FIRST REPORT OF A LEAF SPOT DISEASE CAUSED BY SCLEROTIUM ROLFSII ON JASMINIUM MULTIFLORUM IN INDIA

Abstract

Jasminium multiflorum is an important crop grown ex- tensively in parts of Southern India. A characteristic leaf spot disease was observed during field surveys conducted in 2013-2015. The disease incidence ranged from 18 to 23% over about 45 cropped hectares. Water-soaked lesions (2-8 mm) appeared initially on the basal leaves followed by the development of large necrotic spots (0.5-1.5 cm) with sclero- tial bodies at the center of the necrotized areas. Affected leaf tissues were surface-sterilized with 2% NaOCl, transferred onto potato dextrose agar (PDA) and incubated at 28±2°C. Fungal colonies with dense, aerial whitish cottony mycelium with uniformly globoid sclerotia (1-2.2 mm) were observed after 10-12 days of incubation. Based on the morpho-cultural characteristics, the fungus was identified as Sclerotium rolfsii (Mordue, 1974). The identification was confirmed by PCR amplification of ITS-rDNA using ITS1/ITS4 primers (White et al., 1990). The PCR product was sequenced directly and the sequence analysis revealed 100% homology with S. rolf- sii (GenBank accession No. KP412469.1). A representative sequence of S. rolfsii was deposited in GenBank (accession No. KT768140.1). Pathogenicity tests were conducted on 30 healthy leaves by inoculating 2-3 sclerotia from 12 days-old culture. The appearance of necrotic leaf spots was noticed on 22 inoculated leaves seven days post inoculation. No such symptoms were observed on control leaves challenged with water. The fungal pathogen was re-isolated on PDA and its identity confirmed. To the best of our knowledge, this is the first report on the occurrence of S. rolfsii causing leaf spot of J. multiflorum in India.