Flooding Tolerance Research Articles

Testing mechanisms underlying responses of plant functional traits to flooding duration gradient in a lakeshore meadow

Flooding duration is a major factor determining wetland plant growth and community composition. While there have been extensive studies on how direct effects of flooding duration on plant functional traits, very few have tested the indirect effects on these traits, including those arising from competition. We hypothesized that there would be a shift in importance of competition ability and flooding tolerance to functional traits along the flooding duration gradient. We investigated plant functional traits along a flooding duration gradient for two-dominant wetland plant species (Carex cinerascens and Phalaris arundinacea) in a lakeshore meadow of Poyang Lake, China. We found that these two species tended to have different strategies to adapt to flooding stress. P. arundinacea tended to adopt escape strategy with high growth rate (e.g. greater height, specific leaf area, and leaf N and P content) at longer flooding duration, while C. cinerascens tended to adopt more quiescence strategy, with only 5 of 13 of its traits showing a significant response. With shorter flooding duration, both species tended to have lower leaf N and P content, indicating greater nutrient limitation. Meanwhile, relative abundance of C. cinerascens with relatively higher belowground nutrient competition ability (i.e. greater root/shoot biomass ratio) decreased with flooding duration. These results suggest that belowground competition intensifies at shorter flooding duration, because of increased nutrient limitation with increased productivity. Therefore, our study indicates that both flooding stress and nutrient competition could affect plant functional traits along a flooding duration gradient.

Using leaf nutrient stoichiometry as an indicator of flood tolerance and eutrophication in the riparian zone of the Lijang River

Leaf carbon (C), nitrogen (N), and phosphorus (P) concentrations and corresponding ratios are indicators of ecological processes. How plant C, N and P stoichiometry responds to environmental stresses under variable flooding regimes in riparian systems is presently unclear. In this study, we evaluated the characteristics of C, N and P stoichiometry of riparian plants across different seasons and inundation zones along the Lijiang River in China. Our analysis revealed that leaf C, N and P concentrations and C: N: P ratios varied extensively. Leaf N and P concentrations were lower in spring than in autumn, whereas leaf C concentration and C: N, C: P and N: P ratios were higher in spring. Total leaf N and P concentrations were significantly higher and C: N and C: P ratios were significantly lower in the severe inundation zone than the mild inundation zone. Among different plant functional types, grasses in the severe inundation zone had relatively higher N and P concentrations. In general, plants in the Lijiang River riparian zone used a quiescent strategy to cope with flooding stress. Herbaceous plants showed the greatest adaptation to flooding environments. A tendency towards N limitation of plant growth may exist due to anthropogenic eutrophication. Our findings, which highlight the influence of season and flooding on plant leaf stoichiometric characteristics, may help guide the rehabilitation and conservation of riparian ecosystems.

Physiological Mechanism and Nutrient Management Strategies for Flood Tolerance in Rice Grown in Lowland Flood Prone Ecosystem

In flood-prone areas, rice must have flood tolerance characteristics either through genotypic selections or by nutrient application management strategies. The current study was conducted at ICAR Research Complex for Eastern Region, Patna during the wet season to investigate the effect of post-flood nutrient application methods on submerged rice survival and productivity. Our study showed that the 3-d submergence duration had no effect on the survival (100%) of 21-day-old seedlings but survival percentage decreased to 97 and 65% at 7-d and 11-d submergence, respectively. Total chlorophyll, total soluble sugar, and starch concentrations also exhibited a similar pattern of decline. The activity of anti-oxidative defense enzymes (CAT, POX, SOD, and APX), recorded just after de-submergence was found to be 1.5-10-foldhigher than before submergence, increasing with the increase in the severity of stress. Additional post-flood application of K2O and N at 5-6 days after de-submergence led to the improvement in photosynthetic rate, yield attributes, and grain yield. An additional 10 kg each of N and K2O produced maximum 1000-grain weight and higher grain yield and harvest index. After submergence, the meta-analysis exhibited a significant reduction in total chlorophyll concentration due to increasing submergence duration, whereas the significantly higher activity of antioxidants was recorded irrespective of submergence duration. In association with the better anti-oxidative defense mechanism of Sub1 varieties, the additional doses of N and K2O at 5-d after de-submergence significantly enhanced the survival, post-flood recovery, and the rate of photosynthesis after de-submergence. These nutrient management options can provide an opportunity to explore the productivity potential of the SUB1-introgressed variety under natural flash-flood conditions, helping to cope with the existing problems in flood-prone areas. The findings of the study suggest that a proper time and method of N application with basal P can significantly contribute to higher rice yield in flash-flood prone areas.

