In the Stranja Mountains of southeastern Bulgaria, native populations of Cicer montbretii Jaub. & Spach were found on the edge of a road in an oak forest near the village of Gramatikova (42°1′38″N; 27°36′49″E) at an elevation of about 125 m. C. montbretii, a perennial species, is the only wild Cicer sp. native to Bulgaria. At the time of collection, necrotic lesions were observed on the stems, leaflets, and pods of several plants, and these lesions were reminiscent of those induced by Ascochyta rabiei (Pass.) Labrousse. The teleomorph (sexual stage) of A. rabiei, Didymella rabiei (Kovachevski) v. Arx (syn. Mycosphaerella rabiei Kovachevski), was discovered in 1936 on overwintered chickpea residue in southern Bulgaria. The fungus is heterothallic and requires the pairing of two compatible mating types for development of fertile pseudothecia. Both mating types of A. rabiei were isolated previously from naturally infected, cultivated chickpeas (C. arietinum L.) from northeastern and southern Bulgaria (1), and the teleomorph, Didymella rabiei (Kovachevski) v. Arx, developed on naturally infested chickpea debris from both regions when it was incubated at appropriate environmental conditions. Isolations were made from lesions on the leaflets, stems, pods, and seeds of C. montbretii by surface disinfecting tissue in 0.25% NaOCl for 5 min, drying on paper hand towels, and placing small pieces of tissue on 2% water agar and Difco potato dextrose agar. Plates were incubated at 22 to 24°C under fluorescent lights with a 12-h photoperiod. A. rabiei was isolated from all foliar tissues of the plant, including seeds. Koch's postulates were fulfilled by inoculating the foliage of chickpea PI 458870 and reisolating the fungus from lesions that developed on the leaflets and stems. Six Bulgarian isolates of A. rabiei from C. montbretii were paired with compatible mating type tester isolates of A. rabiei, MAT1-1 (ATCC 76501) and MAT 1-2 (ATCC 76502), following the procedure of Kaiser and Kusmenoglu (2). Both mating types were found among the six isolates. Two were MAT 1-1 and four MAT 1-2. The teleomorph did not develop on the small amount of naturally infested chickpea residue tested. Therefore, in Bulgaria, both cultivated and wild chickpeas are infected naturally by A. rabiei and both mating types have been isolated from these hosts. D. rabiei will likely be found in native stands of C. montbretii in Bulgaria as more samples of overwintered infested debris are examined for the teleomorph. This is the first report of A. rabiei causing blight of a wild Cicer sp.
References: (1) W. J. Kaiser. Can. J. Plant Pathol. 19:215, 1997. (2) W. J. Kaiser and I. Kusmenoglu. Plant Dis. 81:1284, 1997.