QTL Mapping For Adult-plant Resistance To Leaf Rust In Chinese Wheat Cultivar Mianyang351-15

Wheat leaf rust, caused by Puccinia triticina, is one of the important diseases thatdamage wheat production in China. Continuing screening, breeding, and planting theresistant cultivars is the most economical, safe and effective method to control wheat leafrust. It is necessary to study leaf rust resistance genes in wheat cultivars and geneticresources for breeding wheat cultivars with durable resistance to leaf rust and resistancegene deployment. The seedling race specific genes can easily lose resistance when virulentraces emerge or increase, but most of adult plant resistance are quantitative trait controlledby multiple genes with durable resistance, and most adult plant resistance genes conferresistance to a variety of diseases simultaneously. At present some seedling race specificgenes were found and located in Chinese wheat lines, but few researches about adult plantresistance QTLs were reported in Chinese wheat lines. Therefore mapping adult plantresistance QTLs in Chinese wheat lines is very important for breeding with durableresistance to leaf rust.In the study, Mianyang351-15, Zhengzhou5389and their203F2:3lines were used tomap adult plant resistance QTL in Mianyang351-15. Former reports conformed thatMianyang351-15carried seedling resistance gene Lr1, which had lost resistance to most ofP. triticina pathotypes, but Mianyang351-15showed high resistance to mixture of the P.triticina pathotypes at adult plant stage in the field, indicating that Mianyang351-15mightcontain adult plant resistance genes. To map the adult plant resistance QTLs,203F2:3lineswere phenotyped for their leaf rust severities in the field during2010to2012crop seasons,and1315SSR markers and1CAPS marker were screened between parents and smallresistant and susceptible groups. Phenotypic and genotypic data were combined to mapadult plant resistance QTLs in Mianyang351-15using software QTL MapmanagerQTXb20and IciMapping3.1. The results showed that adult plant resistance geneLr46and Lr68were present in Mianyang351-15, and4QTLs on chromosome1BL,2AS,7BL were detected in Mianyang351-15, and three QTLs were identified in both of the twoseasons. The four QTLs were named QLr.hbau-1BL、QLr.hbau-2AS、QLr.hbau-7BL.1andQLr.hbau-7BL.2, and their maker intervals were Xwmc719-XcsLVg22, Xwmc667-Xwmc382,Xwmc719-csLV46g22and Xbarc182-Xwmc273respectively. In2011, three QTLs explained18.5%,18.4%and5.2%of the phenotypic variation, respectively. Four QTLswere detected in2012, and explained4.3%,38.8%,21.2%and28.6%of the phenotypicvariation respectively. Changes of the effects of the two QTLs near the two genes Lr46andLr68in the two years indicated the interaction between genes and environment wassignificant. QTL on2AS has not been reported yet at present, indicating the QTL may be anew adult plant resistance gene. Fine mapping of the new QTL should be done in next stepto clone the gene.