Flood tolerance in two tree species that inhabit both the Amazonian floodplain and the dry Cerrado savanna of Brazil.

Comparing plants of the same species thriving in flooded and non-flooded ecosystems helps to clarify the interplay between natural selection, phenotypic plasticity and stress adaptation. We focussed on responses of seeds and seedlings of Genipa americana and Guazuma ulmifolia to substrate waterlogging or total submergence. Both species are commonly found in floodplain forests of Central Amazonia and in seasonally dry savannas of Central Brazil (Cerrado). Although seeds of Amazonian and Cerrado G. americana were similar in size, the germination percentage of Cerrado seeds was decreased by submergence (3 cm water) and increased in Amazonian seeds. The seeds of Amazonian G. ulmifolia were heavier than Cerrado seeds, but germination of both types was unaffected by submergence. Three-month-old Amazonian and Cerrado seedlings of both species survived 30 days of waterlogging or submersion despite suffering significant inhibition in biomass especially if submerged. Shoot elongation was also arrested. Submersion triggered chlorosis and leaf abscission in Amazonian and Cerrado G. ulmifolia while waterlogging did so only in Cerrado seedlings. During 30 days of re-exposure to non-flooded conditions, G. ulmifolia plants that lost their leaves produced a replacement flush. However, they attained only half the plant dry mass of non-flooded plants. Both submerged and waterlogged G. americana retained their leaves. Consequently, plant dry mass after 30 days recovery was less depressed by these stresses than in G. ulmifolia. Small amounts of cortical aerenchyma were found in roots 2 cm from the tip of well-drained plants. The amount was increased by flooding. Waterlogging but not submergence promoted hypertrophy of lenticels at the stem base of both species and adventitious rooting in G. ulmifolia. Despite some loss of performance in dryland plants, flood tolerance traits were present in wetland and dryland populations of both species. They are part of an overall stress-response potential that permits flexible acclimation to locally flooded conditions.

Willow species vary in elevational occurrence and morphological characteristics on the tidal freshwater section of the Elbe estuary

Willows are regarded as globally occurring pioneer species providing ecosystem functions like bank stabilization and water purification, and serving as shelterbelts to prevent degradation of the environment. Some species are adapted to physical disturbance like wind, waves and currents due to their fast growth and vigorous resprouting capacity, and are widely used in short rotation coppices for biofuel production. Knowledge on willow river floodplain-forest ecology exists and Salix flooding tolerance is documented. However, information on floodplain-forests along river mouths where the estuarine tide affects willows is scarce. In the Anthropocene, tidal amplitudes are increasing in many estuaries due to the deepening of the navigational channel for harbour accessibility. With regard to tidal forest restoration, the Elbe estuary close to the Hamburg harbour served as a model system to study the effect of increasing tidal flooding on Salix alba and Salix viminalis. Our results show occurrence of both species at sites up to 60cm below mean high water and their tolerance to twice daily flooding. Experimental findings on cuttings that were placed on flooding stairways at the tidal freshwater stretch showed the ability to resprout and grow up to more than 1m below mean high water for Salix viminalis but not for Salix alba. Willows may maintain their habitat when tidal amplitudes are increasing but repeated physical flood damage prevents Salix alba in tidal floodplain-forests from rejuvenation. These forests may be restored along protected sites to ensure the ecosystem functions and services they provide in the estuarine environment.

Characterization of the XTH Gene Family: New Insight to the Roles in Soybean Flooding Tolerance.

