Waterlogging Treatment Research Articles

Enhancement of Waterlogging Tolerance and Improvement of Grain Quality in Waxy Maize With Exogenous EDAH: A Mixture of Ethephon and Diethyl Aminoethyl Hexanoate

ABSTRACTGlobal warming has led to more frequent extreme weather events, such as heavy summer rains, in the Huang‐Huai‐Hai region. These events significantly impede the growth and development of waxy maize in the area and disrupt the stable progression of the industry. However, there is a lack of effective agricultural measures to mitigate the impact of waterlogging, and the underlying regulation mechanisms remain unclear. To fill this knowledge gap, we conducted a two‐year experiment to assess whether exogenous EDAH (a mixture of ethephon and diethyl aminoethyl hexanoate (DA‐6), ethephon: DA‐6 = 27%: 3%) application during the waxy maize V6 stage, combined with 10 days of waterlogging treatment at the V6, VT and R2 growth stages. The results indicate that exogenous EDAH mitigates the adverse effects of waterlogging stress to a certain extent. It is noteworthy that exogenous EDAH increases the leaf area index and photosynthetic parameters of waxy maize, enhances the activity of catalase in ear leaves at the R3 stage, inhibits the accumulation of malondialdehyde and delays premature aging of plants. Furthermore, exogenous EDAH delays premature ripening of grains caused by waterlogging, increases the moisture content of fresh waxy maize grains during the fresh edible period, but does not effectively mitigate the yield losses caused by waterlogging. However, exogenous EDAH effectively improves grain quality under waterlogging stress, increasing the soluble sugar content and total protein content while reducing starch content, ultimately enhancing the edibility of fresh ears. Through TOPSIS comprehensive evaluation, it can be inferred that exogenous EDAH effectively mitigates the overall impact of waterlogging on waxy maize at both the V6 and VT stages. This research sheds light on potential strategies to mitigate the adverse effects of waterlogging on agricultural productivity and grain quality.

Foliar-applied sulfur is supplemental to soil application in alleviating waterlogging stress through the mitigation of oxidative stress and ion homeostasis in rapeseed (Brassica napus L.)

Waterlogging has appeared as a major issue for agricultural production and has an adverse effect on rapeseed growth. A pot experiment was conducted to investigate the effect of soil and/or foliar applied S in alleviating the waterlogging stress in rapeseed (Brassica napus L. cv. Campino). The experiment treatments included, no soil S application (-SS), soil S fertilization (SS, 70 mg S kg−1 soil as MgSO4), foliar S application (FS, 300 ppm MgSO4) and both soil and foliar application of S (SS+FS). All the treatments were subjected to normal soil water (control) and waterlogged condition. Foliar S was applied two days prior to the onset of waterlogging treatment, which was imposed at vegetative stage (BBCH-31) for 7 days. The results demonstrated that without foliar S application, both unfertilized (-S) and S-fertilized (+S) waterlogged plants showed elevated level of hydrogen peroxide (35 % and 15 %) and malondialdehyde (84 % and 101 %) and reduced nutrients uptake, net photosynthesis and plant growth compared to their non-waterlogged counterparts. Although all S treatments alleviated the suppressing effects of waterlogging stress, the alleviative effect of soil plus foliar applied S was higher than these individual treatments. It increased dry matter by 17 %, superoxide dismutase activity by 15 %, catalase activity by 15 %, glutathione reductase activity by 14 %, ascorbate peroxidase activity by 18 %, ascorbate content by 19 %, glutathione content by 28 %. The increase in the growth and antioxidant activities of the soil plus foliar S supplemented plants was attributed to the increase in the contents of some nutrients (S 8 %, P 18 %, Mg 9 %, Zn 13 %) and net photosynthesis rate (19 %), whereas decrease in hydrogen peroxide (15 %), malondialdehyde (20 %), oxidized glutathione content (9 %), dehydroascorbic acid content (5 %) compared with untreated (without foliar-S) waterlogged plants. Collectively, the study concludes that foliar-S application supplements soil S fertilization in alleviating waterlogging stress in rapeseed plants, through inducing physiological and biochemical resistance, and improving homeostasis as well.

