基于55K SNP芯片的普通小麦穗长非条件和条件QTL分析

Unconditional and Conditional QTL Analysis of Wheat Spike Length in Common Wheat Based on 55K SNP Array

【目的】进一步挖掘小麦穗长具有利用价值的数量遗传位点(QTL),同时深入探究穗长与其他重要农艺性状之间的遗传关系,为精细定位和分子辅助选择育种奠定基础。【方法】以20828为母本、SY95-71为父本,构建126份F7代重组自交系群体。将亲本及其重组自交系分别于2016—2017年和2017—2018年生长季种植在中国四川省成都市温江区试验基地、中国四川省崇州市试验基地、中国四川省雅安市试验基地以及孟加拉国库尔纳市试验田,调查7个不同环境下的穗长表型。利用基于小麦55K SNP芯片构建的遗传连锁图谱进行非条件QTL的定位,并分析其效应。分别以株高、穗茎长、每穗小穗数和千粒重为条件,对定位到的主效QTL进行条件QTL分析,分析穗长与它们的遗传关系。【结果】通过非条件QTL定位到13个穗长QTL,分别位于1A、1D、2B、2D、4B、6D和7A染色体,LOD值为2.79—6.19,贡献率为5.35%—12.77%。其中,定位到3个稳定遗传的主效QTL:QSl-sau-2SY-2B、QSl-sau-2SY-2D.5和QSl-sau-2SY-4B,贡献率分别为6.54%—11.72%、10.16%—12.57%和5.35%—10.92%。这三个主效QTL在多环境分析中也可以检测到。进一步聚合分析表明,聚合QSl-sau-2SY-2B、QSl-sau-2SY-2D.5和QSl-sau-2SY-4B增效位点的株系穗长表型显著长于聚合任意2个主效QTL或仅含单个主效QTL增效位点的株系。同时,发现QSl-sau-2SY-2B对于株高、穗茎长、每穗小穗数和千粒重均没有显著影响,QSl-sau-2SY-2D.5对于千粒重有显著影响,达到3.98%,而对于株高、穗茎长和每穗小穗数没有显著影响,QSl-sau-2SY-4B对于株高和穗茎长有极显著影响,分别达到-12.28%和-22.26%,而对于每穗小穗数和千粒重没有显著影响。条件QTL分析结果表明,在QTL水平上,QSl-sau-2SY-2B与株高和穗茎长无关,但受到每穗小穗数和千粒重的影响,QSl-sau-2SY-2D.5与穗茎长、每穗小穗数和千粒重无关,但受到株高的影响,QSl-sau-2SY-4B与穗茎长和千粒重无关,但受到株高和每穗小穗数的影响。【结论】定位到3个控制穗长且稳定遗传的主效QTL——QSl-sau-2SY-2B、QSl-sau-2SY-2D.5和QSl-sau-2SY-4B。其中,QSl-sau-2SY-2B可能为新的QTL,独立于株高和穗茎长遗传。

【Objective】This study is to excavate spike length(SL)-related quantitative trait loci(QTL)with potential breeding value,explore the genetic relationship between SL and other important agronomic traits in wheat,and aim at laying a foundation for fine mapping and molecular-assisted selection breeding.【Method】A total of 126 F7 recombinant inbred lines(RIL)constructed by crossing 20828 and SY95-71 were used in this study.The RIL population including their parents were planted in seven different environments for phenotypic evaluation:Wenjiang,Chongzhou,Ya’an of Sichuan Province in China,and Khulna in Bangladesh during 2016-2017 and 2017-2018 growing seasons.Unconditional QTL mapping was performed using a genetic linkage map constructed using the wheat 55K SNP array,and QTLs’effects were further analyzed.Conditional QTL analysis was performed to analyze the relationship between SL and other agronomic traits including plant height(PH),spike extension length(SEL),spikelet number per spike(SNS)and thousand-kernel weight(TKW).【Result】Thirteen QTLs controlling SL were identified using unconditional QTL mapping,and they were located on chromosomes 1A,1D,2B,2D,4B,6D,and 7A.The LOD values ranged from 2.79 to 6.19,and the phenotypic variation rate ranged from 5.35%to 12.77%.Three stable and major QTLs(QSl-sau-2SY-2B,QSl-sau-2SY-2D.5 and QSl-sau-2SY-4B)were identified,and they explained 6.54%to 11.72%,10.16%to 12.57%,and 5.35%to 10.92%of phenotypic variation rate,respectively.Furthermore,these three major QTLs could be also detected in multi-environment analysis.Moreover,aggregation analysis suggested that the SL of lines polymerizing the positive allels at these three major QTLs was significantly longer than that of those with any two ones or those carrying only one.Meanwhile,it was found that QSl-sau-2SY-2B had no significant effect on PH,SEL,SNS and TKW.QSl-sau-2SY-2D.5 had a significant effect on improving TKW(3.98%),but no significant effect on PH,SEL and SNS.QSl-sau-2SY-4B had a significant effect on decreasing PH(-12.28%)and SEL(-22.26%),but no significant effect on SNS and TKW.The conditional QTL analysis showed that QSl-sau-2SY-2B was independent of PH and SEL,whereas,affected by SNS and TKW.QSl-sau-2SY-2D.5 was independent of SEL,SNS and TKW,but affected by PH.QSl-sau-2SY-4B was independent of SEL and TKW,but affected by PH and SNS.【Conclusion】In this study,three stable and major QTLs were identified for SL:QSl-sau-2SY-2B,QSl-sau-2SY-2D.5,and QSl-sau-2SY-4B,among which QSl-sau-2SY-2B may be a novel QTL independent of PH and SEL.