Genetic Diversityof amony Fusarium oxysporum f. sp. melonis Isolates, The Causal Agent of Cantaloupe And Muskmelon Wilt in Iran

Fusarium wilt caused by Fuarium oxysporum f.sp. melonis is one of the most important disease of melon in Iran and some countries around the world. The purpose of this study was to investigatethe genetic diversity of this pathogen in Iran. In this study, 50 isolates of F. oxysporum were collected from melon plants(cantaloupe and muskmelon) with wilt and yellowing symptomsacross Iran. The isolates were identified using morphological criteria and their pathogenicity was confirmed. Genetic diversity of the isolates was then determined by rep-PCR technique using ERIC and BOX primers and NTSYS software. The results of pathogenicity testshowed that there were significant differences at the 1% level probability among the isolates in disease incidence, disease severity and plant growth parameres (fresh weight of roots and shoots). The highest disease incidence was observed in plants inoculated with isolates Race1-2,605, 606and 609and the highest disease severity was induced by isolates 607, H2, F-186-4 and F-186-6. Isolates F-186-1, F-66-4, F-186-4and H9had the highest and isolates F-186-6, F-66-4 and 501 had lowest effects on decrease of fresh weight of roots and shoots, respectively. Genetic diversity test divided the isolates into 4 groups A, B, C and D in 63% similarity level. This study showed that the genetic diversity among the isolates of F. oxysporum f. sp. melonis is high in Iran. There was no correlation among Rep groups, pathogenicity and geographic distribution of the isolates.