Diversity of Macrophomina phaseolina isolates causing root rot of safflower

Isolates of Macrophomina phaseolina responsible for root rot of safflower were collected from Parbhani, Latur and Hingoli districts of Marathwada region of Maharashtra State, and assessed for phenotypic and pathogenic diversity. The isolates showed wide differences in colony characters, growth rate, sclerotia formation and virulence. Highest mycelial growth was recorded by isolate Mp8 (78.8 mm) while least by Mp9 (48.5 mm). Formation of pycnidia on PDA was recorded in Mp1 isolate. Based on percent seeding mortality, the isolates were categorized in four groups viz., highly virulent (Mp4, Mp9, Mp10); virulent (Mp3); moderately virulent (Mp6, Mp5, Mp2) and weakly virulent (Mp8, Mp7, Mp1). Isolates producing few small sclerotia were found less virulent, while thosewith abundant large sclerotia were highly virulent.