Eight isolates of Fusarium oxysporum f.sp. v8sinfeclum (FOV) were tested for
levels of pathogenicity on 45-c!aY- 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 (SDSĀ·
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.