Characterization of Colletotrichum lindemuthianum Races in Zambia and Evaluation of the CIAT Phaseolus Core Collection for Resistance to Anthracnose.

Abstract

Colletotrichum lindemuthianum, the causal pathogen of common bean (Phaseolus vulgaris) anthracnose, is highly variable. Therefore, understanding its race structure and identification of new sources of resistance is necessary for the development of varieties with durable resistance. The objectives of this study were (i) to characterize isolates of C. lindemuthianum collected from three major bean-growing regions in Zambia and (ii) evaluate the International Center for Tropical Agriculture (CIAT) Phaseolus core collection for resistance to C. lindemuthianum races 37, 73, and 566 and a blend of 20 races. Isolates collected from three major bean-growing districts in Zambia, namely Mporokoso, Mpika, and Mbala, were characterized as races 37, 73, and 566, respectively. A subset of the CIAT core collection comprising 885 accessions of common bean, 13 accessions of scarlet runner bean (Phaseolus coccineus), and 11 accessions of year bean (Phaseolus dumosus) was evaluated for resistance to races 37, 73, and 566 and a blend of 20 races in a greenhouse at the University of Zambia, Lusaka, Zambia. Totals of 72, 66, 48, and 9% of P. vulgaris accessions evaluated were highly resistant to races 37, 73, and 566 and a blend of 20 races, respectively. Also, accessions of P. coccineus and P. dumosus highly resistant to races 37, 73, and 566 were identified. Only eight of the 331 P. vulgaris accessions were highly resistant to all three individual races (37, 73, and 566) and to a blend of 20 races. These eight accessions constitute a valuable breeding resource for developing varieties with durable resistance to C. lindemuthianum.