Xyloglucan endotransglycosylases/hydrolases (XTHs) are a class of enzymes involved in the construction and remodeling of cellulose/xyloglucan crosslinks and play an important role in regulating cell wall extensibility. However, little is known about this class of enzymes in soybean. Here, 61 soybean XTH genes (GmXTHs) were identified and classified into three subgroups through comparative phylogenetic analysis. Genome duplication greatly contributed to the expansion of GmXTH genes in soybean. A conserved amino acid motif responsible for the catalytic activity was identified in all GmXTHs. Further expression analysis revealed that most GmXTHs exhibited a distinct organ-specific expression pattern, and the expression level of many GmXTH genes was significantly associated with ethylene and flooding stress. To illustrate a possible role of XTH genes in regulating stress responses, the Arabidopsis AtXTH31 gene was overexpressed in soybean. The generated transgenic plants exhibited improved tolerance to flooding stress, with a higher germination rate and longer roots/hypocotyls during the seedling stage and vegetative growth stages. In summary, our combined bioinformatics and gene expression pattern analyses suggest that GmXTH genes play a role in regulating soybean stress responses. The enhanced soybean flooding tolerance resulting from the expression of an Arabidopsis XTH also supports the role of XTH genes in regulating plant flooding stress responses.

Light environment influences the flood tolerance in Cordia americana (L.) Gottschling & J.S.Mill.

The subtropical riverine forests present a variation in soil water availability throughout the year, following precipitation seasonality. The objective of this work was to evaluate the responses of Cordia americana to different light intensities combined with soil flooding. Seedlings were acclimated to light treatments, with full sun and shade conditions. Sun and shade plants were subjected to soil flooding during periods of 10 (short) and 30 (longer) days. After 10 days, flooded plants had a higher root dry mass accumulation and soluble sugars content, regardless of the light condition. Shade plants presented higher shoot soluble sugars content in relation to the sun plants. After 30 days, a higher shoot soluble sugar content was observed in sun and shade flooded plants. In addition, a higher root soluble sugar content was also observed in sun plants under flood. Periods of short flooding, characterized in subtropical forests as from 5 to 15 days, favor the growth of shade plants and the roots sugar accumulation, fact that can explain the species distribution. However, long periods of flooding may be associated with light environment plasticity, suggesting that the sun plants present a higher flooding tolerance, directly associated with the ability to maintain the sugar content.

Molecular and physiological responses in roots of two full-sib poplars uncover mechanisms that contribute to differences in partial submergence tolerance

Poplar is a major afforestation tree species in flood-prone areas. Here, we compared molecular and physiological responses in the roots of two full-sib poplar clones, LS1 (flood-tolerant) and LS2 (flood-susceptive), subjected to stagnant flooding using transcript and metabolite profiling. LS1 displayed less phenotypic damage and superior leaf gas exchange and plant growth compared with those of LS2. We concluded that three characteristics might contribute to the differences in flood tolerance between LS1 and LS2. First, fermentation was initiated through lactic dehydrogenation in LS1 roots under flooding and subsequently dominated by alcohol fermentation. However, lactic dehydrogenase was persistently active in flooded LS2. Second, 13 differentially expressed genes associated with energy and O2 consumption processes under soil flooding had lower transcript levels in LS1 than those in LS2, which might contribute to better energy-/O2-saving abilities and behaviours in flood-tolerant LS1 than those in flood-susceptible LS2 under hypoxic stress. Third, LS1 possessed increased reactive oxygen species scavenging abilities compared with those of LS2 under edaphic flooding. Our data are a valuable contribution to understanding the mechanisms involved in the flood tolerance of poplar.

Improving Flooding Tolerance of Crop Plants

A major problem of climate change is the increasing duration and frequency of heavy rainfall events. This leads to soil flooding that negatively affects plant growth, eventually leading to death of plants if the flooding persists for several days. Most crop plants are very sensitive to flooding, and dramatic yield losses occur due to flooding each year. This review summarizes recent progress and approaches to enhance crop resistance to flooding. Most experiments have been done on maize, barley, and soybean. Work on other crops such as wheat and rape has only started. The most promising traits that might enhance crop flooding tolerance are anatomical adaptations such as aerenchyma formation, the formation of a barrier against radial oxygen loss, and the growth of adventitious roots. Metabolic adaptations might be able to improve waterlogging tolerance as well, but more studies are needed in this direction. Reasonable approaches for future studies are quantitative trait locus (QTL) analyses or genome-wide association (GWA) studies in combination with specific tolerance traits that can be easily assessed. The usage of flooding-tolerant relatives or ancestral cultivars of the crop of interest in these experiments might enhance the chances of finding useful tolerance traits to be used in breeding.

