Pyramiding white mould resistance between and within common bean gene pools

Abstract

Singh, S. P., Schwartz, H. F., Terán, H., Viteri, D. and Otto, K. 2014. Pyramiding white mould resistance between and within common bean gene pools. Can. J. Plant Sci. 94: 947–954. White mould caused by Sclerotinia sclerotiorum (Lib.) de Bary is a severe disease of common bean (Phaseolus vulgaris L.) in North America and similar production regions. Low to high levels of white mould resistance exist in cultivated and wild common bean and the secondary gene pool. But, cultivars with high levels of resistance are not yet available. The objectives of this study were: (1) to combine or pyramid high levels of resistance from multiple-parent populations between and within gene pools, and (2) to compare the response of pyramided breeding lines (PBL) to four isolates of the white mould pathogen with that of known sources of resistance. Two Andean PBL each derived from an Andean intra-gene pool and inter-gene pool, four Middle American pinto bean PBL from one inter-gene pool multiple-parent population, their seven resistant parents, and susceptible pinto, Othello, were inoculated in the greenhouse with pathogen isolates ARS12D and ND710 at University of Idaho, Kimberly in 2012, and isolates CO467 and NY133 at Colorado State University, Fort Collins in 2013. The percentage of resistant plants for the PBL ranged from 62.5 to 81.9, and mean white mould score from 4.0 to 4.6. The respective values for the white mould resistant parents ranged from 3.1 to 57.0 for the percentage of resistant plants and from 4.8 to 7.5 for the mean white mould score. Furthermore, PBL SE154-1 inoculated with isolate ARS12D, and SE152-6 with isolates ARS12D and ND710 had 100% resistant plants. But, only SE153-1 and SE155-9 inoculated with isolates CO467 and NY133 had significantly (P ≤0.05) higher levels of resistance than the most resistant parents A 195 and VA 19. The pinto bean PBL SE153-1, SE153-6, and SE153-7, and Andean types SE152-6 and SE155-9 were the most resistant among all genotypes inoculated with the four isolates of the white mould pathogen in both greenhouses.