Identification Of Wheat Leaf Rust Resistance Genes In 108 Wheat Cultivars And QTL Analysis For Adult Plant Resistance Gene To Stripe Rust In Wheat Landrace Xu’ai

Wheat rust is the most important wheat diseases which can seriously endanger wheat production in China.Since the 1950 s,there have been many large scale wheat leaf rust and stripe rust epidemics,which have caused serious losses to the Chinese wheat in yield and quality.Therefore,the most economical and effective way to control wheat rust is breeding disease resistant varieties.The content of this study can be divided into two parts: The first part is analysis of wheat leaf rust resistance genes in 108 important wheat cultivars;the second part is QTL analysis for adult plant resistance genes to stripe rust in RIL population from the cross of Xu’ai/Zhengzhou 5389.1.A total of 108 wheat cultivars from Beijing and Shandong province and a set of 36 differential lines,mostly near-isogenic lines in the background of Thatcher with known leaf rust resistance genes,were tested for response to 20 P.triticina pathotypes at the seedling stage in the greenhouse.These genotypes were also planted in the field to test their slow rusting resistance using mixed races in Baoding,Hebei province and Zhoukou,Henan province during the 2014-2015 and 2015-2016 cropping seasons.Ten leaf rust resistance genes,viz.Lr1,Lr9,Lr10,Lr19,Lr20,Lr24,Lr26,Lr34,Lr37 and Lr46 were confirmed in the 108 commercial wheat cultivars using molecular markers.Combined,the results from gene postulation and marker detection showed that one or more of the genes Lr1,Lr3,Lr10,Lr14 a,Lr14b,Lr26,Lr36,Lr39,Lr34 and Lr46,were present in 51 cultivars,and known resistance gene was not present in the remaining 57 cultivars.The resistance gene Lr26 was present in 42 cultivars,and nine cultivars contained Lr1.Lr46 was present in 10 cultivars based on the presence of the closely linked marker csLV46G22.Seven genotypes were identified as possibly carrying gene Lr39.Lr3 and Lr10 were found in six and four genotypes,respectively.Genes Lr14 b and Lr34 were each present in three cultivars,while evidence for the presence of Lr14 a and Lr36 was obtained in single genotypes.Finally,12 cultivars showed slow rusting resistance at two locations in two crop seasons.Identifying leaf rust resistance genes in Chinese wheat cultivars will be helpful for gene deployment to controll leaf rust.2.Another part is the quantitative trait loci analysis of adult plant resistance to stripe rust for Xu’ai/Zhengzhou 5389 wheat RILs.The wheat landrace showed high resistance to stripe rust at adult stage,suggesting that Xu’ai/Zhengzhou 5389 might contain adult resistance genes.To identify the adult plant resistance genes,the QTL mapping of 158 RILs from the cross Xu’ai/Zhengzhou 5389 was sown in Baoding,Hebei province and Mianyang,Sichuan province field nursery sites during the 2015-2016 and 2016-2017 cropping reasons.The markers(SSR and SNP)were used to screen markers among parents,RIL populations for QTL analysis.Field resistance identification data and molecular marker data were used in QTL analysis for resistance to stripe rust by QTL Ici Mapping 4.0 and Map Manager QTXb20.In this study,3 QTLs were identified located on 1BL,4B and 6A,respectively.The QTL located on 1BL chromosome provided by Yr29/Lr46/Pm39 was expressed in one environment and explained at 7.8% phenotypic variance.The QTL on 4B chromosome was detected in four environments explained 24.5-35.6% phenotypic variance;Another QTL located on 6A chromosome was detected in two environments,explaining 23.5% and 11.4% phenotypic variances respectively.It is important to map adult plant resistance genes for breeding wheat cultivars with durable resistance to wheat rust disease.