Resilience of willows (Salix spp.) differs between families during and after flooding according to floodwater depth

Willows differ in their post-flooding responses according to floodwater depth and genotype. Although the morphological and physiological responses of willows to flooding have already been characterized, less is known about their responses during the post-flooding period. After the end of the stress episode, plants may modify some leaf and plant traits to compensate for biomass loss. The aim of this work was to analyze the post-flooding responses of different willow genotypes under two different depths of floodwater. The hypothesis was that the growth recovery in the post-flooding period would be different according to the genotype and the floodwater depth. We analyzed three genotypes of five willow families (four interspecific hybrids and one open-pollinated family). The treatments were: (1) Control: plants watered to field capacity; (2) T10: water covering 10 cm above soil level; (3) T65: water covering 65 cm above soil level. Both flooding treatments were followed by a period of recovery (without flooding). Growth was reduced by flooding in T65 but not in T10, while root-to-shoot ratio was reduced in both flooding treatments. The relative growth rate in height, leaf nitrogen concentration, stomatal conductance and electron transport rate changed in a different manner during the post-flooding period, depending on the treatment and genetic background. These results emphasize the need for evaluating a post-flooding recovery period for the breeding of willow genotypes destined for areas under risk of flooding. According to our results, Salix matsudana could be a source of flooding tolerance for willow breeding programs.

Separating effects of clonal integration on plant growth during submergence and de-submergence

Responses to both submergence and de-submergence are important for evaluating flood tolerance of plants. Clonal integration (resource translocation between connected ramets within clones) has been shown to increase flood tolerance of amphibious clonal plants. However, no study has truly separated the effects of clonal integration during de-submergence from those during submergence. We grew 40 clonal fragments of the amphibious plant species Alternanthera philoxeroides, each consisting of two ramet systems, under half-submerged conditions (one ramet system submerged and the other un-submerged) for 30 d and then de-submerged for 20 d. To evaluate the effects of clonal integration during submergence, stolon connection between the two ramet systems was either severed or not on day 1, and 10 replicates of the fragments of each treatment were harvested on day 30. To evaluate the effects of clonal integration after de-submergence, the remaining 20 clonal fragments with connected stolons during submergence were de-submerged; half of them were subjected to stolon severing on day 31 and the remaining 10 fragments were not. All the 20 fragments for de-submergence were harvested on day 50. After 30 d of submergence, stolon connection between the submerged and the un-submerged ramets significantly increased growth, biomass allocation to roots and photosynthetic capacities of the submerged ramets, and also increased growth and photosynthetic capacities of the un-submerged ramets. Consequently, clonal integration significantly increased growth of the apical ramets, the basal ramets and the whole fragments. However, after 20 d of de-submergence, stolon connection did not significantly affect growth or photosynthetic capacities of either de-submerged or un-submerged ramets. The results suggest that clonal integration plays different roles during submergence and de-submergence. It increases performance of submerged ramets during submergence by translocation of photosynthates from un-submerged ramets, but plays little roles during de-submergence.

Flooding tolerance of Sagittaria latifolia and Sagittaria rigida under controlled laboratory conditions

AbstractPool‐scale growing‐season water‐level reductions (drawdowns) have been implemented on the Upper Mississippi River in an effort to improve fish and wildlife habitat. Aquatic vegetation is a key habitat component, with perennial emergent species, such as Sagittaria latifolia and Sagittaria rigida, especially important. River managers have assumed the need for continuous drawdown during the growing season with limited reflooding and used this guidance in assessing the potential for an ecologically successful drawdown. However, information on the effects of growing‐season flooding episodes on survival and growth of Sagittaria is limited. To assess the flooding tolerance of S. latifolia and S. rigida, we evaluated multiple levels of timing, duration, and depth on survival and productivity of plants. Plants were produced from S. latifolia and S. rigida seeds and S. latifolia tubers; all were reared under moist‐soil or shallow‐flooded rearing conditions. Mortality of plants was low (2%) among plants from large tubers, low (7%) among seedlings (and largely associated with early flooding treatments), and modest (11%) among plants from small tubers (with no clear effects of inundation). Flooding treatments generally had a positive effect on biomass production from seedlings, particularly when treatments occurred early, were relatively shallow, and were short in duration. There were no clear effects of depth, duration, or timing components of flooding treatments on plant biomass arising from tubers. This experiment indicates that S. latifolia and S. rigida are relatively tolerant of flooding events during the growing season and may actually benefit from some level of inundation.