Exogenous application of melatonin attenuates waterlogging stress through adopting quiescence adaptation technique in tomato seedlings

Waterlogging (WL) is a major limiting factor in global crop production and seriously limits growth and yield improvement in low-lying rainfed regions. Melatonin (MT) is a vital phytohormone that functions as a "master regulator" in multiple facets related to plant growth and development, in addition to maintaining a potential role in response to stresses. However, the pharmacological role of MT in attenuating waterlogging stress in tomato largely remains elucidated. The objective of the current investigation is to justify the physiological regulatory mechanism of tomato seedlings exposed to WL and the putative functions of MT to mitigate the adverse effects of WL. Tomato seedlings were grown on substrate (peat: vermiculite, 2:1, v/v) and at the 4th leaf stage subjected to waterlogging stress for 10 days and seedlings were foliar sprayed with melatonin during waterlogging stress. The results revealed that WL significantly arrested tomato seedlings growth, and reduced pigment content coincided with enhanced leaf senescence. MT supplementation attenuated WL-induced oxidative damage through increasing osmoprotectants activity, elevating antioxidant enzyme functioning synchronized with inhibiting excess reactive oxygen species (ROS) production. The concentrations of MT (28 %), abscisic acid (ABA, 170 %), and 1-aminocyclopropane-1-carboxylic acid (ACC, 129 %) were increased, while indole acetic acid (IAA, 15 %), jasmonic acid (JA, 55 %) and gibberellic acid (GA3, 26 %) content were decreased in only WL seedlings roots relative to control seedlings. The core anaerobic respiration enzyme alcohol dehydrogenase (ADH) and pyruvate decarboxylase (PDC) activity were elevated by 127 % and 163 %, respectively at day 10 in WL+MT received seedlings than control. WL treatment varyingly contributed on nutrient content, as evidenced that N+, K+, and Ca2+ content decreased, whereas Mn2+, Fe2+, and Mg2+ content increased and MT addition reversed their concentrations under similar stress conditions. Exogenous MT promoted WL-tolerance of tomato by positively suppressing respiratory burst oxidase homologs (RBOH)-regulating gene expression while up-regulating ethylene biosynthesis gene transcription. Most importantly, programmed cell death (PCD) regulated enzyme caspase-3 activity concurred with PCD-induced gene (caspase-3, pirin, TBN1) expression significantly inhibited by MT application. In general, these findings reveal that external supplementation with MT can improve plant tolerance to WL through complex processes and multifaceted mechanisms.

Effects of Waterlogging Stress on Root Growth and Soil Nutrient Loss of Winter Wheat at Seedling Stage

With global climate change, flooding events are becoming more frequent. However, the mechanism of how waterlogging stress affects crop roots needs to be studied in depth. Waterlogging stress can also lead to soil nitrogen and phosphorus loss, resulting in agricultural surface pollution. The aim of this study is to clarify the relationship between soil nitrogen and phosphorus distribution, root growth characteristics, and nitrogen and phosphorus loss in runoff water under waterlogging stress during the winter wheat seedling stage. In this paper, Zhengmai 136 was selected as the experimental material, and two water management methods (waterlogging treatment and non-waterlogging control treatment) were set up. Field experiments were conducted at the Wudaogou Hydrological Experimental Station in 2022 to assess the nitrogen and phosphorus concentrations in runoff water under waterlogging stress. The study also aimed to analyze the nitrogen and phosphorus content and the root distribution characteristics in different soil layers under waterlogging stress. The results showed as the following: 1. Waterlogging stress increased the characteristic parameters of winter wheat roots in both horizontal and vertical directions. Compared with the control treatment, the root length increased by 1.2–29.9% in the waterlogging treatment, while the root surface area and volume increased by an average of 3.1% and 41.9%, respectively. 2. Nitrogen and phosphorus contents in waterlogged soils were enriched in the 0–20 cm soil layer, but both tended to decrease in the 20–60 cm soil layer. Additionally, there was an inverse relationship between the distribution of soil nutrients and the distribution of wheat roots. 3. During the seedling stage of winter wheat, nitrogen loss was the main factor in the runoff water. In addition, nitrate nitrogen concentration averaged 55.2% of the total nitrogen concentration, while soluble phosphorus concentration averaged 79.1% of the total phosphorus concentration. 4. The results of redundancy analysis demonstrated that available phosphorus in the soil was the key environmental factor affecting the water quality of runoff water. Total phosphorus and dissolved phosphorus in the water were identified as the dominant factors influencing root growth.

