First report of leaf blight of physic nut caused by Curvularia clavata in India.

Abstract

Physic nut (Jatropha curcas L.) is an important commercial bio-diesel plant. In a survey carried out during 2011 in Tamil Nadu (India), physic nuts plants were observed exhibiting leaf yellowing, chlorotic or necrotic spots and greyish-brown spots, predominantly on leaf margin. Infected leaf portions cut into small fragments (1 cm2) were surface-sterilized in 0.1% mercuric chloride for 30 sec, washed three times in sterile distilled water, plated on potato dextrose agar (PDA) medium containing streptomycin sulphate, and incubated at room temperature (28±2°C) for five days. Ten single-spore isolates of a fungus recovered from infected tissues were maintained on PDA slants. Pathogenicity was tested by artificially inoculating (pinprick method) the leaves of 45-day-old glasshouse-grown host plants with a spore suspension (5x105 spores ml-1) (Rao et al., 1991). Inoculated plants were maintained in glasshouse at 25-28°C, RH above 90%, and 12 h photoperiod. Symptoms similar to those observed in the field were detected two weeks post inoculation and the fungus was consistently reisolated from leaf lesions. Conidia were clavate, 3-septate, straight or occasionally slightly curved, with base cell pale brown, while the other cells were brown to dark brown, 17-29 (23) μm long, 7.2-12 (8) μm thick in the broadest part, sometimes truncate at the base. The fungus was identified as Curvularia clavata and confirmed by the Agarkar Mycological Research Institute, Pune, India (NFCCI 2673). C. clavata infects monocot and dicot plants causing an array of symptoms including leaf spot and leaf blight (Chen et al., 2013). To our knowledge, this is the first report of leaf blight caused by C. clavata on physic nut in India.