Analysis Of The Effects Of Drought,High Temperature And Their Interaction On The Grain Development Of Wheat During Filling Stage

In recent years,a variety of adversities such as drought and high temperature have occurred frequently in winter wheat areas in China,and wheat yield and quality have been significantly affected.This study analyzes the response of wheat under drought,high temperature and their interaction stress,in order to provide a theoretical basis for drought resistance improvement and cultivation technology integration of high-quality wheat varieties.This experiment was carried out in 2017-2019 in the greenhouse of the South Campus of Northwest Agriculture and Forestry University of Science and Technology in Yangling,Shaanxi,and the Key Laboratory of Wheat Biology and Genetic Breeding in the Northwest Region of the Ministry of Agriculture and Rural Areas.As materials,the effects of drought,high temperature and their interaction stress at different filling stages on wheat growth,grain quality and gene expression of key enzymes were analyzed.The main conclusions are as follows:1.Effects on flag leaf physiology:(1)Under continuous drought stress,the relative water content of the flag leaf drops and photosynthesis is significantly inhibited;the soluble protein,soluble sugar and proline content of the flag leaf increases;The activities of enzymes(POD),catalase(CAT),superoxide dismutase(SOD)and ascorbate peroxidase(APX)increased.With the prolonged drought stress,the activities of CAT and APX continued to decrease compared with the control.The activities of POD and CAT first decreased and then increased.(2)High temperature stress in different periods of grain filling period reduced the net photosynthetic rate;high temperature stress in the early filling period promoted the accumulation of proline,inhibited the accumulation of soluble protein and soluble sugar,inhibited the accumulation of soluble globulin,soluble sugar and proline in the middle stage,and promoted the accumulation of soluble sugar in the later stage High temperature stress in the early and middle grain filling period increased APX and CAT activity,later CAT,SOD and APX activity increased,POD activity decreased.(3)Drought and high temperature interaction stress in different periods of grain filling period significantly reduced the relative water content of flag leaves,and photosynthesis was significantly inhibited;interaction stress in the early stage of grain filling inhibited the accumulation of soluble protein and soluble sugar,promoted the accumulation of proline,and promoted the soluble protein and preserved fruit Accumulation of lysine inhibits the accumulation of soluble sugar and promotes the accumulation of soluble sugar and proline in the later period;the interaction stress in the early and mid-grouting stage decreases the activity of POD,CAT and SOD,the interaction stress in the later period increases its activity,and the interaction in the early stage Under stress,APX activity increased.With the delay of treatment time,its activity decreased first and then increased.2.The effect on agronomic traits: drought,high temperature and their interaction stress caused the wheat filling period to be shortened significantly.Continuous drought stress and drought and high temperature interaction stress significantly reduced the 1000-grain weight of grains and reduced the length and width of mature grains;high-temperature stress at different stages during the filling period resulted in a reduction in the length and width of mature grains(except mid-filling period).The sooner the impact is greater.Continuous drought stress and drought and high temperature interaction stress significantly reduced plant height.3.Effect on grain starch:(1)Continuous drought stress reduces the content of grain starch and its components,and reduces the straight/branch ratio of mature grain.High temperature stress increased the content of amylose in grains,the content of amylose,amylopectin and total starch in mature grains decreased,and the ratio of amylose to branch increased.(2)Under drought stress,the accumulation amount of A-type starch granules in each stage was lower than that of the control,and A-type starch granules were less full and cracked than the control 20 days after flowering.In the early stage of grain filling,the accumulation rate of starch under high temperature and drought interaction was faster,but the number of A-type starch grains was still lower than that of the control at 30 days after flowering.4.Effects on grain protein:(1)Continuous drought stress and drought and high temperature interaction stress increase grain protein content,and high temperature stress decrease grain protein content.Studies on mature grain proteins and their components show that continuous drought stress increases total protein content,gliadin content decreases,gluten content increases,gluten / alcohol ratio increases significantly,and high temperature stress and interaction stress during early grain filling make alcohol soluble The content of protein,gluten and total protein increased.Under the interaction stress,the gluten / alcohol ratio increased significantly.The high temperature stress in the middle of grain filling increased the gliadin content,the gluten content decreased,the total protein content decreased,the gluten / alcohol ratio was significant Decreased,interaction stress increased the content of prolamin,gluten and total protein,high temperature stress in the later stage of grain filling reduced the content of prolamin,gluten and total protein,and interaction stress increased the content of prolamin and gluten.(2)Under continuous drought stress,the content of glutinin macropolymer(GMP)increased in the early and middle stages of grain filling,and decreased in the later stage of grain filling.With the delay of the occurrence of high temperature stress,the GMP content increased significantly.The GMP content increased during the middle filling stage.Drought,high temperature and interaction stress at different stages during the filling stage increased the GMP content of mature grains.5.RNA-Seq analysis found that the high temperature in the early stage of grain filling and its interaction with drought caused sucrose synthase,UDP-glucose pyrophosphorylase,bound starch synthase,soluble starch synthaseand starch branching enzymegenes were significantly up-regulated.High temperature in the late filling stage and drought stress changed some genes of starch branching enzymegenes from significantly up-regulating to down-regulating.And glutamate synthesis has a more significant effect,the key genes of glutamine synthetase and glutamate synthetase are significantly up-regulated.