Identification and comparative mapping of a powdery mildew resistance gene derived from wild emmer (Triticum turgidum var. dicoccoides) on chromosome 2BS

Abstract

Powdery mildew, caused by Blumeria graminis f. sp. tritici, is an important foliar disease of wheat worldwide. Wild emmer (Triticum turgidum var. dicoccoides) is a valuable genetic resource for improving disease resistance in common wheat. A powdery mildew resistance gene conferring resistance to B. graminis f. sp. tritici isolate E09 at the seedling and adult stages was identified in wild emmer accession IW170 introduced from Israel. An incomplete dominant gene, temporarily designated MlIW170, was responsible for the resistance. Through molecular marker and bulked segregant analyses of an F(2) population and F(3) families derived from a cross between susceptible durum wheat line 81086A and IW170, MlIW170 was located in the distal chromosome bin 2BS3-0.84-1.00 and flanked by SSR markers Xcfd238 and Xwmc243. MlIW170 co-segregated with Xcau516, an STS marker developed from RFLP marker Xwg516 that co-segregated with powdery mildew resistance gene Pm26 on 2BS. Four EST-STS markers, BE498358, BF201235, BQ160080, and BF146221, were integrated into the genetic linkage map of MlIW170. Three AFLP markers, XPaacMcac, XPagcMcta, XPaacMcag, and seven AFLP-derived SCAR markers, XcauG2, XcauG3, XcauG6, XcauG8, XcauG10, XcauG20, and XcauG25, were linked to MlIW170. XcauG3, a resistance gene analog (RGA)-like sequence, co-segregated with MlIW170. The non-glaucousness locus Iw1 was 18.77 cM distal to MlIW170. By comparative genomics of wheat-Brachypodium-rice genomic co-linearity, four EST-STS markers, CJ658408, CJ945509, BQ169830, CJ945085, and one STS marker XP2430, were developed and MlIW170 was mapped in an 2.69 cM interval that is co-linear with a 131 kb genomic region in Brachypodium and a 105 kb genomic region in rice. Four RGA-like sequences annotated in the orthologous Brachypodium genomic region could serve as chromosome landing target regions for map-based cloning of MlIW170.

In silico cloning and chromosomal localization of EST sequences that are related to leaf senescence using nulli-tetrasomes in wheat

“…We further determined the chromosomal location of 5 polymorphic ESTs (Table S1), and there were complete differences in the genomic and chromosomal locations using the Chinese Spring nullisomic-tetrasomic lines compared to those using in silico mapping. However, in the past, ESTs were believed to be conserved portions of expression genes, which are used as the theoretical basis for comparative genomics analyses (Liu et al 2012). This result warns plant breeders and researchers that the homology analysis and comparative genomics analysis results are not reliable.…”

Fine Physical and Genetic Mapping of Powdery Mildew Resistance Gene MlIW172 Originating from Wild Emmer (Triticum dicoccoides)

“…Comparative genomics analyses can be used to exploit the syntenic relationships among grass species for development of new markers linked to genes of interest by analyzing well-assembled genome sequence information available in model species [7], [62]. Nevertheless, many studies have reported poor levels of micro-colinearity between wheat and rice because of inversions, deletions, duplications, and other rearrangements [6], [7], [48], [63].…”

“…Nevertheless, many studies have reported poor levels of micro-colinearity between wheat and rice because of inversions, deletions, duplications, and other rearrangements [6], [7], [48], [63]. The isolation of the wheat disease resistance genes Lr10 , Lr21 and Pm3 has also shown that wheat and rice have very limited colinearity in the relevant chromosomal regions.…”

“…Isolate E09 is virulent on Pm1a , Pm3a , Pm3c, Pm5a , Pm6 , Pm7 , Pm8 , Pm17 and Pm19 [7], but avirulent on IW172. The E09 isolate was used to test the resistance of Mo75, IW172, F 1 , F 2 plants and F 2:3 progenies at the seedling stage under controlled greenhouse conditions.…”

Localization of the powdery mildew resistance gene Pm07J126 in wheat (Triticum aestivum L.)

“…These provide new opportunities for genome analysis and gene mapping. For example, Yr26 (Zhang et al 2013), Ml3D232 (Liu et al 2012), Eps-3A m (Gawroński and Schnurbusch 2012), PmAS846 (Xue et al 2012), and Pm6 (Qin et al 2011), have been finely mapped based on collinearity between wheat, rice and Brachypodium.…”