Morphological and molecular characterization of sclerotium rolfsii associated with fruit rot of Cucurbita maxima

In the present study, fruit rot disease of Cucurbita maxima observed in many crop fields of Southern Karnataka, India is reported. The fruit rot disease on Pumpkin appears as water soaked lesion on the surface of the fruit followed by the development of large rotten areas with abundant white mycelial growth. The fungal pathogen was isolated on potato dextrose agar (PDA) medium and development of whitish fast-growing mycelia with numerous reddish brown sclerotia was observed. The sclerotia were initially white and turned dark brown upon maturation. Genomic DNA was isolated and internal transcribed region of ribosomal DNA was amplified using ITS1-ITS4 universal primers. Based on cultural, morphological and molecular characteristics, the fungal pathogen was identified as Sclerotium rolfsii. The rDNA sequence results also showed 99–100 % similarity with reference sequence AB075298.1 and JF966208.1 confirming pathogen identity. The pathogenicity test conducted on healthy detached fruits produced fruit rot symptoms after 6–8 days of post inoculation. S. rolfsii is known to infect many economically important crop plants at various stages of its growth and development. To the best of our knowledge, this is the first report on the association of S. rolfsii with fruit rot of C. maxima in India.