Positive role of 1-aminocyclopropane-1-carboxylate deaminase-producing endophytic Streptomyces sp. GMKU 336 on flooding resistance of mung bean

Previously, a plant growth-promoting endophytic Streptomyces sp., namely GMKU 336, has been shown to improve salt tolerance in rice through the action of 1-aminocyclopropane-1-carboxylate deaminase (ACCD) by converting a precursor of ethylene, (ACC) in plants into ammonia and α-ketobutyrate and consequently reducing the ethylene level. In this study, strain GMKU 336 and its ACCD-deficient mutant were further investigated regarding flooding tolerance in mung bean CN72 [Vigna radiata (L.) Wilczek cv. CN72]. The results clearly demonstrated that mung bean associated with Streptomyces sp. GMKU 336 significantly increased plant elongation and biomass, chlorophyll content, leaf area, leaf color and adventitious roots, and reduced the ethylene level under flooding conditions when compared to un-inoculated plants and those inoculated with the ACCD-deficient mutant. It was concluded that ACCD-producing Streptomyces sp. GMKU 336 that beneficially improved salt tolerance in rice also enhanced flooding tolerance in mung bean via the action of ACCD.

Early-Season Soil Waterlogging and N Fertilizer Sources Impacts on Corn N Uptake and Apparent N Recovery Efficiency

Soil waterlogging resulting from extreme precipitation events creates anaerobic conditions that may inhibit plant growth and increase N losses. A three-year (2013–2015) field experiment was conducted in poorly-drained claypan soils to assess the effects of waterlogging [0 or 7-days waterlogging at V3 growth stage of corn (Zea mays L.)] and pre-plant application of different N fertilizer sources and post-waterlogging rescue N application (0 or 84 kg N ha−1 of urea plus urease inhibitor (NCU + UI) at V7) on chlorophyll SPAD meter (CM) readings, stomatal conductance, ear leaf and silage N concentrations, N uptake and apparent N recovery efficiency (ARE) of two corn hybrids with varying amounts of flood tolerance. Pre-plant N fertilizer sources included a non-treated control (CO), urea (NCU), urea plus nitrification inhibitor (NCU + NI) and polymer coated urea (PCU) applied at 168 kg N ha−1. In 7-days waterlogged plots, rescue N applications increased N uptake in PCU treatments 33% and 40% in 2013 and 2014, respectively, as well as in NCU by 48% in 2013. In 7-days waterlogged plots which received rescue N applications, NCU and PCU in 2013 resulted in higher N uptake than CO and NCU + NI by 47 to 77 kg ha−1. PCU had higher N uptake than NCU and NCU + NI by 78 and 72 kg ha−1 in 7-days waterlogged plots that received rescue N applications in 2014. Corn hybrid showed no differences in N uptake and ARE in our study. Our results indicate combining pre-plant N fertilizer source selection and rescue N applications may be a strategy to reduce possible decreases in corn N uptake caused by early season soil waterlogging in average rainfall years.

Interaction between depth and duration matters: flooding tolerance of 12 floodplain meadow species

In riparian landscapes, regular flooding plays a crucial role in the distribution and diversity of plant species. Particularly in floodplain grassland, the microrelief, which is often the result of riverine sedimentation through flooding, leads to differing flooding depths and durations on a microscale, with little-known impacts on plants. Here, we aim to reveal the effects of flooding duration and flooding depth, as well as their interaction, on seedlings of 12 floodplain meadow plant species. To this end, we performed flooding procedures for 2 and 4 weeks with no, partial, and complete submergence using seedlings of floodplain meadow species in six familial pairs with a preference for relatively wetter or drier microhabitats. We show that an increased flooding duration and flooding depth negatively affect the performance of seedlings. The interactive effect of these two factors appears to play an essential role in the flooding tolerance of plant species. In conclusion, our results suggest that the studied factors and their interaction have high importance in determining the flooding tolerance of floodplain meadow plant species. Despite its crucial function, the effect of the depth × duration interaction seems to be underestimated in experimental studies focusing on flooding effects in plants. Thus, this interaction, as well as its combination with other factors, should be studied in more detail to further understand plant responses to flooding events.

