USE OF PATHOGENICITY AND ELECTROPHORETIC PROTEIN PATTERNS TO DISTINGUISH ISOLATES OF Fusarium oxysporum f.sp. vasinfectum PATHOGENIC ON COTTON

Abstract

Eight isolates of Fusarium oxysporum f.sp. v8sinfeclum (FOV) were tested for levels of pathogenicity on 45-c!aY-<lfd greenhouse-grown seedlings of six cotton genotypes. Isolate x genotype interaction was a very highly significant (p = 0.0094) source of variation in wilt incidence suggesting that isolates responded differently to different genotypes. Due to the significance of isolate x genotype interaction. a least significant difference (LSD) was used to compare between the individual isolate means within genotypes. based on these comparisons. it was easy to differentiate between some of FOV isolates by their differential pathogenicity on some of the genotypes. On the other hand, some isolates was indistinguishable because they showed nonsignificant differences on any of the genotypes. Proteins of the isolates were compared by sodium dodecyl sulfate-polyacrylamide gel electrophoresiS (SDS· PAGE).. Gels were stained with Coomassie Brilliant Biue R-250 (CBB) or silver nitrate (SN). Cluster analysis of the protein banding patterns by the unwelghted pair-group method based on arithmetic means (UPGMA) placed the isolates in several group$. Similarity levels among the isolates on staining with SN were less than those of CBB, which indicates that SN was more sensitive than CBB to detect the differences among the isolates in protein banding patterns. There were isolates specific bands by which isolates, particularly those belonged to different groups, could be identified. Some isolates. which were Indistinguishable by pathogenicity test. were easily distinguished by their specific bands after staining with SN. The results of the present study indicate that isolates of FOV could be identified by their differential pathogenicity on a set of cotton genotypes, combined with their specific parotein bands separated by electrophoresis and stained with SN.