Identification Of Leaf Rust Resistance Genes In 66 Wheat Varieties And QTL Mapping For Adult-Plant Resistance To Leaf Rust In Kenya Kudu

Wheat leaf rust is one of the most serious diseases of wheat crops.The disease is caused by wheat leaf rust(Puccinia recondite f.sp.Tritici,Pt),which infects wheat leaf parts and seriously affects wheat photosynthesis,thus causing yield reduction.Practice has proved that the cultivation and utilization of wheat leaf rust resistant varieties are the most economical and effective control measures to control the disease.The discovery and location of new leaf rust resistance(Lr)genes is an important prerequisite for the cultivation of resistant varieties In this study,the resistance of different wheat varieties to leaf rust was studied through two parts of experimental works.The specific work and results are as follows1)Sixty-six wheat varieties from different countries of the world were used to identify Lr genes using gene postulation and molecular marker detection methods.At seedling stage.17 Pt races with different level of virulence were used to inoculate all the wheat varieties and 36 differential lines containing a single known Lr gene.Gene postulation in the varieties was carried out by comparing the infection types of 36 differential lines with that of the tested wheat varieties.At the same time,12 molecular markers closely linked to known Lr grenes were used to detect the DNA of tested varieties to verify the results of gene postulation All the 66 tested varieties were also investigated for leaf rust severity at the field in Zhoukou.Henan province(in 2016/2017)and Baoding,Hebei province(in 2017/2018)fields.The Statistical Analysis System(SAS)was used to analyze the survey data to screen varieties with slow-rusting resistanceThe results showed that among the 66 tested varieties,12 varieties contained Lr1.eight varieties contained Lr26,two varieties contained each Lr20,Lr10 and Lr17,and one variety contained Lr36.Through molecular marker detection of APR genes,14 varieties contained Lr34,three varieties contained Lr37,and five varieties contained Lr46.According to the field investigation results,17 varieties had slow-rusting resistance.These varieties with the corelated known Lr genes and slow-rusting resistance could enrich the existing wheat germplasm resources in China,which is conducive to the research of disease resistance breeding,and at the same time provide genetic basis for the breeding of durable leaf rust resistance.2)Kenya Kudu wheat variety from Kenya showed good adult plant resistance to leaf rust in previous studies.It is speculated that it may contain APR genes.Therefore,QTL analysis and mapping for leaf rust resistance at adult stage were carried out on the F2:3 population of Kenya Kudu and Zhengzhou 5389.One hundred and ninety-five F2:3 lines were planted in Baoding,Hebei province and Zhoukou,Henan province in the 2017/2018 and 201 8/2019 cropping seasons.Mixed Pt races of virulent leaf rust were used to inoculate all the lines in the fields,and the final disease severity was investigated as phenotypic data At the same time,the DNA of five typical resistant lines and five typical susceptible lines,which were selected as the small group,was extracted for 660K SNP detection.SSR markers were screened by using the DNA of the parents and the small groups according to the SNP results.The obtained markers with polymorphism and exchange rate below 30%were further used for detecting all the F2:3 population.QTL analysis and mapping of the phenotypic and genotypic data were performed using Map Manager QTXb 20 and QTL IciMapping 4.1 softwares.In the present experiment,a total of three QTLs were detected in the population.Two QTLs were located on chromosome 5B,temporarily named QLrhbau-5B.1 and QLr.hbau-5b.2.Among them,QLrhbau-5B.1 was detected in four environments explains by 8.3 to 1 0.5%of the phenotypic variance,and was located closely to the known Lr gene,Lr52.But QLr.hbau-5B.1 is a minor QTL,so it may not be Lr52.QLr.hbau-5B.2 was detected in two environments,explaining 6.9 to 8.6%of the phenotypic variance and might be the same APR QTL as that on chromosome 5B found before.One QTL was located on chromosome 2B,temporarily named QLr.hbau-2B.The QTL was detected in four environments and explaining 7.2 to 10.6%of the phenotypic variance.All the QTLs detected in this experiment were minor effective APR QTL,which could provide theoretical support for the cultivation of durable rust resistance wheat varieties in China.