Tomato (Solanum lycopersicum L.) YTH Domain-Containing RNA-Binding Protein (YTP) Family Members Participate in Low-Temperature Treatment and Waterlogging Stress Responses

YT521-B homology (YTH) domain-containing RNA-binding proteins (YTPs) are important N6-methyladenosine (m6A) readers that have crucial roles in determining the destiny of m6A-modified RNAs, which are the most widespread RNA modifications in eukaryotes. Tomatoes (Solanum lycopersicum L.) hold significant importance in both dietary consumption patterns and scientific inquiries. While the YTP gene family has been characterized in tomatoes, their specific reactions to the low temperature and waterlogging stresses remain to be elucidated. In our study, nine tomato SlYTPs could be divided into five subclasses, YTHDFa-c and YTHDCa-b. After gene cloning and measuring their expression levels under stress conditions, it was revealed that SlYTP8 exhibited increased sensitivity to low-temperature treatment, while the expression levels of SlYTP9 were notably upregulated in leaf tissues subjected to waterlogging conditions. As members of the YTHDFc subfamily, SlYTP8 and SlYTP9 are both localized in the cytoplasm. Nevertheless, overexpression (OE) of SlYTP8 increased the sensitivity of tomato plants to low-temperature treatment, which was manifested by a higher accumulation of malondialdehyde (MDA) and hydrogen peroxide (H2O2) and a weaker reactive oxygen species scavenging ability compared to wild-type (WT) tomatoes. However, in comparison to WT plants, the leaves of SlYTP9 OE tomatoes showed higher chlorophyll content and a stronger reactive oxygen species scavenging ability after 3 days of waterlogging treatment, thereby increasing the resistance of tomatoes to waterlogging stress. Moreover, in order to investigate the possible molecular mechanisms underlying their responses to the low temperature and waterlogging stresses, the transcription factors and interacting protein networks associated with SlYTP8/9 promoters and proteins were also predicted, respectively. These results could fill the gap in the understanding of tomato YTPs in response to the low temperature and waterlogging stresses, while also providing a theoretical and experimental basis for subsequent studies on their molecular mechanisms.

Transcriptome and metabolome analyses reveal molecular insights into waterlogging tolerance in Barley

Waterlogging stress is one of the major abiotic stresses affecting the productivity and quality of many crops worldwide. However, the mechanisms of waterlogging tolerance are still elusive in barley. In this study, we identify key differentially expressed genes (DEGs) and differential metabolites (DM) that mediate distinct waterlogging tolerance strategies in leaf and root of two barley varieties with contrasting waterlogging tolerance under different waterlogging treatments. Transcriptome profiling revealed that the response of roots was more distinct than that of leaves in both varieties, in which the number of downregulated genes in roots was 7.41-fold higher than that in leaves of waterlogging sensitive variety after 72 h of waterlogging stress. We also found the number of waterlogging stress-induced upregulated DEGs in the waterlogging tolerant variety was higher than that of the waterlogging sensitive variety in both leaves and roots in 1 h and 72 h treatment. This suggested the waterlogging tolerant variety may respond more quickly to waterlogging stress. Meanwhile, phenylpropanoid biosynthesis pathway was identified to play critical roles in waterlogging tolerant variety by improving cell wall biogenesis and peroxidase activity through DEGs such as Peroxidase (PERs) and Cinnamoyl-CoA reductases (CCRs) to improve resistance to waterlogging. Based on metabolomic and transcriptomic analysis, we found the waterlogging tolerant variety can better alleviate the energy deficiency via higher sugar content, reduced lactate accumulation, and improved ethanol fermentation activity compared to the waterlogging sensitive variety. In summary, our results provide waterlogging tolerance strategies in barley to guide the development of elite genetic resources towards waterlogging-tolerant crop varieties.

