Effects Of Waterlogging Priming And Exogenous Ethephon Before Anthesis On The Tolerance Of Wheat To Post-Anthesis Waterlogging Stress And Its Physiological Mechanisms

Waterlogging is one of the major abiotic stress that affect wheat production, filling stage is the sensitive period of wheat due to waterlogging which leads to serious yield reduction. Therefore, exploring the methods to raise wheat resistance to waterlogging stress and its physiological mechanism is important for coping with abiotic stresses and reducing yield loss due to abiotic stresses in wheat production. In this study, wheat plants (Yangmai16) were subjected to two times of2-day waterlogging pretreatments, exogenous ethephon treatment on leaf and exogenous ethephon treatment in soil at two pre-anthesis stages (seven-leaf stage and nine-leaf stage), and then followed a7-day post-anthesis waterlogging stress from7days after post-anthesis in a pot experiment. The effects of waterlogging priming and exogenous ethephon treatment on photosynthesis, Membrane lipid peroxidation of flag leaf, leaf proteomics and grain yield under waterlogging stress were investigated in order to elucidate its physiological mechanisms for providing theoretical basis in wheat production. The main results were as follows:1. Waterlogging priming and exogenous ethephon before anthesis significantly increased photosynthetic ability of wheat flag leaf due to post-anthesis waterlogging stress. Waterlogging priming decreased photosynthesis rate of flag leaf to some extent, but compared with non-priming treatment, pre-anthesis waterlogging priming showed higher chlorophyll content, higher stomatal conductance, thereby maintain higher net photosynthetic rate in wheat leaf. Pre-anthesis exogenous ethephon can maintain higher chlorophyll content, photosynthesis rate and higher grain yield under post-anthesis waterlogging stress.2. Waterlogging priming and exogenous ethephon before anthesis can alleviate the damage of membrane lipid peroxidation caused by post-anthesis waterlogging stress. Compared with non-priming treatment, waterlogging priming and exogenous ethephon before anthesis can maintain lower MDA content and its damage to cells, increase soluble sugar content in flag leaf and osmotic adjustment ability, provide carbon and energy for organic synthesis. Exogenous ethephon treatment before anthesis can maintain higher relative water content to increase its tolerance to waterlogging.3. Waterlogging priming and exogenous ethephon before anthesis significantly affected the proteomic expression of wheat leaf. The results showed that pre-anthesis priming up-regulated the expression of protein related to ascorbate peroxidase, S-adenosyl methionine synthetase, Isocitrate dehydrogenase so as to increase the ability of eliminating active oxygen, ethylene production and energy supply, thereby improve the resistance to waterlogging. Compared with non-priming treatment, exogenous ethephon before anthesis can improve the expression of protein related to isocitrate dehydrogenase, malate dehydrogenase and ATP synthase, thus speeding up the decomposition of substance under post-anthesis waterlogging stress for stronger resistance of wheat to soil waterlogging.4. Waterlogging priming and exogenous ethephon before anthesis have different effects on wheat grain yield due to post-anthesis waterlogging stress. Compared with non-priming plants, waterlogging priming significantly increased1000-kernel weight, kernels and grain yield under post-anthesis waterlogging stress. Exogenous ethephon on leaf before anthesis can improve1000-kernel weight and grain yield, however, exogenous ethephon in soil reduced the grain yield of wheat. So exogenous ethephon on leaf had better effect on maintain grain yield in waterlogging stress.In summary, the waterlogging priming and exogenous ethephon before anthesis can significantly improve the photosynthetic ability, capacity of eliminating active oxygen and regulate expression of protein in leaf to affect resistance to waterlogging stress. Compared with non-priming treatments, waterlogging priming increased expression of protein related to ascorbate peroxidase, S-adenosyl methionine synthase, isocitrate dehydrogenase and other key enzymes. Exogenous ethephon can also influence the expression of protein in wheat leaves under post-anthesis waterlogging condition, increasing the expression of isocitrate dehydrogenase, malate dehydrogenase, phosphoglucomutase and ATP synthase, thereby regulating carbohydrate and energy metabolism to improve the resistance of wheat to waterlogging stress. Concerning about grain yield, waterlogging priming and exogenous ethephon on leaf can effectively alleviate damage to wheat production caused by post-anthesis waterlogging stress, and they can be used as methods to increase tolerance to waterlogging in wheat production.