|Larsen, Karen - ARS FORMER EMPLOYEE|
|Terpstra, Karolyn - MICHIGAN STATE UNIVERSITY|
|Hauf, Darrin - PIONEER HI-BRED INTERNATI|
|Grafton, Kenneth - N DAKOTA STATE UNIVERSITY|
|Kelly, James - MICHIGAN STATE UNIVERSITY|
Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 29, 2007
Publication Date: February 6, 2007
Citation: Miklas, P.N., Larsen, K.M., Terpstra, K.A., Hauf, D.C., Grafton, K.F., Kelly, J.D. 2007. Qtl analysis of ica bunsi-derived resistance to white mold in a pinto x navy bean cross. Crop Science. 47: 174-179. Interpretive Summary: Sclerotinia white mold is a major disease of pinto bean. Fungicides used to control the disease combined with white mold induced yield loss cost pinto bean growers about $25 million annually. Pinto beans generally lack genetic resistance to this disease, but recent progress by ARS scientists in collaboration with scientists from North Dakota State University and Michigan State University have identified a major resistance gene in pinto bean derived from Bunsi navy bean. Resistance was successfully transferred from navy bean to pinto bean using conventional hybridization and selection. Resistance was complexly inherited, but a major gene was identified on linkage group B2. This gene for partial resistance was stably expressed across multiple environments and in different genetic backgrounds will lead to the release of new pinto bean cultivars with improved resistance to devastating white mold disease. In fact, this work has already resulted in the release of a white mold resistant pinto bean germplasm line USPT-WM-1.
Technical Abstract: Breeding for genetic resistance to white mold [Sclerotinia sclerotiorum (Lib.) de Bary] in dry bean (Phaseolus vulgaris L.) is difficult because of low heritability. To facilitate breeding, researchers have sought to identify QTL underpinning genetic resistance to white mold. We identified two QTL conditioning ICA Bunsi-derived resistance to white mold in a pinto x navy bean (Aztec/ND88-106-04) recombinant inbred line (85 RILs) population. ND88-106-04 is a navy breeding line with resistance to white mold derived from ICA Bunsi navy. Aztec pinto is susceptible. The QTL were located to linkage groups B2 and B3 of the core map. The B2 QTL expressed in three of four field environments explaining 24.7, 9.0, and 8.7% of the phenotypic variation for disease severity score. The B3 QTL expressed in two of four environments, explaining 15.7 and 5.3% of the phenotypic variation. The B2 QTL was identified previously in ICA Bunsi x navy and ICA Bunsi x black bean RIL populations. The resistance conferred by the B2 QTL has a physiological basis due to association with stay green stem trait and lack of association with disease avoidance traits. The B3 QTL, undetected in previous studies, was associated with disease avoidance traits (canopy porosity, plant height), stay green stem trait, and maturity. The B2 QTL with stable expression in multiple environments and across genetic backgrounds will be most amenable to manipulation by breeders.