Grouping and rDNA-ITS sequence analysis of Thielaviopsis basicola on tobacco in China
中国烟草根黑腐病菌根串珠霉菌群及rDNA-ITS序列分析

Tobacco black root rot caused by Thielaviopsis basicola was frequently reported in China in recent years.In this study,a total of 45 isolates of wild types and 11 isolates of white aberrant phenotypes of the pathogen were collected from some provinces of China.According to Punja & Sun’s grouping standards,their grouping identification was conducted.The results showed that six general morphological groups could be distinguished among the isolates,in which groupsⅠ,Ⅱ and Ⅲ were wild types,groups Ⅳ andⅤ aberrant phenotypes.The characteristics of colony and chlamydospores of another aberrant phenotype HLL-1 was completely different from those of the five groups mentioned above,therefore it was assigned to the new group,group Ⅵ.The isolating ratios of groups Ⅰ,Ⅱ,Ⅲ,Ⅳ,Ⅴ and Ⅵ were 42.9%,33.9%,3.6%,16.0%,1.8% and 1.8% respectively.Group Ⅰwas mainly distributed in Chongqing and Yunnan,group Ⅲ and Ⅴ in Guizhou,group Ⅳ mainly in Chongqing,Henan and Yunnan,group Ⅵ only in Henan,and group Ⅱ was distributed in all investigating provinces.The rDNA-ITS sequence analysis suggested that the white aberrant phenotypes were identical to their wild types in sequences,but completely different from the isolates growing on other host plants.