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ThesisItem Restricted Molecular mapping of leaf rust and stripe rust resistance genes transferred from Aegilops speltoides to hexaploid wheat(Punjab Agricultural University, Ludhiana, 2020) Angoth, Sravan Kumar; Chhuneja, ParveenLeaf rust and stripe rust are most serious diseases of wheat worldwide. Utilization of resistance cultivars is an effective and economical method to reduce losses from devastating diseases. Aegilops speltoides with SS genome, has been reported to be a valuable source of resistance genes for leaf rust, stripe rust and stem rust. In present study, inheritance studies and molecular mapping of leaf rust and stripe rust resistance genes were undertaken. Stripe and leaf rust resistant accession of Ae. speltoides was crossed with T. durum cv. Aconchi89. F1 was treated with colchicine and an amphiploid was developed which was selfed 2-3 times to develop stable amphiploid. Aconchi89-Ae. speltoides acc. TA1784 amphiploid was crossed and backcrossed with PBW550 and stable BC2F4 introgression lines were developed. Disease resistant introgression line P33-15 was further crossed with PBW550 for mapping population. In F2 population, 161 plants were segregated in ratio of 3:1 for strip rust and in F2:3 populations, plant were segregated in 1:2:1 ratio for resistant and susceptible for leaf rust at adult plant stage. F3 population genotyping was done by dd-RAD-seq, involves cleaving DNA with two restriction enzymes Sph1 and Mluc1 and by using dDocent pipeline, TASSEL V5.0 raw data was processed for processing steps. SNP were identified between parental genotypes P33-15 and PBW550 and 2118 total SNPs were found be polymorphic which were used for linkage map construction. The chromosomes 1D having minimum and chromosome 3B having maximum number of SNPs. Complete linkage map encompassed a total linkage distance of 17875 cM with a SNP density of 0.12 SNPs/cM. With only 569 SNPs the D genome showed least coverage of 4468.48 cM with a density of 0.127 SNPs/cM. A-genome mapped 660 SNPs while B-genome mapped 824 SNPs. Linkage map was further used for mapping genes/QTL for stripe rust and leaf rust resistance using ICI mapping using BIP function. The phenotypic data of the F2 population and genotypic data of the F3 population were used for mapping the stripe rust resistance loci. The QTL mapping was conducted with LOD threshold of 4.0. Ae. speltoides leaf rust resistance gene was mapped on terminal end of short arm of chromosome 7B at a distance of 26cM from nearest SNP marker S7B_733831709. Overall, one gene each for leaf rust and stripe rust resistance have been introgressed from wild progenitor species Ae. speltoides into hexaploid wheat. A SNP based linkage map consisting of 2118 SNP markers has been developed. A major QTL for stripe rust resistance has been mapped on chromosome 3B and a major gene for leaf rust resistance has been mapped on wheat chromosome 7B. Linked markers can be used for transferring these genes to other wheat backgrounds.
