Molecular Identification Of The Powdery Mildew Resistance In Wheat Cultivar Jimai 23 And Marker-assisted Breeding

Common wheat(Triticum aestivum L.)is one of the most important grain crops in China,and its high and stable yield plays an important role on food security.Powdery mildew is a leaf disease caused by Blumeria graminis f.sp.tritici(Bgt),which has devastating impacts on yield.Using host resistance by cultivating resistant wheat varieties is regarded as the most economical,efficient and environmental-friendly measure,especially those derived from vectors with excellent agronomic and yield traits.Jimai23 is an elite wheat cultivar showing high resistance to powdery mildew at adult-plant stage for consecutive years,and also showed broad spectrum resistance to different Bgt isolates.To clarify and better use the powdery mildew resistance in Jimai23,the following studies were conducted:(1)By using different Bgt isolates,genetic analysis indicated that powdery mildew resistance in Jimai23 was mediated by a single dominant gene,tentatively designated Pm JM23,which was inherited the Pm genes on 5DS resistance locus of its parent Jimai22.(2)Using bulked segregant RNA-Seq(BSR-Seq),a series of markers was developed and used to map Pm JM23.Pm JM23 was then located at the Pm2 locus on the short arm of chromosome 5D(5DS).Resistance spectrum analysis demonstrated that Pm JM23 provided a broad resistance spectrum different from that of the documented Pm2 alleles,indicating that Pm JM23 is most likely a new allele of Pm2.(3)In view of these combined agronomic,quality,and resistance findings,Jimai23 is expected to be a valuable resource for wheat disease resistance breeding.To efficiently use Pm JM23 in breeding,the closely linked markers of Pm JM23 were evaluated and confirmed to be applicable for marker-assisted selection(MAS).Using these markers,a series of resistant breeding lines with high resistance and desirable agronomic performance was selected from the crosses involving Pm JM23,resulting in improved powdery mildew resistance of these lines.(4)To analyze the molecular mechanism of Pm,we used the resistant wheat cultivar Jimai 23 to investigate its potential resistance components and profiled its expression in response to powdery mildew infection using bulked segregant RNA-Seq(BSR-Seq).The susceptible wheat cultivar Tainong 18 was crossed with Jimai 23 to produce F1,F2 and F2:3 populations for genetic analysis and BSR-Seq analysis.3,803 differentially expressed genes(DEGs)between parents and bulks were analyzed by GO,COG and KEGG pathway enrichment.The temporal expression patterns of associated genes following Bgt inoculation were further determined by RT-q PCR.Expression of six disease-related genes was investigated during Bgt infection and might serve as valuable genetic resources for the improvement of durable resistance to Bgt.Among them,the transcriptional levels of two genes(Traes CS5D01G018000 encoding an early-responsive to dehydration(ERD)stress family protein and Traes CS5D01G117600 encoding a 70 k Da heat shock protein(HSP70)were rapidly up-regulated indicated that they these two genes in JM23 may be key to its resistance to powdery mildew,while,the other four genes Traes CS5D01G104700,Traes CS5D01G105200,Traes CS5D01G105200 and Traes CS5D01G111400 may be involved in the indirect response of cells after Bgt inoculation.