Physiological and biochemical response analysis of Styrax tonkinensis seedlings to waterlogging stress

Climate change is increasing flooding in provinces of the south of the Yangtze River, posing challenges for promoting Styrax tonkinensis seedlings in these areas. To understand the physiological reasons for this species' intolerance to waterlogging, we observed biochemical parameters in one-year-old S. tonkinensis seedlings during two seasons. For 4 and 12 days in summer and winter experiments, respectively, we subjected seedlings to a pot-in-pot waterlogging treatment. Control groups were established at 0 h and 0 days. We examined indicators related to root vigor, reactive oxygen species (ROS), antioxidant enzymes, fermentative pathways, and more. The results displayed that decreased abscisic acid accumulation in roots inhibited water transport. Increased dehydrogenase and lactate dehydrogenase activity in roots promoted alcohol and lactate fermentation, causing toxic damage and reduced root vigor, impeding water absorption. In leaves, high ROS levels led to lipid peroxidation, exacerbating water loss from continuous transpiration. The high relative electric conductivity and low leaf relative water content indicated water loss, causing leaf wilting and shriveling. Conversely, winter seedlings, devoid of leaves, significantly reduced transpiration, and dormancy delayed root fermentation. With less ROS damage in roots, winter seedlings exhibited greater waterlogging tolerance. In summary, excessive water loss from leaves and inhibited vertical water transport contributed to low summer survival rates, while winter leafless dormancy and reduced ROS damage enhanced tolerance. Our findings provide insights for enhancing waterlogging resistance in S. tonkinensis amidst climate change challenges.

Transcriptome analysis of waterlogging-induced adventitious root and control taproot of Mentha arvensis.

The present study reports differentially expressed transcripts in the waterlogging-induced adventitious root (AR) of Mentha arvensis; the identified transcripts will help to understand AR development and improve waterlogging stress response. Waterlogging notably hampers plant growth in areas facing waterlogged soil conditions. In our previous findings, Mentha arvensis was shown to adapt better in waterlogging conditions by initiating the early onset of adventitious root development. In the present study, we compared the transcriptome analysis of adventitious root induced after the waterlogging treatment with the control taproot. The biochemical parameters of total carbohydrate, total protein content, nitric oxide (NO) scavenging activity and antioxidant enzymes, such as catalase activity (CAT) and superoxide dismutase (SOD) activity, were enhanced in the adventitious root compared with control taproot. Analysis of differentially expressed genes (DEGs) in adventitious root compared with the control taproot were grouped into four functional categories, i.e., carbohydrate metabolism, antioxidant activity, hormonal regulation, and transcription factors that could be majorly involved in the development of adventitious roots. Differential expression of the upregulated and uniquely expressing thirty-five transcripts in adventitious roots was validated using qRT-PCR. This study has generated the resource of differentially and uniquely expressing transcripts in the waterlogging-induced adventitious roots. Further functional characterization of these transcripts will be helpful to understand the development of adventitious roots, leading to the resistance towards waterlogging stress in Mentha arvensis.

Differences of waterlogging tolerance in winter pulse crop between emergence and vegetative stages

