Fine mapping and identification of candidate genes for stripe and leaf rust resistance transferred from Aegilops umbellulata to bread wheat (Triticum aestivum)
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Date
2017
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Punjab Agricultural University, Ludhiana
Abstract
Leaf rust and stripe rust are the most damaging diseases of wheat worldwide. Due to domestication and breeding, the narrow genetic base of modern cultivars makes it difficult to combat the changing environmental conditions as well as the emerging new pathogens. To broaden its genetic base, hybridization with wild relatives, landraces and early domesticates is widely used as they harbor rich genetic diversity. In the present investigation, Lr76 and Yr70 transferred from Ae. umbellulata to bread wheat were fine mapped using next generation sequencing technologies. BC-RIL and F2 population derived from the cross of introgression line pau 16057 (syn. T393-4, IC0616573, INGR 15047) with WL711 segregated for a single gene, each for leaf rust and stripe rust resistance. New SSR and STS markers were designed from the IWGSC survey sequence of chromosome 5D to fine map these genes. Lr57-Yr40_CAPS and 5DS-219 were found to be closely linked to the genes, spanning a region of 5.1cM. To further narrow down the region, SNP based markers were designed from flow sorted chromosome 5D sequence of pau 16057 and WL711. SNPs were identified between the two chromosome sequences and validated through KASP technology. Integrating POPSEQ based ordering of wheat contigs information with SNP discovery in pau 16057 and WL711 sequence, the introgressed segment was found to be locating from 0 to 11.94 cM bin. KASP228 and KASP225 are found to be closely linked to Lr76 and Yr70 and can be used in breeding programmes. We have also established that Lr76 and Yr70 are different from previously mapped Lr57/Yr40 genes in the same region on the basis of their location in 11.94 cM and 4.37 cM POPSEQ bin, respectively. In the present investigation, we have used RenSeq which is based upon the knocking down of the major gene and identification of mutations in the NB-LRR encoding genes in all the mutants of the investigated gene. We have identified two NB-LRR encoding contigs in two mutants of Lr76 which needs further validation. In the present investigation, high end sequencing technology like RenSeq and chromosome sorting and sequencing have been used which made it possible to characterize the introgressed alien segment linked to the rust resistance genes.
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