利用BC2F2高代回交群体定位水稻籽粒大小和形状QTL

以我国优良籼稻恢复系蜀恢527为轮回亲本, 以来自菲律宾的Milagrosa为供体亲本, 培育了样本容量为199株的BC₂F₂高代回交群体。选取85个均匀分布在12条染色体上的多态性SSR标记进行基因型分析, 同时对粒长、粒宽、长宽比和千粒重4种性状进行了表型鉴定。采用性状－标记间的单向和双向方差分析对上述性状进行了QTL定位。单向方差分析(P<0.01)共检测到了10个控制粒长、粒宽、长宽比和千粒重的QTL, 其中有3个具有多效性。由于粒长和长宽比的高度相关性, 控制长宽比的2个QTL均能在粒长QTL中检测到。位于第3染色体着丝粒区域的qgl3b是一个控制粒长、长宽比和千粒重的主效QTL, 它可以分别解释粒长、长宽比和千粒重表型变异的29.37%、26.15%和17.15%。该QTL对于粒长、长宽比和千粒重均表现较大的加性效应(来自蜀恢527的等位基因为增效)和负向超显性。位于第8染色体的qgw8位点是一个控制粒宽的主效QTL, 同时也是控制千粒重的微效QTL, 能解释粒宽表型变异的21.47%和千粒重表型变异的5.16%。该QTL对粒宽和千粒重均具有较大的加性效应(来自蜀恢527的等位基因为增效)和正向部分显性。双向方差分析(P<0.005)共检测到61对显著的上位性互作, 涉及54个QTL, 其中23个是能同时影响2~4个性状的多效位点, 且有8个位点与单向方差分析检测到的相同。控制长宽比的13对上位性互作位点中, 与控制粒长的上位性互作位点完全相同的有8对。以上结果为进一步开展水稻籽粒大小和形状有利基因的精细定位、克隆和分子设计育种奠定了基础。

QTL Detection of Grain Size and Shape with BC2F2 Advanced Backcross Population of Rice (Oryza sativa L.)

The traditional mapping population with complicated genetic backbround is usually derived from a cross between two parents with a lot of unfavorable agronomic traits. The identified QTLs by traditional mapping can not be applied in genetic improvement of crops due to complicated interactions between QTLs and genetic background. The advanced backcross method for QTL mapping with elite variety as recurrent parent could partially eliminate the background effects and integrate QTL mapping with genetic breeding. In present study, using Shuhui 527, an elite indica restorer in China as recurrent parent and Milagrosa from Philippines as donor, the BC₂F₂ advanced backcross population with 199 individuals was developed. A total of 85 polymorphic SSR markers evenly distributed on 12 chromosomes were applied to genotype the mapping population. The grain length, grain width, ratio of grain length to width and thousand grain weight of the parents and the BC₂F₂ population were evaluated after har-vesting. The QTL identification of the above traits was conducted by one-way ANOVA (for single QTL) and two-way ANOVA (for digenic epistatic interaction loci). Among ten QTLs for grain length, grain width, ratio of grain length to width and thousand grain weight detected by one-way ANOVA (P<0.01), there were three pleiotropic QTLs. QTLs for ratio of grain length to width could be identified in QTLs for grain length due to highly close relationship between them. The results in present study indicated that qgl3b on chromosome 3 was a major QTL controlling grain length, ratio of grain length to width and thousand grain weight, which explained 29.37%, 26.15%, and 17.15% of phenotypic variation of the three traits and showed large additive effects (posi-tive allele from Shuhui 527) and negative overdominant effects, qgw8 was also a major QTL controlling grain width with 21.47% contribution to phenotypic variation and a minor QTL controlling thousand grain weight with 5.16% contribution to phenotypic variation. It had large additive effects (positive allele from Shuhui 527) and positive partial dominant effects in both traits. Two-way ANOVA (P<0.005) showed 61 pairs of digenic epistatic interactions involved in 54 QTLs among which 23 loci had pleiotropism affecting two to four traits and eight loci were the same as those detected by one-way ANOVA. It was observed that eight of thirteen pairs of digenic epistatic interactions related to ratio of grain length to width could be found in grain length. The results above will lay a good foundation in fine mapping, cloning and designed molecular breeding of favorable genes related to rice grain size and shape.