Submitted to: Theoretical and Applied Genetics
Publication Type: Peer reviewed journal
Publication Acceptance Date: 4/10/2008
Publication Date: 4/10/2008
Citation: Wu, X., Blake, S., Sleper, D.A., Shannon, J.G., Cregan, P.B., Nguyen, H.T. 2008. QTL and Additive and Epistatic Effects for SCN Resistance in PI 437654. Theoretical and Applied Genetics. 118:1093-1105. Interpretive Summary: The soybean cyst nematode (SCN) is a major problem in soybean production in the USA causing upwards of $1 billion in damage to the crop each year. Planting SCN-resistant soybean cultivars is the most cost effective control method. PI 437654 is a unique soybean accession because of its resistance to nearly all SCN races. The objectives of this study were to confirm and refine the locations of genes associated with SCN resistance in PI 437654. Using molecular genetic markers we confirmed and refined the locations of four previously identified major SCN resistance genes or “quantitative trait loci” (QTLs) at four different positions on the soybean chromosomes. We also detected some new QTLs that controlled resistance to a number of different races of the SCN. This information will be of use to soybean breeders who are developing new soybean cultivars with resistance to the SCN.
Technical Abstract: The soybean cyst nematode (SCN), Heterodera glycines Ichinohe, is a major problem in soybean production in the USA. Planting SCN-resistant soybean cultivars is the most cost effective control method. PI 437654 is a unique accession because of its resistance to nearly all SCN HG types (races). The objectives of this study were to confirm and refine the locations and gene actions associated with SCN resistance previously discovered in PI 437654, and to identify new QTLs that may have been missed in previous studies because of low coverage with the genetic markers used. Using 205 F12 RILs and 276 SSR and AFLP molecular markers covering 2406.5 cM of 20 linkage groups (LGs), we confirmed and refined the locations of major SCN resistance QTLs on LG-B1, -A2, and -G previously identified in PI 437654 or other resistant sources. We found that these major QTLs have epistatic effects among them or with other loci for SCN resistance. We also detected some new QTLs with additive or epistatic effects for SCN resistance to different HG types (races) on almost all LGs except LGs-B2 and -D1b. The QTL on LG-G was associated with resistance to races 1, 2, 3, and 5, and it contributed a large proportion of the additive effects. The QTL on LG-A2 was associated with resistance to races 1 and 3. The QTL on LG-B1, associated with resistance to races 1, 3, and 5, was confirmed and was similar to QTLs found in PI 90763 and PI 404198B. In addition to QTL on LGs -A2, -B1 and -G, a novel additive QTL without any epistatic effect, associated with SCN resistance to race 3, 5, and 14, was identified on LG-I, located in the BARC-Sat_299 – BARC-Sct_189 region. Moreover, several minor QTLs on LGs-C1, D1a, H and K were found to be associated with SCN resistance to individual races. By evaluating another RIL population with a different genetic background, confirmation of the new SCN resistance QTL is underway.