Farmer crop variety mixtures to cope with disease epidemics in the common bean cropping system of the Ecuadorian highlands

Abstract 1. Common bean variety mixture diversity: a farmers and scientific view of its contribution to the highlands agroecosystem sustainability in Ecuador. Common bean has been for long time the most cultivated legume for direct consumption in Ecuador. It is still cultivated mostly in traditional agroecosystems, in which farmers have implemented a series of management strategies to maintain crop sustainability. By linking participatory diagnosis, crop diversity assessment, and disease evaluation in the field, we established rationality of famers’ practices for the climbing common bean cropping system in the highlands of Ecuador. Climbing common bean is primarily grown intercropped with maize in a variety mixture strategy involving high genetic diversity. Two different types of variety mixtures are intercropped with maize in Cotacachi (north Ecuador): Chacra, a late maturing type of growth habit IV and Allpa an early maturing type of growth habit I, II, and III. In Saraguro (south Ecuador), only Chacra variety mixtures are cultivated; however, Popayán (Phaseolus coccineus) is often part of Chacra variety mixtures. Common bean cultivation in the intensified approach in Cotacachi and Saraguro aims food security by a better food provision of Chacra and Allpa types along the year, and by buffering biotic and abiotic constraints, which is achieved by planting genetically diverse variety mixtures. A negative association was observed between variety mixtures richness and evenness with rust epidemics. Farmers were knowledgeable about mixture diversity, mixture benefits, and pest and disease epidemics. They were able to name in an analytical way most components of variety mixtures, they perceived inter-specific diversity (intercrop) and intra-specific diversity (variety mixtures) reducing pest and diseases epidemics. Farmers also perceived evident differences among diseases, disease transmission, and disease resistance and its durability. However, as expected and reported frequently in literature, farmers associated disease origin with disease conducive conditions such as rain and clouds. Resistance and its durability are for farmers closely associated traits; resistant for farmers is absence of disease, which was easily detected in Phaseolus coccineus, which is a case of nonhost resistance or marginal host.