RESTRICTION-FRAGMENT-LENGTH-POLYMORPHISMS, RACES AND VEGETATIVE COMPATIBILITY GROUPS WITHIN A WORLDWIDE COLLECTION OF FUSARIUM-OXYSPORUM F SP GLADIOLI

Isolates of Fusarium oxysporum f.sp. gladioli were collected from wide ly different geographic areas. These isolates were characterized by pa thogenicity to two differential gladiolus cultivars, vegetative compat ibility, and total genomic DNA restriction fragment length polymorphis ms (RFLPs). RFLPs were used to estimate the genetic divergence and rel ationship among isolates of F. oxysporum. RFLPs were detected by South ern blot hybridization of total genomic DNA with a 3.4 kb DNA probe ge nerated from total DNA of F. oxysporum f.sp. dianthi. Cluster analysis allowed the division of pathogenic strains into three main RFLP group s, each group containing strains with similarity coefficients ranging from 78 to 100%. RFLP groups correlated with vegetative compatibility groups, not with races. Two single pathogenic isolates which could not be assigned to any of the three main vegetative compatibility groups also had distinctive RFLP patterns. Little genetic polymorphism was ob served within vegetative compatibility groups, whereas the majority of RFLPs occurred between vegetative compatibility groups, suggesting a common ancestry for strains within a specific vegetative compatibility group and a polyphyletic origin for the present special form gladioli .