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

Waterlogging Hardening Effect on Transplant Stress Tolerance in Pinus densiflora

Waterlogging induces oxidative damage by accumulation of reactive oxygen species due to stomatal closure. Plants alter their physiological and molecular mechanisms to reduce and adapt to oxidative stress. This mechanism of adaptation to stress, known as hardening, can support future stress tolerance. Pinus densiflora seedlings were grown under waterlogging treatment for three years and then transplanted to another site to identify the waterlogging hardening effect on transplanting. Transcriptome analysis was conducted before and after transplanting, and physiological factors were measured after transplanting. After transplanting, wounding stress is the main cause of transplant stress, and 13 genes related to phenylpropanoid were upregulated for the recovery of wounded roots in waterlogged hardened seedlings. The leaf starch and soluble sugar content of the waterlogged hardened seedlings were 50.3% and 40.5% lower due to the formation of cell walls. However, auxin-related genes were downregulated in waterlogging hardened seedlings, resulting in a lower tendency for height growth in hardened waterlogged seedlings. Waterlogging hardening mitigated transplant stress by wounding more than non-hardening, whereas waterlogging hardening may negatively affect seedling height. Our study provides evidence for the hardening effect of long-term waterlogging on transplanted P. densiflora seedlings.

Polyamine Alterations of Triticale in Response to Herbicide, Drought and Waterlogging Treatments

Drought and waterlogging are environmental stress factors that havoc normal plant growth and development. Polyamines are plant growth regulators, which participate in plant growth and development, as well as in the physiological responses to stress conditions. The polyamines fractions were evaluated in triticale plants pretreated with the selective herbicide Serrate®, and exposed to drought or waterlogging for 7 days. The herbicide applied alone provoked a slight decrease in polyamine content. A decrease of polyamine content was found also after drought, while waterlogging provoked an increase in polyamine levels. These data correlate with plant fitness and phenotype characteristics of treated seedlings. Our data provide new information about the role of plant polyamines in the physiological responses of triticale plants to water stress after herbicide application.

Effect of waterlogging on photosynthesis and growth of finger millet (Eleusine coracana)

AbstractFinger millet (Eleusine coracana (L.) Gaertn.) is an important cereal crop grown in most parts of Asia and Africa owing to its ability to adapt to stressful environments. The objective of this study was to examine the effect of waterlogging on photosynthesis and growth of finger millet. Plants were subjected to waterlogging by keeping pots filled with water from June 16 (transplanting) until November 12 (harvesting) in 2021 in Tokyo. After being subject to 13 days of waterlogging, net photosynthetic rate (Pn) decreased by 10.1% due to reduced stomatal conductance (gs), transpiration rate, and relative chlorophyll content (SPAD). From July to September, long‐term waterlogging increased Pn in the range of 4.9%–26.3%. The alleviation of high temperature, increase in SPAD and gs, and other nonstomatal components were implicated as the cause of increased Pn in summer. These findings suggest that the effect of waterlogging on photosynthesis varies with the duration of waterlogging or the growing season. Plant height was significantly reduced by 27.9% during the first 13 days of waterlogging and remained lower throughout the waterlogging treatment than in irrigated conditions. Waterlogging also caused other morphological changes, such as a significant increase in the number of tillers (63.2%) and a 16.7% increase in the number of panicles. Grain yield decreased by 13.6%, but the reduction was not significant. Overall, finger millet has the potential to tolerate waterlogging and is a promising crop for both paddy and field farming.

Photosynthetic adaptation mechanisms of waterlogged wheat (Triticum aestivum) at flowering under exogenous nitric oxide donor application

AbstractThe effects of nitric oxide (NO) on the photosynthetic adaptation mechanisms of wheat plants in waterlogging during the flowering stage are poorly understood. Field and pot experiments using two cultivars were conducted with three treatments: waterlogging (WL), waterlogging plus NO donor sodium nitroprusside (WLsnp), and adequate water (CK). The results indicated that the WLsnp and CK treatments exhibited significantly higher 1000‐kernel weight and yield than the WL treatment because of high photosynthetic potential(P<0.05). We found that the photosynthetic performance, including photosynthetic rate (Pn), stomatal conductance (gs), mesophyll conductance (gm), carbon dioxide concentration at the carboxylation site (Cc), maximum carboxylation rate (Vcmax), maximum electron transfer rate (Jmax), actual electron transfer rate (J), actual PSII efficiency (ΦPSII) and potential maximum efficiency in PSII (Fv/Fm), was significantly improved in the WLsnp treatment compared to the WL treatment, both during waterlogging and after de‐waterlogging. Little difference was observed in the photosynthetic performance between the WLsnp and CK treatments during waterlogging for cultivar YM15 and after de‐waterlogging for cultivar YM24. Further analysis indicated that gs, gm and J were identified as key physiological indicators that synergistically regulate Pn of waterlogged wheat plants. Overall, the improvement of wheat's waterlogging resistance capacity after spraying NO is mainly related to high gs, great gm, and high J.

