Fine Mapping and identification of candidate gene(s) for leaf rust and stripe rust resistance introgressed in Triticum aestivum L. from Aegilops peregrina
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Date
2017
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Punjab Agricultural University, Ludhiana
Abstract
Ae. peregrina acc. pau 3519, a non-progenitor species (UUSS) maintains high level of resistance to leaf
and stripe rust. Two sets of homozygous WL711-Ae. peregrina introgression lines (ILs) viz. IL
pau16061 harboring LrAp and IL pau16058 harboring LrP–YrP were crossed with wheat cv. WL711 to
generate mapping populations. Inheritance studies, fine mapping of rust resistance genes with SNP/STS
markers and identification of candidate genes through Resistance Gene Enrichment Sequencing (RenSeq)
were undertaken in the present investigation. F2.3 population of WL711/ IL pau16058 segregated into 260
resistant: 517 segregating: 226 susceptible (χ21:2:1=3.26) against leaf rust and 257 resistant: 520
segregating: 226 susceptible (χ21:2:1=3.281) against stripe rust races indicating transfer of two dominant
co-segregating rust resistance genes. In the initial analysis, LrP–YrP genes were mapped on 5DS showing
linkage with XLr57/Yr40–CAPS16, Xbarc130 and XTa5DS_44573. High resolution genetic map spanning
4.28cM including eight SNP markers, one SSR and two STS markers was generated. Marker loci
BS00163889 flanked distally (co-segregating) and gsnp_5ms_4641 proximally (seven recombinants) to
LrP–YrP. SNP markers designed from nucleotide binding and leucine rich repeats (NLRs) depicting
independent variations in mutants were placed away from LrP–YrP. Inheritance studies on F6 RILs of
WL711/IL pau16061 indicated transfer of a single major dominant gene conditioning seedling resistance.
In initial analysis, GISH on IL pau16061 established that LrAp has been introgressed from the Sp genome
of Ae. peregrina to the long arm of a pair of homoeologous chromosomes of wheat. Bulked Segregant
Analysis (BSA) placed the alien segment onto chromosome 2BL as indicated by linkage of LrAp with
markers Xncw-Lr58-1 and Xcfd50. For fine mapping of LrAp, five co-dominant SNP markers and one
dominant marker based on presence/absence variations were designed directly from NLRs. These markers
positioned the LrAp gene distally on the alien segment and indicated homology with the 6BL
chromosome of wheat. The marker Ren_1191 showed co-segregation with LrAp. Linkage of both 2BL
and 6BL specific markers with LrAp indicated translocation of a 6Sp alien segment onto the long arm of
wheat chromosome 2B. The identification of co–segregating markers for LrAp and LrP–YrP in the
present study will facilitate marker–assisted pyramiding with other genes.
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