Genetic diversity of Fusarium oxysporum f.sp. cepae the causal agent of onion root and basal rot disease

Root and basal rot caused by Fusarium oxysporum f.sp. cepae is one of the most important diseases of onions that causes significant economic losses in onions fields. To recognize the genetic diversity and relationship among isolates of the pathogen, 30 isolates which had been collected from Isfahan, Kerman, Ardebil and Fars provinces, Iran were studies in 2012. Pathogenicity diversity of the isolates was investigated by inoculation of all isolates on three cultivars of onion named Sefid Kashan, Sefid Ahvaz and Ghermez Azarshahr in greenhouse. Genetic diversity of the isolates was also investigated by RAPD and PCR-RFLP techniques using ITS1 / ITS4 primers. Molecular data were analyzed by NTSYS-pc software and isolates were then classified using Jaccard coefficient and UPGMA simulated methods. In pathogenicity experiment, onion bulbs infected with isolates were planted in pots and maintained in greenhouse with 25 ˚C, 70% RH and 12h light. The experiment was carried out in completely randomized design with five replications and disease severity for each isolate were assessed three weeks after planting. The results showed that disease severity of isolates was significantly different at 1% level of probability in different onion cultivars but no significant relationship was detected in pathogenicity variation and genetic diversity among the isolates.