Effects Of High Temperature And Drought Stress After Anthesis On Starch Synthesis In Wheat

In this experiment,Zhengmai 366 and Yumai 49-198 were used as experimental materials to study the effects of different day and night temperature and soil moisture model on the transport of wheat material,starch synthesis and yield of wheat in the field of pot and grain filling stage.The results show that:1.During grain filling stage,high temperature,drought stress and their combined stress caused the decrease of photosynthetic pigment content of wheat,reduced the dry matter transport and translocation rate before flowering and its contribution to grain,but increased the contribution rate of assimilate to grain after anthesis.Compared with different treatments,the effect of high temperature on photosynthetic pigments and matter transport of grains was greater than that of drought,and the effect of compound stress was greater than that of single factor stress.Zhengmai 366 was more significantly affected by stress.2.Compared with the control,the high temperature,drought and compound stress shortened the growth period of wheat and reduced the grain weight and yield.Compared with different stress treatments,the effect of high temperature stress treatment was greater than drought stress,and the composite stress treatment was greater than single factor stress,showing a significant additive effect.Comparing the two varieties,Zhengmai 366 is more susceptible to temperature and water stress than Yumai 49-198.3.During the grain filling stage,high temperature,drought,and combined stress accelerated the grain filling process of wheat,reduced the rate of starch accumulation,resulting in a decrease in the content of amylose,amylopectin,and total starch,and a higher ratio of straight/branch,and adverse stress on amylopectin is greater than that of amylose.Comparing various stress treatments,the effect of high temperature stress on starch accumulation in wheat was greater than that of drought,and the compound stress was greater than single factor,and the two varieties showed consistent performance.The grain starch accumulation of Zhengmai 366 was more susceptible to adversity stress than that of Yumai 49-198.4.Compared with the control,the high temperature,drought and compound stress during grain filling all led to the advance of the activity of the key enzymes(AGPase,SSS,GBSS,SBE,SS)in wheat grain starch,and the peak activity decreased(SS of Zheng Mai 366 except for DS processing).Comparing the treatments,the effect of high temperature on the activity of key enzymes in grain starch synthesis was greater than that of drought,and the compound stress exhibited a significant additive effect.Comparing the two varieties,high temperature and drought had a greater effect on the activities of key enzymes in starch synthesis in Zhengmai 366.5.The Zhengmai 366 was used as the experimental material to study the expression of enzymes involved in starch synthesis.Compared with the control,the high temperature during grain filling stage reduced the relative expression of starch synthesis-related enzyme genes,and drought stress increased the expression levels of AGPL1,AGPS1-a,AGPS1-b,SSI,SSIIa,SSIIc,SSIIIa,BEI,BEIIb,ISA2,and PHOH genes,which ultimately reduced the relative expression levels of AGPS2,AGPL2,GBSSI,GBSSII,SSIIb,SSIIIb,SSIV,BEIIa,BEIII,ISAI,PUL,and PHOL.Correlation analysis revealed that there was a significant positive correlation between a series of AGPase isoenzyme genes and their corresponding enzyme activities at the late filling stage(AGPS2 was positively correlated with AGPase activity throughout the assay period).And the GBSS isoenzyme gene(GBSSI,GBSSII)were extremely significant positive with its corresponding enzyme activity at 22 d and 26 d after anthesis,respectively.There was an extremely significant positive correlation between the SSS isoenzyme gene and its corresponding enzyme activity at the late filling stage(22 d to 26 d after anthesis)(SSIIb was expressed at the early stage of grain filling).There was a significant positive correlation between a series of SBE isoenzyme genes(BEI and BEIIa)and their corresponding enzyme activities at the range of 18 d to 26 d after anthesis,and there was a significant positive correlation between BEIII and SBE activity.at the early filling stage(14 d after anthesis).The above results indicate that a series of starch synthase isoenzyme genes influence the activity of starch synthase through their respective roles in different periods,and thus affect starch accumulation.