Synthetic hexaploid wheats(SHWs),obtained by crossing tetraploid wheats(AABB) with Aegilops tauschii Coss(DD),containing genetic variability in bread wheats(BWs,Triticum aestivum),and being novel sources of useful traits for broadening the diversity in breeding germplasm of BW,now have been widely used for genetic improvement of BWs.A total of 117 synthetic backcross-derived lines(SBLs) in which four commercial cultivars Chuanmai 38,Chuanmai 42,Chuanmai 43 and Chuanmai 47 were widely grown with their super high yield and excellent resistance to rust disease and good quality in Chengdu plain in China were from the crosses of four BC2F2:6 CIMMYT SHWs and 5 commercial cultivars of BW were used to access the extent of genetic diversity by a set of 37 genomic-derived microsatellite markers(SSRs) representing at least one marker from each chromosome of the genomes A,B and D.That the 37 SSR markers amplified 256 allelic fragments ranged widely from 1 to 14 with an average allelic variant number of 6.92 per locus across all genotypes showed SSR marker represents a higher genetic variation in the SBLs.In the genomes A,B and D,Polymorphic information content(PIC) in genome D was the lowest with 0.427 6,next was genome B with 0.534 6 and the highest was 0.614 5 in genome A(A>B>D).The results of Simpson's index(SI) comparison also showed the same trends that genome A was the highest with 1.187 4,next was genome B with 1.081 and genome D was the lowest with 0.804 6(A>B>D).The average genetic similarity coefficient of 37 SSR marker loci in genomes A,B and D was 0.472 1,0.379 7 in genome A,0.462 7 in genome B and 0.581 5 in genome D,respectively(A>B>D).All of which showed that the level of the genetic diversity of the synthetic backcross-derived lines from the synthetic hexaploid wheats and bread wheats was higher.Based on percentage difference,a cluster dendrogram analysis to reveal associations between lines,families or types by the unweighted paired group method with arithmetic averages(UPGMA) was presented calculated by the SSR-derived data and showed that genetic similarity coefficients were lower between the genotypes in genomes A,B and D.All of these indicated that SHWs and SBLs are a valuable resource for broadening the genetic base of elite wheat breeding germplasm.Fingerprinting of SBLs and their corresponding SHW and BW parents,and testing for selective advantage of SHWs alleles promises to be a useful method for detecting chromosomal regions and functional genes of interest for bread wheat improvement.%通过四倍体二粒小麦和节节麦杂交而获得的人工合成六倍体小麦,含有丰富的普通小麦品种改良有益基因,作为拓宽普通栽培小麦性状和新品种改良的新的种质资源已广泛应用于普通小麦的遗传改良实践中.利用分布于小麦A、B、D基因组21条染色体、28个不同染色体臂上的37对微卫星引物,对人工合成六倍体小麦与四川成都平原普通栽培小麦主栽品种杂交、回交经多代选择而形成的117份人工合成六倍体小麦衍生后代高代群体系(其中川麦38、川麦42、川麦43和川麦47为审定品种)进行了DNA分子水平上的分析,共检测到256个等位基因变异,平均每个SSR标记位点检测到6.92个等位变异基因.每个SSR位点等位基因变异数在1～14个,变异幅度较大,表明SSR分子标记在人工合成六倍体小麦中表现出高水平的遗传变异.A,B,D基因组中,D基因组表现出的多态性信息含量最低,为0.427 6,B基因组次之,为0.534 6,A基因组最高,达到 0.614 5(A>B>D).辛普森指数比较的结果也反映出相同的变化趋势,A基因组最高,为1.187 4,B基因组次之,为1.081,D基因组最小,为0.804 6(A>B>D).综合多态性信息含量和辛普森指数的估值,表明这一批人工合成六倍体小麦后代衍生高代群体接受的遗传基因既来自人工合成六倍体小麦,又来自普通栽培小麦,显示杂合度类型丰富,具有较高的遗传差异.根据获得的等位基因变异片断的分布情况进行UPGMA聚类,发现A,B,D基因组基因型间的遗传相似系数较低, A,B,D三基因组37个SSR标记位点所得平均遗传相似系数为0.472 1,A基因组平均遗传相似系数为0.379 7,B基因组平均遗传相似系数为0.462 7,D基因组上平均遗传相似系数为0.581 5,反映出人工合成六倍体小麦后代衍生群体材料的遗传多样性处于较高水平.本研究结果证明利用人工合成六倍体小麦所具有的普通小麦野生近缘种中的基因库改良现代小麦,丰富其遗传基础,减少其生物和非生物胁迫的脆弱性,是一条行之有效的途径.
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