Reaction of a Bean Germplasm Collection Against Five Races of Colletotrichum lindemuthianum Identified in Northern Spain and Implications for Breeding.

Anthracnose, caused by Colletotrichum lindemuthianum, is one of the most serious diseases of common bean (Phaseolus vulgaris). The pathogenic variability of this fungus in northern Spain and the response of a bean germplasm collection maintained at Servicio Regional de Investigación y Desarrollo Agroalimentario (Villaviciosa, Asturias, Spain) were screened in order to identify potential resistance sources. Races 3, 6, 19, 38, and 102 were identified from 55 isolates collected in this area, race 38 being the most common one. In all, 246 landraces and 42 lines derived from breeding programs were evaluated in search of resistant lines. No local accession showed adequate resistance to the five races. However, three local accessions were resistant to four races and presented intermediate or mixed reactions against the fifth one: accession V225, with a large great northern seed phenotype (RRIRR); accession V369, with a great northern seed phenotype (RRRRR/S); and accession V309, with a navy seed phenotype (RRRR/SR). The results revealed a wide variation in the resistance spectra or resistance combinations, although not all the possible resistance spectra were present in the evaluated accessions. Among the breeding lines, nine materials were resistant to five races and three lines (A252, A321, and A493) were selected as resistance sources to transfer genetic resistance to Andecha bean cultivar. The results indicated that lines A252 and A321 have two dominant and independent genes involved in the resistance to race 38 whereas line A493 has a single locus.