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First Report of Curvularia lunata Causing Root Rot of Strawberry in India

Diseased strawberry (Fragaria × ananassa Dutch) plants were observed during semimonthly surveys in the Jammu District of Jammu and Kashmir State, India from November 2007 to May 2008. Symptoms included leaf wilt, necrotic roots, and plant death. Small pieces of symptomatic roots were cut from the junction of diseased and healthy tissue, surface sterilized in 0.1% mercuric chloride solution for 1 min, washed in three changes of sterile distilled water, and transferred to potato dextrose agar plates. Cultures were maintained in an incubator at 25 ± 1°C. Dark brown fungal colonies developed in a few days. Mycelium was septate, dark brown-to-blackish brown, and branched. Conidiophores were dark brown, unbranched and septate. Conidia were boat shaped or curved, dark brown, and four-celled with the two central cells larger than the terminal cells. Apical cells were light brown, rounded at the tips, slightly constricted at the base, and 19 to 30 × 9 to 14 μm. The pathogen was identified by the Indian Type Culture Collection, Division of Plant Pathology, Indian Agricultural Research Institute, New Delhi, India (ITCC Accession No. 6680-07) as Curvularia lunata (Wakkar) Boevijn. To conduct pathogenicity tests, 10 healthy runners of strawberry cv. Chandler were planted separately in sterilized pot mix containing loam soil, sand, and peat moss (1:1:1 vol/vol) and allowed to root for a month. Soil near the root zone was then removed to access roots that were gently injured by pricking with a sterilized needle. The soil was replaced after 20 ml of a conidial suspension of 10⁶ conidia/ml of one of the isolates was applied to the roots. Ten healthy strawberry plants grown in noninoculated soil served as controls. After inoculation, the plants were regularly watered. Symptoms similar to those observed in the field developed on all inoculated plants. Roots of the diseased plants turned brown and finally black. Noninoculated plants remained healthy. The pathogen was reisolated from roots of the diseased plants. Curvularia spp. are ubiquitous and are typically considered to be weak pathogens or saprophytes; however they have been reported as minor pathogens of several plants (1,2). Root rot of strawberry caused by Curvularia spp. has been reported (3), but to our knowledge, this is the first report of C. lunata (Wakkar) Boevijn causing root rot of strawberry in India.

References: (1) F. C. Butler. Ann. App. Biol. 40:298, 1953. (2) C. F. Hodges and D. A. Campbell. J. Phytopathol. 143:639, 1995. (3) T. Watanabe et al. Phytopathology 67:1324, 1977.