Exploration Of Novel Wheat Powdery Mildew Resistance Genes In Einkorn

Powdery mildew, caused by Blumeria graminis(DC.) E. O. Speer f. sp. tritici (Bgt), isone of the devastating diseases of wheat. Breeding and deploying cultivars carryingresistance genes against powdery mildew is the key measure to control this disease. Tosearch for new powdery mildew resistance genes, eight einkorn accessions and two emmeraccessions were studied for the inheritance of their resistance to powdery mildew. Theresults showed that einkorn accessions 223410, 223418, 223423 and 223426 each carried adominant resistance gene, 223404 and 223414 each had a recessive resistance gene, andeinkorn accessions 223405 and 223409 and emmer accessions 22309 and 223310 eachcarried more than one resistance genes. Allelism tests indicated that the resistance genes in223410, 223418, 223423 and 223426 were likely allelic or tightly linked to each other, aresistance gene in 223409 was also likely allelic or linked to the resistance gene in 223410,the resistance gene in 223404 was inherited independent of that in 223410, and 223309might carry resistance genes allelic or linked to that in 223310.Marker mapping of the resistance gene, Mlm2033, in 223410 and that, Mlm80, in223426 indicated that they were both closely linked to Xgwm344 on the long arm ofchromosome 7A. To establish their genetic relationship with Pml on 7AL, five RFLPmarkers previously reported to co-segregate with Pmla were converted to STS markers,three of which detected polymorphism between the mapping parents and were mappedclose to Mlm2033 or Mlm80. Xmag2185, the locus determined by the STS marker derivedfrom PSR680, one of the RFLP markers, was placed less than 2 cM away from Mlm2033and Mlm80, suggesting that they are allelic or tightly linked to Pmla. In addition, through comparative and EST mapping, more markers linked to these two genes were identified.This research established the basis for map-based cloning of the Pml locus. The markersfor both genes will also facilitate their transfer to wheat.Marker mapping of the resistance gene, mlm404, in 223404 showed that it was flankedby SSR markers loci Xcfd39 and Xgwm126 on chromosome 5AL with a genetic distance of2.8 and 2.0 cM, respectively. To fine mapping the resistance gene, STS markers weredesigned using some RFLP probes and ESTs mapped on the long arm of chromsome 5ALto densify markers on the chromosome region surrounding mlm404, and the STS markermore closely linked to mlm404, MAG1493, was identified. The resistance gene mlm404was tightly linked to TmMlo, the barley Mlo ortholog in T. monococcum, with a geneticdistance 1.0 cM. One amino acid was substituted in the protein encoded by TmMlo of theaccession 223404 compared with that of the susceptible accession 2233389. In addition, thetranscription of TmMlo of 223404 was suppressed. Currently, no known powdery mildewresistance gene was mappd to the locu of mlm404.Genetic analysis showed that a major gene plus several minor genes controlled thepowdery mildew resistance in 223405. A major QTL named as Qpm. nau-5A was identifiedthrough simple interval mapping using 177 F_2:3 families in the intervalXzmf39/Xmag1491～Xmag1493 on chromosome 5AL. This QTL explained 57.8%phenotypic variation, of which the resistance allele originated from the resistant parent223405 and the dominant allele originated from susceptible parent 223389 with a degree of73.4%. Qpm. nau-5A was likely allelic to mlm404 according to its linked molecularmarkers.