Genetic Analysis and Molecular Mapping of Durable Yellow and Leaf Rust Resistance In Hexaploid Wheat Line “Quaiu 3”.

ABSTRACT

Though scientists have been investing their efforts to identify rust resistance genes for the last fifty years, their successes have been transient due to continuous emergence of new pathogen races in short spans of time. Achieving durable resistance to stripe (YR, caused by Puccinia striiformis Westend) and leaf rust (LR, caused by Puccinia recondita f.sp. tritici) in wheat (Triticum aestivum Desf.) has been a major objective of breeding programs for long. The durability of resistance to YR and LR is considered to be associated with non-hypersensitive adult-plant resistance (APR) genes which are inherited quantitatively. Several phenotypic screenings have shown that durable resistance provided by ‘Quaiu 3’ seems to be unique and promising, which, after characterizing in molecular level for both rust types, can be combined with other sources to achieve higher level of durable resistance in the future. The objectives of this study are to 1) analyze the inheritance pattern of durable resistance in the spring wheat line Quaiu 3, and 2) map the resistant QTLs/genes using molecular markers. One hundred and ninety seven F_4:5 recombinant inbred lines (RILs) derived from Quaiu 3 and ‘Avocet-YrA’ were evaluated for adult plant resistance to YR and LR in artificially inoculated field in Mexico during 2009, 2010 and 2011. The disease severity and infection type data showed that there are 2-3 adult plant resistance genes associated with LR and YR resistance. Preliminary results from single marker based QTL analysis using DArT (Diversity Arrays Technology) markers have shown that there are three major QTLs (on chromosome arms 1A, 1B and 1D) associated with APR to leaf rust. Similarly, four QTLs (on chromosome arms 1B, 2B, 2D, 3B) have been found to be associated with APR to stripe rust. After further saturation of linkage map with SSR markers, composite interval mapping will be carried out and characteristics of consistent QTLs will be reported in detail.