FIRST REPORT OF LEAF BLIGHT CAUSED BY MACROPHOMINA PHASEOLINA ON JASMINIUM MULTIFLORUM IN INDIA
S. Mahadevakumar, G.R. Janardhana
Jasminium multiflorum is an important flower crop grown extensively in South India. A characteristic leaf blight symptom was observed during a field survey conducted during September–December, 2014. The disease incidence was 16% over about 62 ha of crop fields visited. The disease started with small necrotic spots (2-5 mm) at the margin of leaf the lamina to spread all along the leaf midrib. Pycnidia were observed on the blight-affected leaves. Symptomatic leaf fragments (0.5 cm) were surface-sterilized with 2% NaOCl, placed on potato dextrose agar (PDA) and incubated at 28±2°C. Fungal colonies formed many dark sclerotia (65- 152 x 35-98μm) after 10-12 days of incubation. Pycnidia that developed on necrotic tissues measured 182-210 μm and contained single-celled conidia (15-19-5-7μm). Based on these traits, the fungal pathogen was identified as Macrophomina phaseolina. This identification was confirmed by PCR amplification of ITS-rDNA using ITS1/ITS4 primers (White et al., 1990). The PCR product was sequenced directly (GenBank accession No. KT7681134.1) and the sequence analysis revealed 99% homology with M. phaseolina (JX945170.1 and FJ395221.1). Pathogenicity tests were conducted on 30 healthy 70-days-old plants by foliar application of conidial suspension (1x105 conidia/ml). Leaf blight symptoms were noticed on 16 inoculated plants 10 days post-inoculation. No symptoms were observed on control leaves inoculated with water. The fungus was re-isolated on PDA and its identity was confirmed. To the best of our knowledge, this is the first report on the occurrence of leaf blight disease on J. multiflorum caused by M. phaseolina in India.