Functional characterization of 1-aminocyclopropane-1-carboxylic acid oxidase gene in Arabidopsis thaliana and its potential in providing flood tolerance

Ethylene is a phytohormone that has gained importance through its role in stress tolerance and fruit ripening. In our study we evaluated the functional potential of the enzyme involved in ethylene biosynthesis of plants called ACC (aminocyclopropane-1-carboxylic acid) oxidase which converts precursor ACC to ethylene. Studies on ethylene have proven that it is effective in improving the flood tolerance in plants. Thus our goal was to understand the potential of ACC oxidase gene overexpression in providing flood tolerance in transgenic plants. ACC oxidase gene was PCR amplified and inserted into the pBINmgfp5-er vector, under the control of a constitutive Cauliflower Mosaic Virus promoter. GV101 strain of Agrobacterium tumefaciens containing recombinant pBINmgfp5-er vector (referred herein as pBIN-ACC) was used for plant transformation by the ‘floral dip’ method. The transformants were identified through kanamycin selection and grown till T3 (third transgenic) generation. The flood tolerance was assessed by placing both control and transgenic plants on deep plastic trays filled with tap water that covered the soil surface. Our result shows that wild-type Arabidopsis could not survive more than 20 days under flooding while the transgenic lines survived 35 days, suggesting development of flood tolerance with overexpression of ACC oxidase. Further molecular studies should be done to elucidate the role and pathways of ACC oxidase and other phytohormones involved in the development of flood adaptation.

A stress recovery signaling network for enhanced flooding tolerance in Arabidopsis thaliana

Abiotic stresses in plants are often transient, and the recovery phase following stress removal is critical. Flooding, a major abiotic stress that negatively impacts plant biodiversity and agriculture, is a sequential stress where tolerance is strongly dependent on viability underwater and during the postflooding period. Here we show that in Arabidopsis thaliana accessions (Bay-0 and Lp2-6), different rates of submergence recovery correlate with submergence tolerance and fecundity. A genome-wide assessment of ribosome-associated transcripts in Bay-0 and Lp2-6 revealed a signaling network regulating recovery processes. Differential recovery between the accessions was related to the activity of three genes: RESPIRATORY BURST OXIDASE HOMOLOG D, SENESCENCE-ASSOCIATED GENE113, and ORESARA1, which function in a regulatory network involving a reactive oxygen species (ROS) burst upon desubmergence and the hormones abscisic acid and ethylene. This regulatory module controls ROS homeostasis, stomatal aperture, and chlorophyll degradation during submergence recovery. This work uncovers a signaling network that regulates recovery processes following flooding to hasten the return to prestress homeostasis.

Genetic Analysis of Flooding Tolerance in an Andean Diversity Panel of Dry Bean (Phaseolus vulgaris L.).

