Molecular Mapping of Leaf and Stripe Rust Resistance Genes In T. Monococcum and Their Transfer to Hexaploid Wheat

Abstract

Wheat as a crop has benefited immensely from genetic improvement programmes but wheat production is still being challenged constantly by several diseases; among them, rusts are the most prominent. Leaf rust is the most widely distributed desease of wheat despite the fact that major emphasis has been made to develop rust resistant varieties. Deployment of major genes has often turned out to be non-durable and in India most of the genes identified from cultivated germplasm are not effective against the prevalent pathotypes of leaf rust. A spring type Triticum monococcum (acc. 14087) has maintained a high level of resistance to Indian isolates of leaf and stripe rust. Genetic studies using a set of 125 recombinant inbred lines (RILs), developed from a cross T. monococcum (acc. 14087)/T. boeoticum (acc. 5088) revealed that both T. monococcum and T. boeoticum have one APR gene that confers resistance to stripe rust and one seedling and one adult plant resistance gene for leaf rust. A genome linkage map with more than 150 markers, including RFLPs, SSRs and bin mapped ESTs, has been generated using the RIL population. QTL analysis revealed the presence of leaf and stripe rust resistance genes on chromosome 2A. Attempts were made to transfer both leaf and stripe rust resistance genes from T. monococcum to hexaploid wheat using T. durum cv N59 as a bridging species. Screening of F1 and backcross generations revealed that B genome of T. durum suppresses resistance of T. monococcum. With subsequent backcrosses one seedling and one APR gene for leaf rust and one APR gene for stripe rust resistance have been transferred from T. monococcum to bread wheat cv. WL711 and one APR gene for leaf rust has been transferred in PBW343 background. Chromosome number of the resistant plants varied from 39–kern0.5pt41. The leaf and stripe rust resistant plants are being analyzed with SSR markers that were found to be associated with leaf and stripe rust resistance genes based on QTL mapping in the RIL population