Anastomosis groups of Rhizoctonia solani from cotton in northern China
中国北方棉花主产区立枯丝核菌的融合群鉴定

A total of 198 Rhizoctonia solani isolates were obtained from diseased cotton and soil samples in northern China(Shandong,Hebei and Henan provinces).Anastomosis group(AG) assay and 5.8S rDNA-internal transcribed spacer(ITS) sequence analysis showed the presence of multinucleate Rhizoctonia AG4-HG-I,AG4-HG-III and binucleate Rhizoctonia AG-A,AG-F and AG-Fb groups.The group AG4-HG-I was the dominant(86.86% of total isolates),followed by AG4-HG-III(10.10%),while the AG-A,AG-F,AG-Fb groups were represented by single isolate respectively.The Rhizoctonia AG-A,AG-F,AG-Fb groups were firstly reported from diseased cotton plants,and their pathogenicity to cotton needs further investigation.The 5.8S rDNA-ITS sequence analysis showed that the isolates could be distinctly separated based on their AG types.The isolates of the same AG(or sub-AG) showed high sequence identity.The nuclear phase observation showed that the numbers of nuclei were significantly different between the two subgroups of AG-4.