Pathotype Identification and Host Resistance Evaluation of Clubroot in Zhejiang Province, China.

Clubroot, caused by , is a globally destructive soilborne disease affecting cruciferous plants. In this study, the predominant pathotypes of . in six cities within Zhejiang Province were identified using the Williams and European clubroot differential (ECD) systems. A phylogenetic analysis of . isolates infecting cruciferous crops worldwide was conducted using MEGA, and their ITS2 secondary structures were predicted through the ITS2 database. Accessions of , . , . , and Mill. were employed to assess clubroot resistance. The results revealed that the prevalent pathotypes in Zhejiang Province were pathotype 1, ECD20/31/12 and ECD24/16/30; pathotype 3, ECD20/15/4; pathotype 8, ECD16/0/0 and ECD24/0/0; and pathotype 2, ECD16/15/15. Isolates from distinct genera of Brassicaceae formed separate branches in the evolutionary tree. Moreover, isolates of crops from Zhejiang Province exhibited homology with those from other global regions, a finding corroborated by their ITS2 secondary structure. Approximately 80 and 95% of . and . crops displayed susceptible phenotypes for pathotype 8, ECD16/0/0, whereas approximately 60% of . crops exhibited resistance. Furthermore, three crop accessions showed significant variation in resistance to the pathogen, both among morphological and geographical origin groups. This study contributes to understanding the distribution of diverse . pathotypes in different regions of Zhejiang Province and facilitates the identification of crops with potential disease resistance suitable for cultivation in the province.