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First Report of Fusarium equiseti Causing Vascular Wilt of Cumin in India

Cumin (Cuminum cyminum) is one of the important spices in the world after black pepper. Cumin is mainly used in flavoring foods for its distinctive aroma and ayurvedic medicines. The production of cumin seeds in India is estimated to be around 0.15 million tons annually. Wilt symptoms were observed on field-grown cumin during the winter of 2009 and 2010. Diseased plants exhibited symptoms including wilted leaves, stunted growth, and eventually, death. In severe cases, approximately 65% of the plants in the field died. Isolations of the pathogen were made from the discolored tissues on potato dextrose agar (PDA) and Rose Bengal after disinfestations in 0.1% HgCl₂ for 2 min and dipping in 70% ethanol for 10 s. Petri dishes were then incubated in complete darkness at 26°C for 7 days. Typical growth characters observed were development of abundant white aerial mycelium that turned peach orange by incubating under light. Microconidia were single-celled, hyaline, non-septate and ovoid, and ranged from 9.5 to 12.5 × 3.5 to 5.25 μm. Macroconidia were mostly two- to three-septate, slightly curved at apex, and ranged from 28.0 to 30.5 × 3.5 to 5.25 μm. The fungus was identified as Fusarium equiseti based on colony characters and spore morphology (3). The identity was further confirmed by the Fungal Identification Service, Mycology and Plant Pathology Group Agharkar Research Institute, Pune, India (Accession No. NFCCI-2157). The ITS (internal transcribed spacer) region of rDNA was amplified by polymerase chain reaction (PCR) with primers ITS1/ITS2 and sequenced (2). BLASTn analysis of the sequence obtained showed a 99.78% homology with F. equiseti at NCBI and FUSARIUM-ID v. 1.0 (1). The sequence was deposited at GenBank (Accession No. JN014954). Pathogenicity tests were conducted on 10 healthy 1-month-old seedlings of cumin in a moist chamber. Plants were separately inoculated in pots with sterilized soil and 10 ml of F. equiseti isolate spore suspension (107 conidia/ml) at 25°C for 7 to 10 days. Control plants were inoculated with sterile soil without spore suspension. Within 10 days, inoculated plants developed leaf wilt, stunted growth, discolored vascular tissue on stems, and finally died, which is similar to that observed in the field. Control seedlings were symptom free. Koch's postulates were fulfilled by reisolating the fungal pathogen, which was identified as F. equiseti causing vascular wilt on cumin reported in Israel (4). However; F. oxysporum f. sp. Cumini is the first reported vascular wilt of cumin. To our knowledge and on the basis of the literature, this the first report of vascular wilt of cumin caused by F. equiseti in India.

References: (1) D. M. Geiser et al. Eur. J. Plant Pathol. 110:473, 2004. (2) M. Korabecna. In: Communicating Current Research and Educational Topics and Trends in Applied Microbiology, p. 783, 2007. (3) J. F. Leslie and B. A. Summerrell. The Fusarium Laboratory Manual. Blackwell Publishing, Ames, IA, 2006. (4) R. Reuveni. Plant Dis. 66:498, 1982.