High-density Genetic Map Construction And QTL Mapping For Powdery Mildew Resistance In A Doubled Haploid Population From The Yangmai 16/Zhongmai 895 Cross

Powdery mildew,one of the most damaging fungal diseases for wheat production in China,has occurred on an average of over seven million ha during the past five years and was particularly damaging in the Yellow and Huai River Valley,the Middle and Lower Yangtze River Valley.It is important for resistance breeding to search for new genes or quantitative trait loci(QTL)for powdery mildew resistance and promptly incorporate them into breeding materials.The aim of this study was to identify QTL for adult-plant resistance to powdery mildew in a doubled haploid(DH)population including 198 lines derived from a cross between two Chinese leading wheat cultivars Yangmai 16 and Zhongmai 895 using a high-density linkage map based on wheat 660 K SNP array.The main results are summarized as follows:1.High-density genetic map construction.The 198 DH lines from the cross of Yangmai 16/Zhongmai 895 was analysed by wheat 660 K SNP array.For all the 630517 SNPs,151286(24.0%)were polymorphic between the parents.A total of 148179 SNP markers(fall in to 14467 bins)and 12 gene-specific KASP markers were mapped on 21 linkage groups representing all wheat chromosomes,covering 3681.7 cM,with an average marker interval of 0.25 cM.2.Adult-plant maximum disease severities(MDS)evaluation and QTL analysis.The DH lines were phenotyped in multiple field-year trials,including four environments in the 2016–2017 cropping season and two environments in 2017–2018.Composite interval mapping(CIM)detected six stable QTL for adult-plant resistance to powdery mildew,mapped on 2DL,4BS,4DS,5DS,6BL and 7BS,explaining 3.8 to 23.6% of the phenotypic variances across environments.QPmyz.caas-5DS,QPmyz.caas-6BL and QPmyz.caas-7BS,are likely new QTL.3.KASP marker design.One SNP marker closely linked to QPmyz.caas-6BL,the most stable QTL,was successfully converted into a KASP(Kompetitive Allele-Specific PCR)marker(K_AX-94973433)and validated on 103 commercial wheat cultivars.Significantly lower MDS of cultivars with the resistance-associated allele than those with susceptibility-associated allele at QPmyz.caas-6BL in 2017 Beijing indicating partial effectiveness of the marker.The novel QTL for adult-plant resistance to powdery mildew and their closely linked markers identified in the present study should facilitate development of cultivars with improved powdery mildew resistance.