Varietal Differences in Wet Damage of Broccoli (Brassica oleracea L. var. italica) Under Waterlogging Conditions

Abstract Broccoli is a typical wet-sensitive vegetable. Precipitation levels in Japan have been unusually high recently, so the wet tolerance of broccoli is of great interest to farmers. The purpose of this study is to gather basic information to help with broccoli cultivation in unusually wet conditions by investigating the varying responses of different cultivars to wet conditions. In two-year pot experiments, the early stage of broccoli growth was compared using on cultivars that exhibit unique characteristics in terms of tolerance to wet conditions, and differences in yield were also confirmed during the harvest season in a field experiment. Broccoli plants subjected to three days of waterlogging treatment exhibited wilting, yellowing and reduced biomass. Significant interactions between treatment and cultivar were also detected for biomass, water content, and photosynthetic ability. The ‘Shigemori’ cultivar showed less susceptibility to wet damage compared to the other cultivars. The trend could be observed in the head yield in the field experiment. The unique cultivars shown in this study may be helpful in broccoli cultivation and may be suitable for use as parent material in breeding. Furthermore, a short-term pot experiment can help evaluate broccoli wet tolerance during the early growth.

Physiological, Epigenetic, and Transcriptome Analyses Provide Insights into the Responses of Wheat Seedling Leaves to Different Water Depths under Flooding Conditions

Flooding stress, including waterlogging and submergence, is one of the major abiotic stresses that seriously affects the growth and development of plants. In the present study, physiological, epigenetic, and transcriptomic analyses were performed in wheat seedling leaves under waterlogging (WL), half submergence (HS), and full submergence (FS) treatments. The results demonstrate that FS increased the leaves’ hydrogen peroxide (H2O2) and malondialdehyde (MDA) contents and reduced their chlorophyll contents (SPAD), photosynthetic efficiency (Fv/Fm), and shoot dry weight more than HS and WL. In addition, FS increased catalase (CAT) and peroxidase (POD) activities more than HS and WL. However, there were no significant differences in the contents of H2O2, MDA, SPAD, and Fv/Fm, and the activities of superoxide dismutase (SOD) and POD between the HS and WL treatments. The changes in DNA methylation were related to stress types, increasing under the WL and HS treatments and decreasing under the FS treatment. Additionally, a total of 9996, 10,619, and 24,949 genes were differentially expressed under the WL, HS, and FS treatments, respectively, among which the ‘photosynthesis’, ‘phenylpropanoid biosynthesis’, and ‘plant hormone signal transduction’ pathways were extensively enriched under the three flooding treatments. The genes involved in these pathways showed flooding-type-specific expression. Moreover, flooding-type-specific responses were observed in the three conditions, including the enrichment of specific TFs and response pathways. These results will contribute to a better understanding of the molecular mechanisms underlying the responses of wheat seedling leaves to flooding stress and provide valuable genetic and epigenetic information for breeding flood-tolerant varieties of wheat.

Root-associated symbiotic fungi enhance waterlogging tolerance of peach seedlings by increasing flavonoids and activities and gene expression of antioxidant enzymes

