Field-grown cotton shows genotypic variation in agronomic and physiological responses to waterlogging

Context: Waterlogging frequently occurs and causes serious damage to cotton. While genotypic variation in waterlogging tolerance has been reported in cotton, there is limited research on the difference in waterlogging tolerance among Chinese commercial cotton varieties, and whether waterlogging tolerance is related to their geographical origin remains unclear. Methods: To this end, we conducted a comparative study to evaluate the waterlogging tolerance of commercial cotton varieties from three major cotton-growing regions in China. Field-grown cotton was subjected to seven days of waterlogging stress at early flowering. The effects of waterlogging on growth, seedcotton yield, yield reduction, and various physiological responses were assessed. Results: The losses of seedcotton yield and biological yield of cotton varieties from the Yangtze River valley were the lowest (7.6% and 4.7%), followed by those from the Yellow River valley (14.4% and 7.7%), while the losses of cotton varieties from the Northwest Inland were the greatest (21.8% and 15.5%). This indicated that cotton ecotypes from the Yangtze River valley and Yellow River valley, characterized by higher precipitation, exhibit greater tolerance to waterlogging than those from the Northwest Inland. The increases in H2O2, malondialdehyde (MDA), and abscisic acid (ABA) contents in the cotton variety from the Yangtze River valley (YZ1) were the lowest (10.8%, 18.6%, and 20.8%, respectively), followed by those from the Yellow River valley (YL1) (32.6%, 33.2%, and 79.9%, respectively), while the increases in cotton varieties from the Northwest Inland (NW1) were the greatest (37.9%, 42.8%, and 84.4%, respectively). The decreases in indole-3-acetic acid (IAA), nitric oxide (NO), and nitrogen (N) contents of YZ1 were the lowest (10.3%, 32.5%, and 25.6%, respectively), followed by those from YL1 (12.7%, 39.8%, and 30.2%, respectively), while the decreases of NW1 were the greatest (24.9%, 48.3%, and 45.1%, respectively). Quantitative real-time PCR analysis showed the highest expression of the NO (GhNIR) and IAA (GhYUC8) synthesis genes, but the lowest expression of the genes involved in H2O2 production (GhRBOHC), and ABA synthesis (GhNCED2) in YZ1, followed by those in YL1 and NW1, indicating that gene expression patterns aligned with the changes of NO, IAA, H2O2 and ABA contents. Ten days after waterlogging relief, waterlogged YZ1 exhibited the greatest increases in biomass, leaf area, and canopy photosynthesis (44.1%, 40.0%, and 46.4%, respectively), followed by YL1 (39.0%, 36.9% and 40.5%, respectively), while NW1 showed the lowest increases (36.3%, 32.6% and 35.4%, respectively), indicating stronger compensatory growth in the Yangtze River valley cotton variety. Conclusions: The results suggest that cotton varieties from the Yangtze River valley were more tolerant to waterlogging as evidenced by the lower level of damage and stronger compensatory growth than those from other geographical origins. We propose that quiescence adaptation and compensatory growth are the two main strategies employed by cotton to cope with waterlogging stress. This study enhances our understanding of the damage caused by waterlogging and sheds light on the adaptive mechanisms of cotton. Furthermore, it provides valuable insights for the breeding waterlogging-tolerant cotton varieties and improving cultivation practices.