Comprehensive Evaluation of Drought Tolerance and Physiological Regulatory Mechanism of Wheat Seedlings

Liu Yuhang; Shi Yuhan; Yang Yiting; Li Xueting; Jiang Mengxin; Li Jiayi; Li Junhua; Sang Shifei; Feng Liuchun; Wang Li

doi:10.15933/j.cnki.1004-3268.2026.07.001

Abstract：With 120 wheat germplasms as materials,PEG6000 solution was used to simulate drought stress at seedling stage.Plant height,root length,fresh weight of shoot,dry weight of shoot,fresh weight of root,dry weight of root,root-shoot ratio and SPAD value were determined,and their drought tolerance coefficients were calculated.Principal component analysis(PCA)was performed based on their drought tolerance coefficients,cluster analysis was conducted using the comprehensive drought tolerance value(D),and comprehensive evaluation of drought tolerance of wheat germplasms was carried out.Highly drought-tolerant and drought-sensitive germplasms were selected to determine H2O2,malondialdehyde(MDA),proline(Pro),soluble sugar(SS)contents and catalase(CAT)activity,so as to analyze the physiological regulatory mechanism of drought tolerance.The pre-experiment confirmed that 25%was the optimal PEG6000 concentration,all phenotypic traits showed extremely significant difference compared with the control under this concentration.Drought stress obviously decreased fresh weight of shoot,dry weight of shoot,and SPAD value,but increased root length and root-shoot ratio.The correlations among phenotypic traits changed obviously under drought stress compared with those under normal water condition.Under drought stress,the correlation between root length and dry weight of shoot disappeared,SPAD value was significantly positively correlated with plant height and fresh weight.Genotype,drought and their interaction had extremely significant effects on all eight phenotypic traits.PCA showed that the first four principal components accounted for 86.67%of the total variation.The drought tolerance coefficients of all traits were extremely significantly positively correlated with D value,among which the correlation coefficients between drought tolerance coefficients of fresh weight of shoot,dry weight of shoot,fresh weight of root,dry weight of root and D value were higher,which were core indexes for drought tolerance identification.Cluster analysis based on D value showed that the wheat germplasms were divided into five groups,and 15 highly drought-tolerant germplasms were screened out,including Xinong 109,Luohan 22,Shannong 116,Xinmai 26,Yu'an X208,Bainong 207,Luyuan 502,Bainong 4199,Xinmai 60,Xinong 519,Wenmai 801,Saidemai 8,Yunong 186,Xinong 20,and Fengdecun 20.Compared with highly drought-sensitive germplasms,highly drought-tolerant germplasms had significantly lower H2O2 and MDA contents,and significantly higher CAT activity,Pro and SS contents,and CAT activity,Pro and SS contents were significantly or extremely significantly positively correlated with D value,indicating that highly drought-tolerant germplasms alleviate drought damage by enhancing CAT activity,accumulating Pro and SS,and reducing H₂O₂ and MDA accumulation.