Field Crop Studies, (2006) 3 (4):623-627
Ivan Kiryakov, and Dimitar Genchev
Dobroudja Agricultural Institute, 9520, General Toshevo, Bulgaria
ABSTRACT
In common bean, alleles at locus Co-1 provides resistance to Middle America (MA) races of Colletotrichum lindemuthianum, among them being race 81, which is widespread in Bulgaria. Up to now four alleles have been identified at the locus Co-1. Three of them were present in the differential cultivars “MDRK” (Co-1), “Perry Marrow” (Co-13) and “Kaboon” (Co-12). Races 6 and 2 of the fungus were virulent to the alleles present in the first two varieties. This study considers the reaction of 190 common bean accessions to races 81, 6 and 2 of C. lindemuthianum with the aim to select cultivars and lines possessing alleles Co-1 and Co-13. The plants were grown in a greenhouse at 20-25C day temperature and 18-20C night temperature. Plants were sprayed with spore suspension 106 spores/ml seven days after germination. Spore mass of one isolate from each race of the fungus - 81, 6 and 2, was used as inoculum. Following inoculation, plants were transferred to a moist chamber for 72 hours at 20-22/16-190C day/night temperature. Disease reaction was read 7-10 days after inoculation according to a 9-degree scale: 1-3 - resistant, 5-9 - susceptible. Twenty-six of the investigated accessions demonstrated resistance to race 81. Accessions “IIRR 7585”, “Trudovets” and “Vranya 1” were susceptible to races 2 and 6; this is an indication that their resistance to race 81 is controlled by allele Co-1. Cultivars “Laker”, “Montcolm”, “Mecosta” and “Red Hawk”, and lines “SEQ 1005” and “ICA Linea 64” were susceptible to race 6 and resistant to race 2. These results showed that their resistance to race 81 is controlled by allele Co-13. The above accessions are suitable donors for resistance to the MA races of the fungus widespread in Bulgaria.