304份橡胶树魏克汉种质冬春季叶片物候与白粉病病级多样性分析OA

This study aimed to screen elite germplasms with resistance or escape to powdery mildew,thereby providing theoretical basis and material support for disease-resistant breeding of Hevea brasiliensis.A total of 304 Wickham germplasm of H.brasiliensis were used as materials to systematically investigate the genetic diversity of botanical traits,leaf phenological and powdery mildew disease grades during late winter and spring,and cluster analysis was conducted.The results showed that the genetic diversity indices of 33 botanical traits ranged from 0.23 to 1.40,and the Shannon-Wiener diversity indices of 12 quantitative leaf morphological traits varied from 1.66 to 2.22.The genetic diversity index of leaf phenology in winter and spring ranged from 0.85 to 1.70,reaching the highest on February 9,and the lowest on April 3.The genetic diversity index of powdery mildew disease grade varied between 0.88 and 1.37,with the highest diversity observed on March 20,when 99％of the germplasm accessions were infected by powdery mildew.Correlation analysis between leaf phenology and powdery mildew disease grade indicated that the copper-red to discoloration transition stage and the discoloration stage of leaves on March 5 were the critical susceptible periods to powdery mildew.At this stage,leaf maturity showed a significantly strong negative correlation with powdery mildew disease grade(r=-0.48).It is recommended to regard this period as a crucial susceptible stage for the prevention and control of powdery mildew.Based on clustering analysis of leaf phenology and powdery mildew disease grade,the 304 germplasm were divided into six groups.Among them,Groups Ⅰ and Ⅱ exhibited similar high susceptibility,differing primarily in that Group Ⅰ displayed earlier leaf phenology.Similarly,Groups Ⅳ and Ⅴ showed moderate susceptibility,with Group Ⅴ distinguished by its earlier phenology.Notably,Group Ⅲ was characterized by early leaf abscission,while Group Ⅵ showed the latest leaf defoliation,both with relatively low disease grades.Combined with the growth dynamics of leaf phenology and powdery mildew disease grades,five germplasm accessions including No.21,No.152,No.166,No.222 and No.290 were screened out with the mildest disease susceptibility.This study clarified the phenotypic diversity of Wickham germplasm in H.brasiliensis and the correlation rules between phenology and powdery mildew occurrence,and identified superior disease-resistant and disease-escaping materials,which can provide important references for powdery mildew resistance breeding of H.brasiliensis.