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First Report of Ascochyta Blight of Chickpea in Latin America

Chickpea (Cicer arietinum L.) has been cultivated in different regions of Bolivia for hundreds of years. In the highlands (2,400 to 3,000 m above sea level) of the Department (state) of Chuquisaca in southern Bolivia, chickpea is an important cash crop for small farmers. During March through April 1999, a blight was observed infecting local chickpea landraces in Chamicle, Escana, Kullpa Ckasa, Presto, Q'ara Puncu, Santa Rosalia, Sucre, and Yotala in Chuquisaca, and its cause was tentatively identified as Ascochyta rabiei (Pass.) Labrousse (teleomorph Didymella rabiei (Kovachevski) v. Arx) based on disease symptomatology. Stems, leaflets, and pods of infected plants exhibited abundant necrotic lesions. Isolations were made from lesions on leaflets, stems, pods, and seeds of infected plants on 2% water agar and potato dextrose agar. The fungus was isolated from the foliar and reproductive tissues of infected plants. Koch's postulates were fulfilled by inoculating the foliage of 15-day-old seedlings of a local chickpea landrace with spore suspensions of three isolates of the pathogen from Escana, Santa Rosalia, and Sucre. Inoculated and control (sterile water) plants were incubated in moist chambers for 4 days in the laboratory at ambient temperatures and under natural daylight. The fungus was reisolated from lesions that developed on the leaflets, petioles, and stems of all inoculated seedlings but not from tissues on any of the noninoculated control plants. The fungus was identified as A. rabiei based on symptoms, cultural and morphological characteristics (2), and pathogenicity tests. Above average rainfall and cool weather during March and April favored development and spread of the disease in many chickpea-growing areas. Severe infection usually resulted in dieback and death of plants and reduced yields. Additionally, A. rabiei was isolated from chickpea seeds purchased in the markets of Sucre and Monteagudo and in seeds used by farmers in Escana to plant the 1999 crop (which had supplied the plants previously observed with blight). The teleomorph did not develop on naturally infested chickpea debris from five locations when incubated over the winter on the soil surface in Sucre. Based on farmers' reports, it appears that Ascochyta blight of chickpea has been present in the Department of Chuquisaca and possibly other Bolivian departments for many years. This is the first report of the disease in either Bolivia or other countries of Latin America (Mexico and Central and South America) (1).

References: (1) CAB. 1991. CAB Distribution Maps of Plant Diseases: Ascochyta rabiei. Map No. 151. CAB International Mycological Institute, Wallingford, England. (2) E. Punithalingham and P. Holliday. 1972. Ascochyta rabiei. Descriptions of Pathogenic Fungi and Bacteria No. 337. Commonwealth Mycological Institute, Kew, England.