Induction of Sexual Stage and Colony Morphology of Some Isolates of Sclerotium rolfsii Causing Spotted Leaf Rot in Plants

摘要

Twenty-two isolates of Sclerotium rolfsii causing spotted leaf rot from Varanasi, India were grown on 6% Cyperus rotundus rhizome meal agar (CRMA) medium for the induction of athelial stage (Athelia rolfsii). Only one isolate obtained from Sphaeranthus indicus formed basidial stage on CRMA medium while the other 21 isolates did not. Basidial stage was also produced in S. indicus isolate at different concentrations (5.5, 6.0 and 6.5% w/v) of CRMA medium. Size of basidia, steri-gmata and basidiosporesof this isolate was measured. Basidia clavate, hyaline and measured 10-12 x 4-5 μm in size, basid-iospores hyaline, unicellular, subglobose to ellipsoid produced on sterigmata and measured 3-5 x 2-4 μm in size, sterigmata hyaline and measured 4-5 x 1.5-2 μm in size. The results of the present study revealed wide variation in spotted leaf rot isolates of S. rolfsii. A reddish zone around the colony of S. rolfsii isolate from Vernonia sp. was observed on CRMA medium. HPLC analysis of the zone revealedthe presence of gallic and ferulic acid which were also thought to be responsible for reduced mycelial growth of the isolate on CRMA medium.