Submitted to: Theoretical and Applied Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/1/2004
Publication Date: 1/1/2005
Citation: Xu, X., Bai, G., Carver, B., Shaner, G.E., Hunger, R.M. 2005. Mapping of qtl prolonging latent period of puccinia triticina infection in wheat. Theoretical and Applied Genetics. 110:244-251. Interpretive Summary: Leaf rust in wheat is an important disease in US. It occurs in almost all wheat fields in the US and causes significant yield losses every year. Due to rapid change of pathogen races, single gene resistance is short-lived in wheat cultivars. Slow rusting is considered a crucial component of durable resistance to wheat leaf rust because its effectiveness may not be altered as pathogen races change. Slow rusting is often expressed in the form of prolonged latent period (LP) in which the pathogen needs a longer time from initial infection and to show disease symptoms. Selection for longer LP is considered an effective approach to develop wheat cultivars with improved durable resistance to leaf rust. A recombinant population derived from the line CI 13227 was analyzed with molecular markers. One gene on chromosome 2DS was identified having a major effect on prolonging the latent period of the rust fungus. Two other genes on 2B and 7B also affected latent period. The three genes collectively explained 73.8% of the genetic effect on LP. Three molecular markers linked to the three genes have potential to be applied in marker-assisted selection for prolonged latent period in wheat.
Technical Abstract: Slow rusting is considered a crucial component of durable resistance to wheat leaf rust caused by Puccinia triticina, and is often expressed in the form of prolonged latent period (LP). Selection for longer LP is considered an effective approach to develop wheat cultivars with improved durable resistance to leaf rust. A recombinant inbred line (RIL) population derived from CI 13227 (long LP) x Suwon 92 (short LP) was phenotyped for LP in two greenhouse experiments in two years, and AFLP and SSR markers were analyzed in the same population. Among the RILs, the frequency distribution for LP was continuous, and LP was highly correlated between years (r=0.94, p<0.0001). A QTL prolonging the latent period of Puccinia triticina, designated as QLrlp.osu-2DS, explained 42.6 and 54.4% of the phenotypic and genetic variance across two experiments, respectively. QLrlp.osu-2DS was mapped on the distal region of chromosome 2DS. Two other QTL for latent period, QLrlp.osu-2B and QLrlp.osu-7BL, were localized on chromosome 2B and the long arm of chromosome 7B, respectively. Multiple regression analysis showed that these three QTL collectively explained 58.0 and 73.8% of the phenotypic and genetic variance over two experiments, respectively. Fourteen RILs with all three long LP alleles at three AFLP loci flanking QLrlp.osu-2DS, QLrlp.osu-2B, and QLrlp.osu-7BL had a mean LP of 12.5 days, whereas 13 RILs without any long LP alleles at the corresponding loci had a mean LP of 7.4 days. Three SSR markers closely linked to these QTL have potential to be applied in marker-assisted selection for prolonged latent period in wheat.