Preliminary Study On Pathogenicity Of Verticillium Dahliae In Soil And Its Vegetative Compatibility

In order to explicit the pathogenicity of Verticillium dahliae in soil and to provide the theoretical testimony for the aberrance rule of pathogen,in August 2005, we have identified the Verticillium dahliae in the disease garden in the Doukou county, Shaanxi province. The cultural character of 26 representative strains of V. dahliae on the PDA substrate showed that there are three cultural type: black (sclerotium type), white (filamentous fungus) and middle. Furthermore, the growth quantity, formation of micro-sclerotium, fabric, color, size and relative amount of melanin of colony of those 26 representative strains of V. dahliae were different from observation.The biological characteristic studies with 14 representative strains shown that the option temperature of grows for V. dahliae is 25℃, and a few strains can quickly grows in 20℃, However all strains can not grow in 33℃.In addition, the determination of pathogenicity in the seedling stage has also showed that difference exist among the 26 representative strains. According to the reaction types on 5 species cottons with different resistance, all strains can be classed into three pathogenic types: type1 (12 isolates accounted for 41.6% of the total) was characterize by severe virulence, type2 (9 isolates, accounted for 34.6%) showed mild virulence and type3 (5 isolates, accounted for 19.2%), an intermediate type.After that , in order to explicit the relationship about pathogenicity and vegetative compatibility(VGC) of Verticillium dahliae in soil, we have studyed vegetative compatibility of those 26 strains of Verticillium dahliae .Based on the formation of complementary heterokaryons, 295 Nitratenonutilizing (nit) mutants were obtained from 28 strains which induced on KPS media ,in which 235 mutants were Nit1,It accounted for 9.66% of the total;59 mutants were nitM, only one strain was Nit3.They also showed that 28 strains were assigned to two vegetative compatibility groups (VCGs): 26 representative strains of V. dahliae and jing-yang strain were compatible with each other and classified into the first VC group(VGC1),while xin-jiang strain was classified into the second VC group(VGC2).