Abstract
Abstract A description is provided for Ascochyta phaseolorum [Phoma exigua var. exigua] . Information is included on the disease caused by the organism, its transmission, geographical distribution, and hosts. HOSTS: On Canavalia ensiformis, Glycine max, Lablab (Dolichos) niger, Phaseolus acutifolius, P. atropurpureus, P. aureus, P. calcaratus, P. lathyroides, P. limensis, P. lunatus, P. mungo, P. nanus, P. richardianus, P. trilobus, P. vulgaris, Vigna catjang', V. coerulea, V. sesquipedalis, V. sinensis, V. unguiculata, Voandezia subterranea . Also by inoculation on Althaea rosea, Cannabis sativa, Capsicum annuum, Fagopyrum sagittatum, Gossypium spp., Hibiscus esculentus, Lycopersicon esculentum, Malva verticillata, Nicotiana tabacum, Solanum melongena, Vicia sativa (Crossan, 1958; Zherbele, 1958). DISEASE: Leaf spot (or blotch) of bean. Young leaf spots are irregularly circular with grey to brown centres surrounded by a border of light green-yellow tissue. Other spots are light to dark brown and frequently zonate, marginal, terminal or discrete, cracking in the centre when the dead tissue finally drops out, 3-5 cm diam. Lesions common on pulvini result in considerable defoliation. Ascochyta phaseolorum causes target-spot lesions on several genera in the Leguminosae . Such symptoms on Phaseolus spp. are indistinguishable from the drab, zonate lesions of A. boltshauseri , but are distinct from those of A. pinodella L. K. Jones which are purplish-brown, indistinctly zonate and irregular, and A. pisi Lib. which are not zonate but light brown with a darker distinct margin. Also destructive on pods, stems and roots of seedlings. GEOGRAPHICAL DISTRIBUTION: Africa (Congo, Ethiopia, Kenya, Malawi, Rhodesia, Sudan, South Africa, Tanzania, Uganda, Zambia); Asia (China, India, Japan, Malaya, North Borneo, Pakistan, Sarawak), Australasia & Oceania (New Guinea, Solomon Is.); Europe (Denmark, Great Britain, Czechoslovakia, Netherlands, Sweden, U.S.S.R.); North America (U.S.A.); South America (Peru). TRANSMISSION: Seed borne, persisting in a viable condition for 24 years (26: 276). Viability and virulence also unimpaired after storage in culture at 1°C or 10-12°C for 20-25 months (41: 374). The pathogen may spread by infected haulms and by spores disseminated by splashing rain drops from infected seedlings. Also spread in pods of harvested plants stored in stooks in the field in cool, moist, weather (Hubbeling, 1955).
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