Root-associated symbiotic fungi can enhance the host plant’s ability to tolerate adverse environmental conditions, but it’s unclear whether and how they enhance waterlogged peach plants. This study aimed to investigate the effects of Funneliformis mosseae (Fm), an arbuscular mycorrhizal fungus, and Serendipita indica (Si), an endophytic fungus, on plant growth, root development, reactive oxygen species (ROS) levels, total flavonoids, ROS scavenging activity of flavonoids, and activities and gene expression of antioxidant enzymes in roots of waterlogged peach seedlings. Although waterlogging treatment had little effect on root development, Fm and Si, particularly Fm, improved root development variables to varying degrees. Waterlogging significantly promoted superoxide anion radicals (O2•−) and hydrogen peroxide (H2O2) levels, whereas Fm and Si distinctly reduced O2•− and H2O2 levels under waterlogging. Waterlogging triggered an increase in total flavonoids in fungi-inoculated seedlings, and the two fungi also significantly increased total flavonoid concentrations and the scavenging activity of total flavonoids to hydroxyl radical, O2•−, and 2,2-diphenyl-1-picrylhydrazyl radical. In addition, root fungal colonization rate was negatively and significantly correlated with O2•− and H2O2, but positively with total flavonoids. Under waterlogging conditions, Fm significantly raised root superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPX) activities, and Si likewise elevated root SOD, CAT, GPX, and peroxidase (POD) activities, compared with uninoculated treatment. Although the expression of various antioxidant enzyme genes in roots remained mostly unchanged or were inhibited by the waterlogging, Fm up-regulated the expression of PpSOD3 and PpSOD7, whereas Si up-regulated the expression of PpSOD3, PpCAT1, PpGPX6, PpGPX8, and PpPOD1. In conclusion, low oxidative bursts in Fm- and Si-inoculated peach plants exposed to waterlogging were associated with an increase in total flavonoids as well as activities and gene expression of antioxidant enzymes.Graphical

Transcriptome Analysis Reveals the Molecular Mechanism and Responsive Genes of Waterlogging Stress in Actinidia deliciosa Planch Kiwifruit Plants

Waterlogging stress is one of the major natural issues resulting in stunted growth and loss of agricultural productivity. Cultivated kiwifruits are popular for their rich vitamin C content and unique flavor among consumers, while commonly sensitive to waterlogging stress. The wild kiwifruit plants are usually obliged to survive in harsh environments. Here, we carried out a transcriptome analysis by high-throughput RNA sequencing using the root tissues of Actinidia deliciosa (a wild resource with stress-tolerant phenotype) after waterlogging for 0 d, 3 d, and 7 d. Based on the RNA sequencing data, a high number of differentially expressed genes (DEGs) were identified in roots under waterlogging treatment, which were significantly enriched into four biological processes, including stress response, metabolic processes, molecular transport, and mitotic organization, by gene ontology (GO) simplify enrichment analysis. Among these DEGs, the hypoxia-related genes AdADH1 and AdADH2 were correlated well with the contents of acetaldehyde and ethanol, and three transcription factors Acc26216, Acc08443, and Acc16908 were highly correlated with both AdADH1/2 genes and contents of acetaldehyde and ethanol. In addition, we found that there might be an evident difference among the promoter sequences of ADH genes from A. deliciosa and A. chinensis. Taken together, our results provide additional information on the waterlogging response in wild kiwifruit plants.

Leaf ontogeny modulates epinasty through shifts in hormone dynamics during waterlogging in tomato.

Waterlogging leads to hypoxic conditions in the root zone that subsequently cause systemic adaptive responses in the shoot, including leaf epinasty. Waterlogging-induced epinasty in tomato has long been ascribed to the coordinated action of ethylene and auxins. However, other hormonal signals have largely been neglected, despite evidence of their importance in leaf posture control. To cover a large group of growth regulators, we performed a tissue-specific and time-dependent hormonomics analysis. This revealed that multiple hormones are differentially affected throughout a 48 h waterlogging treatment, and that leaf age determines hormone homeostasis and modulates their changes during waterlogging. In addition, we distinguished early hormonal signals that contribute to fast responses to oxygen deprivation from those that potentially sustain the waterlogging response. We found that abscisic acid (ABA) levels peak in petioles within the first 12 h of the treatment, while its precursors only increase much later, suggesting that ABA transport is altered. At the same time, cytokinins (CKs) and their derivatives drastically decline during waterlogging in leaves of all ages. This drop in CKs possibly releases the inhibition of ethylene- and auxin-mediated cell elongation to establish epinastic bending. Auxins themselves rise substantially in the petiole of mature leaves, but mostly after 48 h of root hypoxia. Based on our hormone profiling, we propose that ethylene and ABA might act synergistically as an early signal to induce epinasty, while the balance of indole-3-acetic acid and CKs in the petiole ultimately regulates differential growth.

