Pathogenicity Differentiation And Vegetative Compatibility Determination Of Verticillium Dahliae Of Cotton In Shaanxi

Verticillium dahliae which, affect severly in Shaanxi cotton area and displav various kind of symptoms, has become main abstruct in cotton production. So, to verify the condition that pathogenity of Shaanxi Verticillium dahliae varies., show the principle of pathogen genetic variation, provide theoretical evidence for making disease control measurements, this thesis abtained the following results through studying cultural characteristic, pathogenity test and vegetitive compatibility of Verticillium dahlias collected from Shaanxi main cotton area:*'1. 26 strains- of Verticillium dakliae collected from Shaanxi main cotton and. T-9 strain.VD-8strainjinyang strain and anyang- strain were tested the pathogenity. The-result indicated that the pathogenicity variation, of strong, intermediate, and weak existed among the 30. tested strains. Strong pathogenicity' type included 15 strains and accounted for 50.0% of the total strains tested. Intermediate pathogenicity type included 9 strains and accounted-for 30.0% of the total strains tested. Weak pathogenicity type included 6 strains and accounted for 20.0%of the-total strains tested. It clearly indicated that there was the differentiation in pathogenticity among strains of V.dahliae tested and strains with strong pathogenicity occupied the dominant position.2. According tothe pathogenicity result, 20 different pathogenicity types typical strains were chosen to test biological characteristics. The result showed that colonial morphology of strains tested had three main typee: microsclerotia type, filamentous type, intermediate- type. Among them, microsclerotia type strains with- the strong pathogenicity took the largest-proportion, filam entous type strains with the strong pathogenicity took the smallest proportion. intermediate type strains had- a weak pathogenicity. Therefore, results revealed that the cultural characteristics of strains of V.dahliae had a close relation to its pathogenicity. Besides, greater difference about mycelium and spore production existed in the different cultural condition, while, it was the best condition for mycelium and spore production that Verticillitim dahlias of cotton strains were cultured on 20jC with light.3 The vegetative compatibility test showed that 20 strains were assigned to three vegetative compatibilty groups (VCGs), T-9 strain and VD strain were classified as VC group two (VGC2), while anyang stain classified as VC group three- (VGC3), other 17 strainsclassified as VC group one (VGC3). Additionally, results revealed that there was a relationship between the pathogeni city and vegetative compatibility. Strains from VGCi which had strong pathogenidty were found that myclium grew faster and compatibility band were wider: Strains from VGC2 which had weak pathogeni city were found that myclium grew lower and compatibility band were narrower: Strains from VGC3 had intermediate pathogenicity. There was no defoliatingpathotypes strain among the.17 Verticilliwn dahlkte of cotton strains in Shaanxi cotton area'...