PHENOTYPIC DIVERSITY AMONG ISOLATES OF Macrophomina phaseolina AND ITS RELATION TO PATHOGENICITY

Sixty isolates of Macrophomina phaseolina, the cause of charcoal rot, were isolated from different parts of Iran on various plants including cantaloupe, long melon, soybean, cucumber, apricot, rosemary and sesame. Phenotypic characteristics of the isolates were compared by growing on PDA at 35˚C. Colony appearance, growth rate, production and amount of sclerotia and also the relationship between growth rate at 35˚C and size of sclerotia were determined. In a greenhouse study, sclerotia of different phenotypes were mixed with the soil and soybean and cantaloupe plants were used for pathogenicity tests. After eight weeks root colonization was assessed. All treatments were arranged in a randomized complete block design with three replications. The data were analyzed using SPSS software. Isolates were grouped in four phenotypes: fluffy with abundant sclerotia, fluffy with few sclerotia, partially fluffy, and appressed growth. There was a significant difference between fluffy with few sclerotia and other phenotypes. Fluffy isolates with few sclerotia could not colonize soybean and cantaloupe roots. No significant differences were observed among other phenotypes on colonizing cantaloupe and soybean roots.