棉花黄萎病不同致病群菌系在河北省的分布

用中棉品种石系亚，海岛棉品系海７１２４和陆地棉品种９３抗１２，辽棉５号，冀棉１１号，农大３６５等６个鉴别寄主所得的病情比较，采用最长距离法对采集于河北棉区３７个重点植棉县的４０个黄萎病菌系进行了系统聚类，结果表明，４０个黄萎病菌素可划分为ＶＧＩ，ＶＧⅡ和ＶＧⅢ３个致病群（ＶＧｓ）分别包括２２，１２和６个菌系，基保ＶＧＩ的菌系致病力最强，鉴别寄主中除中棉品种石系亚表现抗（耐）病外，海岛棉品种海７１２

Distribution of the Isolates of Different Virulence Groups of Verticillium dahliae in Hebei Cotton-growing Areas

According to cluster analysis based on the disease indices in 6 differential cotton varieties, i. e. Shixiya (G. arboreum ), Hai7124(G. barbadense), 93K12, Liaomian 5, Jimian11and ND365(G. hirsutum), 40 strains isolated from the cotton fields of 37 key cotton-growing counties were classified into 3 virulence groups (VGs) . There exist 22, 12 and 6 isolated in VGI, VGII and VGIII, respectively. Isolates belonging to VGI possess high virulence, which make the Sea Island and Upland differential varieties susceptible, but Asiatic cotton resistant ortolerant. Strains of VG II are intermediately virulen, whereas those of VGIII are character ized by weak virulence. VG I strains principally distribute over the central-southem and southeastern parts of the province while VG II isolates predominate over the midddle and nort HebeiStrains of VGIII mainly exist in the cotton-growing areas along the Bohai sea coast and nearer Taihang mountain in northern Hebei province.