Submitted to: Proceedings of the International Sclerotinia Workshop
Publication Type: Proceedings
Publication Acceptance Date: December 1, 2001
Publication Date: January 1, 2002
Citation: MIKLAS, P.N. MARKER ASSISTED BACKCROSSING OF TWO WHITE MOLD RESISTANT QTL INTO SUSCEPTIBLE PINTO BEAN: I. EARLY GENERATION ASSESSMENT. PROCEEDINGS OF THE INTERNATIONAL SCLEROTINIA WORKSHOP, Vol. 1, p. 4. 2002. Technical Abstract: Research was conducted in 2002 to assess the effectiveness of marker-assisted selection for transferring white mold resistance conditioned by quantitative trait loci (QTL) into the susceptible pinto bean market class. The QTL, with expression in both the greenhouse straw test and field, derive from different sources: G122, a large-seeded landrace from India, and NY6020-4, a snap bean breeding line from Cornell University. The QTL from G122 and NY6020-4 reside on different linkage groups, B7 and B8, respectively. Tightly linked DNA markers (SCARs and RAPDs) were used to introgress the QTL into susceptible pinto bean. Three marker-assisted backcrosses (BC) were conducted to transfer the QTL from the donor parents to the recurrent pinto bean cultivars Winchester (B7 QTL) and Maverick (B8 QTL). Three populations (Pop-1, Pop-2, Pop-3), each consisting of about 45 BC3F2 plants, were evaluated for reaction to white mold in the straw test and assayed for presence of the QTL-linked SCAR markers. The marker linked with the B7 QTL explained 15% (P = 0.02) of the phenotypic variation for disease resistance among F2 individuals segregating in Pop-1 as measured by lesion length (mm), and explained 12% (P = 0.03) of the variation as measured by disease score (rated from 1 to 9) in Pop-2. The B8 QTL-linked marker explained 19% (P = 0.002) of the phenotypic variation for disease score in Pop-3.