| Powdery mildew(Blumeria graminis f.sp.tritici)is one of the main diseases in wheat,and it seriously threatens the safety of wheat production.Practices illustrate that breeding resistant cultivars is the most effective,economic and environmental-friendly method,which is the key factor to look for new powdery mildew resistant genes,and new cultivars with broad spectrum and durable resistance will be developed by pyramiding the genes using marker-assisted selection.The waxy on the spike is the outer layer that contacts directly to the outside,which can protect wheat from UV and pests,moreover,some researchers suggested that the waxy was important to drought resistance in wheat,and it significantly influence to the growth and development of wheat.Wild emmers consist of abundant disease-resistant genes and ecological variations,furthermore,they could cross with common wheat easily and have huge potential to increase disease-resistance and adaptability of common wheat.In this study,we used an introgression line from wild emmers hybridized with common wheat as the accession and designed makers linked closely with MLIW30 controlling powdery mildew and Iw3 restraining the production of the waxy respectively,combining wheat Illumina 90 k iSelect SNP chip and comparative genomics,then their genetic linkage map were constructed.The detail is following:1.We designed 7 markers linked closely with MLIW30 by wheat 90 k SNP chip,meanwhile,polymorphic SNPs were analyzed with brachypodium distachyon,rice and sorghum collinearitily,and the segment of MLIW30 corresponds to chromosome 1 of brachypodium distachyon,chromosome 6 of rice and chromosome 10 of sorghum.We mapped the MLIW30 in long arm of 4A chromosome using 9 polymorphism markers,and the nearest makers are XB1g2020.2 and XB1g2000.2,0.1 cM to the gene,respectively.Besides,XB1g2000.2 and XB1g060.2 both link to MLIW30 were detected specifically in 36 wheat accessions in 9 nations,then transforming the resistant gene MLIW30 using these two makers into powdery mildew-susceptible varieties Liaochun 10,Xuezao,87-1,Morocco,as a result,the disease-resistance of those susceptible varieties has been enhanced.2.We designed 8 polymorphic makers by assembled genome sequence of Chinese Spring.7 markers was mapping to Scaffold 16041 and the sequence of Scaffold 16041 was developed 5 polymorphic markers linked with MLIW30.Finally,MLIW30 was located 491kb genomic region between XG223 and XG270.There are 16 genes in the segment by gene prediction.3.According to BSR-seq,58,199 polymorphic SNPs are found between resistant pool and susceptible pool.Association analyzing located the gene in the segment 207,429,679-215,805,806 in chromosome 4A,the total length is 8.38 Mb,including 213 genes.Sequences of 43 genes have polymorphic SNPs between resistant pool and susceptible pool.3 of 43 genes mapping to candidate gene region by sequence comparing and 2 genes with non-sense mutation are genes number 8 and 9,respectively.4.Introgression lines 1A171 and 1A520 from wild emmers contain Iw3 restraining the production of the waxy in the spike,and they hybrid with 87-1.Liaochun 10 respectively and their F2 segregating population are 562 and 494.The distance between marker Xgpw363 and Iw3 is 4.3 cM and 0.9 cM,respectively.Comparative genomic analysis indicate that the target segment were corresponds to chromosome 2 of brachypodium distachyon,chromosome 5 of rice and chromosome 9 of sorghum.Aligning EST sequence in wheat to the gene sequence of brachypodium distachyon and rice,17 EST-STS makers linked with Iw3 are developed,and located it 5 cM and 1.8 cM genetic interval between markers XB2g4004.1 and X05g1016.1,respectively. |
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