Screened For Heat Tolerance Of Wheat Germplasm Resources In The Yellow And Huai River Valley Winter Wheat Zone And The Middle And Lower Yangtze Valley Winter Wheat Zone

Wheat is one of the important food crops in China,providing approximately 20%of daily calories and protein for human nutrition.Wheat is one of the most cultivated crops in temperate climates.However,with the global climate has been steadily warming over recent decades,wheat often suffers heat stress at some stage during its life cycle.Studies have shown that wheat production could decrease by 6%for each 1℃of further temperature increase.At present,only a few evaluation indices were used for the selection of heat tolerance wheat and the heat tolerance wheat germplasm resources are relatively scarce.Therefore,it is important to find the reliable screening methods and effective selection criteria to identify heat tolerant wheat varieties.In this work,a total of 169 winter wheat varieties(136 from Yellow and Huai River Valley Winter Wheat zone and 33 from Middle and Lower Yangtze Valley Winter Wheat Zone)were phenotyped for spike length,total spikelet number,fertile spikelet number,kernel number per spike,thousand kernel weight,kernel length and kernel width under normal-sown(NS)and late-sown(LS)conditions.High-throughput method based on the HSI of trait and comprehensive evaluation index were performed to evaluate heat tolerance of wheat germplasms.The results are as follows:1.169 spring wheat varieties were selected and sowed in two stages(normal and late stage)in two years.The spike length,kernel number per spike,thousand kernel weight,yield per plant,kernel length,kernel width,total spikelet number and fertile spikelet number were investigated and analyzed.Compared with the normally planted wheat,the late sown wheat suffered a higher temperature in each growth period,and the duration of each growth period was significantly shortened;spike length,kernel number per spike,thousand kernel weight,yield per plant,kernel width,total spikelet number and fertile spikelet number were decreased significantly.2.The correlation analysis on the agronomic traits in the two sowing dates showed that kernel length was significantly positive correlated with kernel width(r=0.83);fertile spikelet number was positively with total spikelet number(r=0.95);kernel number per spike(r=0.79);and thousand kernel weight was positively correlated with kernel length and kernel width3.High-throughput method based on the heat susceptible index of thousand kernel weight,kernel width,spike length,kernel number per spike,total spikelet number and fertile spikelet number were performed to evaluate heat tolerance of 169 wheat varieties.Overall,8significant heat tolerant varieties whose heat susceptibility index is less than 0.5 were screened out,such as Lumai 11,Zhengzhou 8960,Lianmai 2,Yannong 15,Wan 7107,Chiyacao and Nanda 96co76.4.Five independent comprehensive components were obtained from seven traits by using principal component analysis,and their contribution rates respectively were 42.21%,23.33%,11.64%,10.38%and 7.55%,which reflected 95.11%information of all traits information.The comprehensive heat tolerance values(D)were calculated from the membership function methods.The results showed that 169 wheat materials were divided into 4 categories ranging from highly heat tolerant to highly heat sensitive types,highly heat tolerance(D≥0.730),medium heat tolerance(0.5.74≤D<0.730),medium heat sensitive(0.360≤D<0.574),highly heat sensitive(D<0.360).Among them,Zhengzhou 8960,Zhongjiao 1,Wan 7107,AimengniuⅣ,Lumai 11,Wanyuan 66,Ningmai 15,Emai 17 and Yangmai 11 were identified as highly heat tolerance material.A mathematical evaluation model from heat tolerance of wheat was established using the stepwise regression equation:D=1.044-0.031×KNS-0.03×KW-0.334×YPP-0.04×FSN-0.032×TKW(R~2=0.974,P<0.001).The results showed that kernel number per spike,kernel width,yield per plant,fertile spikelet number,and thousand kernel weight could be used to identify wheat heat tolerance varieties.