Transcriptome analysis reveals ZmERF055 contributes to waterlogging tolerance in sweetcorn

Waterlogging is a major disaster damaging crop production. However, most sweetcorn cultivars are not tolerant to waterlogging, which severely threatens their production. In order to understand the genetic mechanisms underlying waterlogging tolerance in sweetcorn, this study conducted a comprehensive investigation of sweetcorn waterlogging tolerance at the levels of physiology, biochemistry, and transcriptome in two sweetcorn CSSLs (chromosome segment substitution lines), D120 and D81. We found that D120 showed increased plant height, root length, root area, adventitious root numbers, antioxidant enzyme activities, and aerenchyma area ratio compared to D81. The transcriptome results showed that 2492 and 2351 differentially expressed genes (DEGs) were obtained at 4 h and 8 h of waterlogging treatment, respectively. Genes involved in reactive oxygen species (ROS) homeostasis, photosynthesis, and alcohol fermentation are sensitive in the waterlogging tolerant genotype D120, resulting in enhanced ROS scavenging ability, adventitious roots, and aerenchyma formation. Additionally, ethylene-, auxin-, and ABA-related genes exhibited different responses to waterlogging stress in sweetcorn. We integrated transcriptome and differential chromosomal fragments data and identified that ZmERF055 on chromosome 9 was directly involved in waterlogging stress. ZmERF055-overexpressing plants consistently exhibited significantly increased waterlogging tolerance and ROS homeostasis in Arabidopsis. These results offer a network of plant hormone signaling, ROS homeostasis, and energy metabolism co-modulating waterlogging tolerance in sweetcorn. Additionally, the findings support ZmERF055 as a potential ideal target gene in crop breeding to improve plant waterlogging tolerance.

Growth Responses and Adventitious Root Formation of Cucumber Hybrid Lines in a Waterlogged Condition

Cucumber (Cucumis sativus L.) F1 hybrids are grown commercially in open-field or greenhouse conditions. Hybrids are well adapted to these settings due to directed breeding. In protected cultivation systems, a small rhizosphere volume and intensive, continuous fertigation predispose the roots to waterlogging (WL) conditions and potentially to hypoxia. However, high productivity is expected and achieved under these conditions. The aim of this study was to identify traits that play a role in this surprising behavior. Initial observations revealed the presence of a significantly higher number of adventitious roots (ARs) in three greenhouse (7–14) vs. three open-field cultivars (less than two) grown under normal conditions. Further on, two contrasting representative hybrids typically grown in open-field and in greenhouse conditions were subjected to WL stress. Declining oxygen levels in the media and increased alcohol dehydrogenase activity (ADH) in the roots were experienced during the WL treatment in both hybrids, with anaerobic metabolism triggered less intensively (~4-fold less ADH activity) in the greenhouse-type ‘Oitol’. The induction characteristics of cysteine oxidase (CysOx) genes, key components of the hypoxia sensing pathway, were used to confirm the hypoxic stress experienced by the roots. The lower extent of upregulation in CysOx genes expression agreed with the milder level of hypoxic stress in the roots of ‘Oitol’ than in ‘Joker’. The more efficient induction of AR formation with a ~50% increase upon waterlogging stress was found to be a prominent trait in ‘Oitol’, apparently helping root internal aeration and mitigating hypoxia. The shoot growth of neither hybrid was set back by hypoxic root conditions. ‘Joker’ plants maintained the same growth rate as that of the control, while the growth of ‘Oitol’ accelerated when its root system was flooded with nutrient solution. Acclimation processes to hypoxia were proposed to explain the lack of growth retardation in both varieties. This corresponded well with a general abundance of AR development in greenhouse-type (slicing) cucumbers that are typically cultivated in soilless systems.