First Report of Ascochyta Blight of Chickpea Caused by Ascochyta rabiei in Chile

Abstract

Chickpea (Cicer arietinum L.) plants with foliar and stem lesions fitting the description of Ascochyta blight were observed in October 2002 in four chickpea crops located in the La Araucania Region (38°S, 72°24′W) in southern Chile. Large, circular foliar and stem lesions containing pycnidia arranged in concentric circles were observed (1). Stem breakage also was observed. Isolates were obtained from mature pycnidia developed on stems by culturing a spore suspension on potato dextrose agar (PDA) and chickpea seed meal agar. A pathogenicity test was performed by inoculating 25 plants with a suspension of 1.2 × 105 conidia ml-1 and incubating at 22°C and 75% relative humidity. Foliar and stem lesions were observed 5 and 7 days after inoculation, respectively. Four check plants sprayed with sterile distilled water showed no symptoms. Fungal colonies obtained from inoculated plants showed the same cultural characteristics as the original isolates. Cultural morphology was consistent with the description of Ascochyta rabiei (Pass.) Labrousse (teleomorph Didymella rabiei (Kovacheski) v. Arx (= Mycosphaerella rabiei Kovacheski)) (3). Conidia produced on PDA were predominantly aseptate, 3.90 to 5.85 μm wide, and 9.75 to 11.7 μm long. Affected plants (cv. Kaniva) originated from seed introduced at commercial volumes (69 ton) from Victoria, Australia in August 2002. A. Rabiei can be disseminated via infected seed (1). Ascochyta blight symptoms also have been observed in small patches in several crops near Temuco, the capital of the La Araucania Region. Chickpea production is currently, relatively small in southern Chile, however, plans to promote its cultivation may be hindered by this outbreak. Previously, the only other country to report Ascochyta blight of chickpea in South America was Bolivia (2). References: (1) W. J. Kaiser. Epidemiology of Ascochyta rabiei. Pages 117–134 in: Disease-resistance Breeding in Chickpea. K. B. Singh and M. C. Saxena, eds. ICARDA, Aleppo, Syria, 1992. (2) W. J. Kaiser et al. Plant Dis. 84:102, 2000. (3) E. Punithalingam and P. Holliday. No. 337 in: CMI Descriptions of Pathogenic Fungi and Bacteria. CMI, Kew, Surrey, UK, 1972.