Physical Mapping Of Powdery Mildew Resistance Genes MlIW170?Pm26?MlWE74 And PmWE35 Originated From Triticum Dicoccoides

Powdery mildew and stripe rust are the severest fungal wheat diseases worldwide,which can reduce wheat yield and quality severely.Discovering novel resistance genes and identifying the linked molecular markers will contribute to pyramiding multiple resistance genes and developing new wheat cultivars with durable and broad-spectrum disease resistance.Wild emmer,the immediate progenitor of both cultivated tetraploid and hexaploid wheats,contains abundant resistance genetic resources.Powdery mildew resistance gene MIIW170,Pm26,MIWE74 and PmWE35 were originated from wild emmer and located on chromosome 2B.In this study,highly density genetic linkage maps and physical maps of MlIW170,Pm26,MlWE74 and PmWE35 were constructed using the reference genome sequences of T.aestivum cv.Chinese Spring and T.dicoccoides cv.Zavitan.PmWE35 was proved to be a new powdery mildew resistance gene and tightly linked with yellow rust resistance gene Yr5 on 2BL.The main results are as following:1.Polymorphic markers were developed to construct a highly density genetic linkage map of MlIW170 using a large mapping population.MlIW170 was delimited to a 0.06 cM genetic interval between markers WGGBH1388 and WGGBY776,which contained 5 and 6 putative genes in the candidate regions of T.aestivum Chinese Spring and T.dicoccoides Zavitan,respectively.RNA-Seq analysis revealed that 3 transcripted NB-ARC-LRR genes may serve as candidates of MIIW170 for further functional characterization.2.Polymorphic markers were developed for fine mapping Pm26 with 2664 F2 plants.Pm26 was narrowed down to a 0.208 cM genetic interval between markers WGGBD864 and WGGBD661 that corresponded to a 81 Kb physical region containing 3 putative genes in Chinese Spring.Sequence comparisons indicated that a 73.6 Kb deletion was presented in Pm26-40 and Zavitan.3.A new mapping population was constructed for fine mapping powdery mildew resistance gene MlWE74 using new developing polymorphic markers.Markers WGGBD412 and WGGBD425 could delimit MlWE74 into a 0.12 cM genomic region,corresponding to 13 Kb physical region containing 2 phosphoglycerate mutase gene in T.aestivum Chinese Spring and T.dicoccoides Zavitan,respectively.4.Powdery mildew resistance genes MIIW170,Pm26 and MIWE74,originated from wild emmer,were found to be tightly linked on chromosome 2BS.Different reactions of IW170,Pm26-40 and WE74 to 36 isolates of B.graminis f.sp.tritici were observed.5.Polymorphic markers were developed to construct a fine genetic linkage map of PmWE35 and Yr5.PmWE35 was found to be tightly linked in repulsion with Yr5 in a 0.06 cM genetic region,corresponding to 5.69 cM physical distance containing 40 and 39 putative genes in T.aestivum Chinese Spring and T.dicoccoides Zavitan,respectively.Compared with other powdery mildew resistance genes mapped on chromosome 2BL,Pm WE35 was proved to be a new powdery mildew resistance gene.