Climate change models predict temporal and spatial shifts in precipitation resulting in more frequent incidents of flooding, particularly in regions with poor soil drainage. In these flooding conditions, crop losses are inevitable due to exposure of plants to hypoxia and the spread of root rot diseases. Improving the tolerance of bean cultivars to flooding is crucial to minimize crop losses. In this experiment, we evaluated the phenotypic responses of 277 genotypes from the Andean Diversity Panel to flooding at germination and seedling stages. A randomized complete block design, with a split plot arrangement, was employed for phenotyping germination rate, total weight, shoot weight, root weight, hypocotyl length, SPAD index, adventitious root rate, and survival score. A subset of genotypes (n = 20) were further evaluated under field conditions to assess correlations between field and greenhouse data and to identify the most tolerant genotypes. A genome-wide association study (GWAS) was performed using ~203 K SNP markers to understand the genetic architecture of flooding tolerance in this panel. Survival scores between field and greenhouse data were significantly correlated (r = 0.55, P = 0.01). Subsequently, a subset of the most tolerant and susceptible genotypes were evaluated under pathogenic Pythium spp. pressure. This experiment revealed a potential link between flooding tolerance and Pythium spp. resistance. Several tolerant genotypes were identified that could be used as donor parents in breeding pipelines, especially ADP-429 and ADP-604. Based on the population structure analysis, a subpopulation consisting of 20 genotypes from the Middle American gene pool was detected that also possessed the highest root weight, hypocotyl length, and adventitious root development under flooding conditions. Genomic regions associated with flooding tolerance were identified including a region on Pv08/3.2 Mb, which is associated with germination rate and resides in vicinity of SnRK1.1, a central gene involved in response of plants to hypoxia. Furthermore, a QTL at Pv07/4.7 Mb was detected that controls survival score of seedlings under flooding conditions. The association of these QTL with the survivability traits including germination rate and survival score, indicates that these loci can be used in marker-assisted selection breeding to improve flooding tolerance in the Andean germplasm.

An Integrated Approach of Proteomics and Computational Genetic Modification Effectiveness Analysis to Uncover the Mechanisms of Flood Tolerance in Soybeans.

Flooding negatively affects the growth of soybeans. Recently, omic approaches have been used to study abiotic stress responses in plants. To explore flood-tolerant genes in soybeans, an integrated approach of proteomics and computational genetic modification effectiveness analysis was applied to the soybean (Glycine max L. (Merrill)). Flood-tolerant mutant and abscisic acid (ABA)-treated soybean plants were used as the flood-tolerant materials. Among the primary metabolism, glycolysis, fermentation, and tricarboxylic acid cycle were markedly affected under flooding. Fifteen proteins, which were related to the affected processes, displayed similar protein profiles in the mutant and ABA-treated soybean plants. Protein levels of glyceraldehyde-3-phosphate dehydrogenase (GAPDH), aconitase 1, and 2-oxoglutarate dehydrogenase were higher in flood-tolerant materials than in wild-type soybean plants under flood conditions. These three proteins were positioned in each of the three enzyme groups revealed by our computational genetic modification effectiveness analysis, and the three proteins configured a candidate set of genes to promote flood tolerance. Additionally, transcript levels of GAPDH were similar in flood-tolerant materials and in unstressed plants. These results suggest that proteins related to energy metabolism might play an essential role to confer flood tolerance in soybeans.

Natural variation in the promoter of rice calcineurin B-like protein10 (OsCBL10) affects flooding tolerance during seed germination among rice subspecies.

Rice (Oryza sativa L.) has two ecotypes, upland and lowland rice, that have been observed to show different tolerance levels under flooding stress. In this study, two rice cultivars, upland (Up221, flooding-intolerant) and lowland (Low88, flooding-tolerant), were initially used to study their molecular mechanisms in response to flooding germination. We observed that variations in the OsCBL10 promoter sequences in these two cultivars might contribute to this divergence in flooding tolerance. Further analysis using another eight rice cultivars revealed that the OsCBL10 promoter could be classified as either a flooding-tolerant type (T-type) or a flooding-intolerant type (I-type). The OsCBL10 T-type promoter only existed in japonica lowland cultivars, whereas the OsCBL10 I-type promoter existed in japonica upland, indica upland and indica lowland cultivars. Flooding-tolerant rice cultivars containing the OsCBL10 T-type promoter have shown lower Ca2+ flow and higher α-amylase activities in comparison to those in flooding-intolerant cultivars. Furthermore, the OsCBL10 overexpression lines were sensitive to both flooding and hypoxic treatments during rice germination with enhanced Ca2+ flow in comparison to wild-type. Subsequent findings also indicate that OsCBL10 may affect OsCIPK15 protein abundance and its downstream pathways. In summary, our results suggest that the adaptation to flooding stress during rice germination is associated with two different OsCBL10 promoters, which in turn affect OsCBL10 expression in different cultivars and negatively affect OsCIPK15 protein accumulation and its downstream cascade.