Field and Greenhouse Screening of Dry Bean Populations for White Mold Resistant Germplasm
April 13, 2004
White mold, caused by Sclerotinia sclerotiorum, is a persistent and economically-damaging disease of dry beans in the Northarvest production area. Growers consistently rank white mold as the most problematic disease in their fields. Essentially all widely-grown dry bean cultivars have some level of susceptibility to the disease. The most efficient way to control plant diseases is through genetic resistance. In previous work by our team, new sources of resistance were identified from dry bean lines from Mexico and Central and South America. Four recombinant inbred (RI) populations, each derived from a different resistant parent crossed to the disease-susceptible cultivar Othello, were developed. Each RI population consists of approximately 120 lines and was developed in such a way that multiple greenhouse and field tests can be conducted to identify desirable lines to use as parents in the breeding program. This year, one population was analyzed in a replicated trial conducted at the mold nursery at the Carrington Research Center in Carrington, ND. This population was misted after inoculation with spores of the white mold fungus to ensure high disease pressure. Segregation for many characteristics (i.e., flowering dates, days to maturity, and so forth) was evident in the population. Consistent with this was segregation for white mold reaction. Most lines had high levels of disease. However, several lines developed considerably less white mold than the susceptible check Othello. Of these, the line 86xO-69 performed particularly well for disease resistance across replications. In addition to this trial, seed of the other three populations were increased in the greenhouse for field planting this year. Each population was also evaluated in the greenhouse this winter (2003-2004) for reaction to white mold to identify lines with putative resistance. A fifth population of dry bean, developed for another purpose, was evaluated in the greenhouse and found to be of potential value for white mold resistance. The best lines from all of these populations, including those tested last summer, will be evaluated in replicated field trials this summer at the Carrington Research Center.