Location: Hard Winter Wheat Genetics Research Unit
Title: Dissection and fine mapping of a major QTL for preharvest sprouting resistance in white wheat rio blanco Authors
|Liu, Shubing -|
Submitted to: Theoretical and Applied Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 17, 2010
Publication Date: July 4, 2010
Citation: Liu, S., Bai, G. 2010. Dissection and Fine Mapping of a Majort QTL for Preharvest Sprouting Resistance in White Wheat Rio Blanco. Theoretical and Applied Genetics. DOI 10.1007/s00122-010-1396-4. Interpretive Summary: Pre-harvest sprouting (PHS) refers to seed germination in a mature wheat spike due to a long period of wet weather. Sprouted wheat grain usually has poor end-use quality. Previously, we identified one quantitative trait locus (QTL), QPhs.pseru-3A, for PHS resistance in white wheat Rio Blanco. This QTL significantly reduced PHS. We found three molecular markers in the QTL region. In this study, we further narrowed down the QTL to a smaller chromosome fragment by developing a new fine-mapping population that segregated only in the chromosome region containing the three markers. The result indicated the QTL in 3A showed single-gene inheritance with partial dominance. Near-isogenic lines (NIL) that differ in having the 3A QTL have been isolated. A high-resolution map in the 3A QTL region was constructed by adding 11 new AFLP markers. This work laid a solid foundation for cloning this gene for sprouting tolerance. This eventually may lead to future cultivars with higher levels of sprouting tolerance.
Technical Abstract: Preharvest sprouting (PHS) is a major constraint to white wheat production. Previously, we mapped quantitative trait loci (QTL) for PHS resistance in white wheat by using a recombinant inbred line (RIL) population derived from the cross Rio Blanco/NW97S186. One QTL, QPhs.pseru-3A, showed a major effect on PHS resistance, and three simple sequence repeat (SSR) markers were mapped in the QTL region. To determine the flanking markers for the QTL and narrow down the QTL to a smaller chromosome region, we developed a new fine-mapping population of 1874 F2 lines by selfing an F6 RIL (RIL25) that was heterozygous in the three SSR marker loci. Segregation of PHS resistance in the F2 population fitted monogenic inheritance. An additive effect of the QTL played a major role on PHS resistance, but a dominant effect was also observed. Fifty-six recombinants among the three SSR markers were identified in the population and selfed to produce homozygous recombinants or QTL near-isogenic lines (NIL). PHS evaluation of the recombinants delineated the QTL in the region close to Xbarc57 flanked by Xbarc321 and Xbarc12. To saturate the QTL region, 11 AFLP markers were mapped in the QTL region with 7 AFLP cosegregated with Xbarc57 by using the NIL population. Dissection of the QTL as a Mendelian factor and saturation of the QTL region with additional markers created a solid foundation for positional cloning of the major QTL.