The experimental materials comprises of 17 onion entries including red and white onion entries. The seedlings of each entry were raised from seeds in nursery for 45 days with recommended cultural practices and transplanted in pot. The biochemical traits leaf antioxidant, leaf flavonoids and phenol content exhibited maximum in genotype RGP 5 under waterlogging condition. The waterlogging condition was increased quality traits which producing more secondary metabolites for defense strategy of the plant. Further, the yield attribute like bulb yield percent was minimum decreased in genotype RGP 5 with the percent reduction of 18.59% and the genotype W 344 recorded maximum percent reduction with decline by 83.49% under water logging treatment. It may due the water logging condition inhibits the translocation of assimilates from source organs to sink organ. Therefore, on the basis of overall yield reduction percentage and other important traits, genotype RGP 5 can be categorized as water logging tolerant genotypes, whereas genotype W 344 and W 448 recognized as water logging sensitive genotypes among all the tested onion genotypes.

Assay of Genetic Architecture for Identification of Waterlogging Tolerant Pigeonpea Germplasm

The experiment was conducted to identify the waterlogging stress tolerant genotypes in pigeonpea. Waterlogging treatment was given to the plants at vegetative stage after treatment the survival rate was assessed. Out of 128 germplasm pool, 38 survived and the survival rate was estimated along with Mahalanobis D2 cluster analysis. The range of survival percentage for both pot and field were found between 26.6 and 73.3 with the standard deviation of 14.82 for pot screening and 14.29 for field screening. The pot survival percentage mean for all 38 accessions were found higher than field survival which clearly indicates that environment poses an effect on the performance of the genotypes. The Mahalanobis cluster analysis revealed five clusters. Out of five clusters, two were found comparatively tolerant than the others. The tolerant germplasm can also be used as donor parents in hybridization programs for development of water logging-tolerant genotypes. The identified tolerant germplasms may be utilized to incorporate waterlogging tolerance in the short-duration pigeonpea pool.

Waterlogging tolerance in barley is associated with faster aerenchyma formation in adventitious roots

Plant adaptation to waterlogged conditions requires a set of morphological and physiological/biochemical changes. The formation of aerenchyma is one of the most crucial adaptive traits for waterlogging tolerance. Enzymatic scavenging may also potentially contribute to waterlogging tolerance by providing detoxification of reactive oxygen species (ROS). Changes of root porosity (as an indicator of aerenchyma formation) and activities in leaves of four major antioxidant enzymes, γ-amino butyric acid (GABA) and lactic acid contents in roots were evaluated in six barley genotypes contrasting in waterlogging tolerance. Soil waterlogging caused significant increases in adventitious root porosity in all genotypes. Waterlogging-tolerant genotypes showed not only significantly higher adventitious root porosity than sensitive genotypes but also much faster development of aerenchyma. The greatest difference in adventitious root porosity among genotypes was observed after 7 days of waterlogging treatment. At the same time, antioxidant enzyme activities in leaves, GABA and lactic acid contents in roots did not correlate with waterlogging tolerance. A faster formation of aerenchyma in adventitious roots is one of the key factors for waterlogging tolerance in barley. This protocol is recommended to be applied in future studies to identify molecular markers linked to this trait using appropriate mapping populations.

Mechanism of water-logging tolerance in pigeonpea

A study was undertaken to identify the morphophysiological traits associated with water-logging tolerance in pigeonpea [Cajanus cajan L. (Millsp.)]. The formation of aerenchyma cells, lenticels, and adventitious roots in the tolerant genotypes were found to be associated with waterlogging tolerance in pigeonpea. The tolerant genotypes, namely, ICP 5028, ICPH 2431, ICPL 87119, ICPH 2740, ICPL 149, ICPL 20241, and MAL15, exhibited varying responses to hypoxic conditions. Formation of aerenchymatous cells was common in all the water-logging tolerant genotypes. Besides this, five tolerant genotypes (ICP 5028, ICPH 2431, ICPL 87119, ICPH 2740 and MAL 15) developed lenticels, while ICPL 149 and ICPL 20241 formed prominent adventitious roots. None of these traits was present in the susceptible genotypes. These traits developed only when exposed to water-logging stress and facilitated oxygen supply from stem to roots helping in respiration of the suffering plants. Potential breeding strategies to develop pigeonpea genotypes with enhanced levels of waterlogging tolerance are discussed.

Linking waterlogging tolerance with Mn²⁺ toxicity: a case study for barley.

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 Mn(2+) that can be toxic to plants if above a specific threshold. This work aimed to quantify the relative contribution of Mn(2+) 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 (1mm) amounts of Mn(2+) in the root rhizosphere. Under Mn(2+) 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 Mn(2+) toxicity symptoms, suggesting that various Mn(2+) tolerance mechanisms might operate in different tolerant genotypes, i.e. avoidance versus tissue tolerance. The overall significant (r=0.60) correlation between tolerance to Mn(2+) toxicity and waterlogging in barley suggests that plant breeding for tolerance to waterlogging traits may be advanced by targeting mechanisms conferring tolerance to Mn(2+) toxicity, at least in this species.

Genetic and cultural improvement of soybean for waterlogged conditions in Asia

Soybean (Glycine max (L.) Merr.) is vulnerable to waterlogging, which threatens soybean productivity in humid regions of Asia. Waterlogging can happen during any growth stage of soybean, but flooding stress before, at or after germination causes severe seed and seedling damage, resulting in substantial reduction of grain yield at maturity. Under waterlogged conditions, seeds imbibe rapidly, destroying seed tissues due to abrupt swelling of the cells. Anatomical observations during water absorption of seeds revealed that the aleurone layer blocks abrupt water penetration into the embryo regardless of genotype. Based on these observations, genetic analyses of waterlogging-tolerant genotypes are currently in progress and attempts to incorporate the genes responsible for such tolerance are being made. Among cultural measures to alleviate waterlogging-induced damage during germination, pre-hydrating seeds prior to sowing proved to be most effective. After emergence, waterlogging impairs root function, primarily due to hypoxia, and thereby the capacity for nutrient uptake and growth. Molecular characterization of enzymes expressed in growing plants subjected to waterlogging treatment has identified several genes involved in anaerobic respiration. In addition, some soybean cultivars were found to form aerenchyma, which transports oxygen from aboveground tissues to the root system, in response to waterlogging. These phenomena should be exploited for breeding waterlogging-tolerant cultivars. Cultural methods including partial tillage and adjustment of the water table also effectively mitigate damage caused by waterlogging. Integration of these approaches should lead to stable soybean production in humid agricultural areas of Asia.

Replacement of cv. Yarloop in swards by new genotypes of Trifolium subterraneum L. subsp. yanninicum and the effects of defoliation

Yarloop is a waterlogging-tolerant cultivar of Trifolium subterraneum subsp. yanninicum; it is highly oestrogenic. It is known to be a strong competitor and is widely grown in south-western Australia. Three new low-oestrogenic, waterlogging-tolerant genotypes of subsp. yanninicum were grown in monoculture, and in binary mixture in competition with cv. Yarloop, in large boxes in a glasshouse. Of the three, Y111 and Y136 gave satisfactory growth relative to Yarloop, and exhibited similar flowering and seed production; cv. Larisa, a late-maturing type, performed well until flowering and had a lower seed number than Yarloop. A second experiment examined the effects of defoliation during the vegetative phase on the relative performance of cv. Yarloop and cv. Larisa growing in mixtures of varying proportions. Two overall densities were used. The dominance of Yarloop over Larisa in uncut swards, due to its more vigorous growth habit, was nullified by regular cutting. The agronomic implications of the results are discussed.