Screening And Identification Of Drought-resistant Wheat Germplasm At Seedling Stage

Due to changes in climatic conditions such as global warming,the frequency and scope of drought in China are increasing.Drought seriously limits the normal growth and development of wheat.Therefore,breeding wheat varieties with strong drought resistance is one of the important ways to cope with drought.In this study,100 wheat varieties(lines)were used as experimental materials,20 % PEG-6000 was used to simulate drought stress treatment,19 phenotypic indexes were measured,and drought resistance was evaluated and analyzed by principal component analysis,membership function and cluster analysis.Seven wheat varieties(lines)with high drought resistance,seven wheat varieties(lines)with moderate drought resistance and seven wheat varieties(lines)with drought sensitivity were selected according to the results of bud stage test.Two weeks after wheat emergence,two treatments of control and drought stress were set up by nutrient pot culture method.The catalase(CAT),peroxidase(POD),superoxide dismutase(SOD)and malondialdehyde(MDA)of different varieties(lines)of wheat seedlings were measured,and the changes of physiological indexes under drought stress were analyzed.Two molecular markers(1-feh-w3 and Dreb-B1)related to drought resistance were used to detect KASP markers in 100 wheat varieties(line s).The main results are as follows :1.The correlation analysis of 19 phenotypic traits and drought resistance coefficient under distilled water and drought stress conditions showed that there was no significant correlation between stem diameter(SD),coleoptile length(COL),root surface area(RA),root volume,fresh root shoot ratio and dry root shoot ratio under drought stress,and there was significant correlation between the other indexes.Through principal component analysis,each index was re-summarized into four relatively independent new comprehensive indexes,and the cumulative contribution rate reached 80.321 %.That is,germination traits,root biomass traits,biological yield,and root-shoot ratio can be used as comprehensive evaluation indexes for identifying drought resistance of wheat at germination stage.2.The D value was calculated by using the weight and membership function value to evaluate the drought resistance of 100 wheat varieties,and then the D value was used to classify the wheat varieties according to the cluster analysis map obtained by the system clustering method.According to the cluster analysis diagram,100 wheat varieties(lines)were divided into five categories : high drought resistance type,drought resistance type,moderate drought resistance type,drought sensitive type and drought highly sensitive type.There were 7 varieties(lines)in the first category,12 varieties(lines)in the second category,70 varieties(lines)in the third category,8 varieties(lines)in the fourth category and 3 varieties(lines)in the fifth category.3.The analysis of physiological and biochemical indexes of different drought-resistant wheat varieties(li nes)at seedling stage showed that CAT,SOD activity and MDA content under drought stress were higher than those under normal watering,and POD activity was lower than that under normal watering.Among the three different drought-resistant varieties,the CAT and SOD activities of highly drought-resistant varieties were stronger than those of moderately drought-resistant and drought-sensitive varieties.The POD activity and MDA content of highly drought-resistant varieties were lower than those of moderately drought-resistant and drought-sensitive varieties.4.KASP marker detection was carried out on 100 wheat varieties(lines).Two alleles of Kauz type and Westonia type were detected in 1-feh-w3,and two alleles of Dreb-B1 + and Dreb-B1-2 were detected in Dreb-B1.The phenotypic data between different sites were used to analyze the differences by box plot.It was found that the germination potential and germination index were higher at the sites such as Kauz type of 1-feh-w3 gene,and the plant height,fresh weight,dry weight,root length,root surface area and root volume were higher at the sites such as Westonia type of 1-feh-w3 gene.The germination rate,stem diameter,coleoptile,total dry weight and root number of Dreb-B1-were higher,and the vigor index,underground fresh weight,underground dry weight and total fresh weight of Dreb-B1 + were higher.In summary,drought-resistant varieties were screened out through phenotypic traits,combined with the changes of protective enzymes and MDA content under drought stress,and finally 16 varieties were screened out according to KASP molecular marker detection and effect analysis.They were Huacheng 863,Shanken 81,Ningchun 45,Luohan 7,Longjian 115,Yangao 21,Xiaoyan 22-3,Xumai 1108,Luomai 8,Cunmai 12,Ligao 6,Gushen 1,Huaihe 12013,Lunxuan 715,SD29589,Clearwhite.