[Genetic diversity and phylogenetic analysis of Fusarium oxysporium strains isolated from the Cucurbitaceae hosts revealed by SRAPs].

Cucurbitaceae wilt of different hosts could be caused by Fusarium oxysporum. To clear the genetic diversity and phylogenetic relationship of F. oxysporum isolates from different Cucurbitaceae hosts and regions, genomic DNA of ninety-five strains of F. oxysporum isolated from different hosts and different regions were amplified by sequence-related amplified polymorphism (SRAP) molecular markers. All strains could be uniquely distinguished with 238 polymorphism bands which generated 100% of polymorphic ratio with 19 selective primer pairs. On average, each primer pairs amplified 12.5 loci and 12.5 polymorphic loci. A total of 166 bands of F. oxysporum f. sp. momordicae (FOM) were amplified, among which 145 polymorphic bands generated 87.4% of polymorphic ratio. On average, each primer combination amplified 8.7 loci and 7.7 polymorphic loci. This indicated that genetic variation of F. oxysporum was extensive. The genetic similarity coefficient of F. oxysporum was 0.68-0.99, and the average indexes of Nei's genetic diversity and Shannon were 0.2390 and 0.3718, respectively. Ninety-five strains of F. oxysporum were divided into four formae speciales from bitter gourd, cucumber, watermelon and melon, when the genetic similarity coefficient was 0.74. In SRAP dendrogram all the FOM isolates were gathered into one phylogenetic branch with the genetic similarity coefficient ranging from 0.78 to 0.99. The average indexes of Nei's genetic diversity and Shannon indices were 0.1811 and 0.2750, respectively. This indicated that genetic diversity of FOM was abundant, and the classification of phylogenetic group was related to geographic origin to some extent.