水稻回交群体剑叶性状综合评价及QTL定位

【目的】通过对水稻剑叶性状的综合评价,明确剑叶相关性状间及与6个农艺性状的关系。检测剑叶相关性状的QTL,为优良株型品种选育,剑叶性状基因的精细定位和克隆奠定基础。【方法】以日本优质粳稻品种越光和葡萄牙粳稻地方种Bertone构建的回交群体两个世代为实验材料,利用BC₃F₁群体基因型构建遗传连锁图谱;测定亲本和BC₃F₂群体各株系剑叶SPAD、剑叶长、剑叶宽,计算剑叶长宽比、剑叶面积;利用隶属函数和标准差系数赋予权重法获得剑叶性状综合评价值(D值),分析其与6个农艺性状间的关系。分别利用单标记分析(SPA)和区间作图(IM)检测水稻剑叶相关性状QTL。【结果】在抽穗灌浆期,两亲本剑叶SPAD值呈现先升高后降低的动态变化。BC₃F₂群体的5个剑叶相关性状变异丰富,总体表现趋向轮回亲本越光。4个剑叶形态性状间相关性均达到极显著水平,与剑叶SPAD的相关性不显著。主成分和逐步线性回归分析表明剑叶宽、剑叶SPAD、剑叶长、剑叶面积是影响剑叶综合评价值(D值)的主要因子。高D值株系的株高、穗长、茎基粗和单株产量均极显著高于低D值株系,两者的分蘖数和有效穗数差异不显著。共检测到18个控制剑叶性状的QTL,分布在水稻第1、4、7和8染色体上,贡献率分布范围为4.00%~28.00%(SPA)和3.41%~27.00%(IM),除qFLSPAD1之外的17个QTL增效基因均来自Bertone。在第8染色体上的RM22720-RM404区间发现1个QTL簇,含6个主效QTL,分别为qFLL8.1、qFLL8.2、qFLA8.1、qFLA8.2、qD8.1和qD8.2。【结论】获得了剑叶宽、剑叶SPAD、剑叶长和剑叶面积4个评价剑叶性状的关键指标;明确了剑叶性状与单株产量之间的正相关关系;检测到18个剑叶相关性状QTL,位于第8染色体RM22720-RM404区间的QTL簇,是影响剑叶性状的1个重要染色体区域。

Comprehensive Evaluation and QTL Analysis for Flag Leaf Traits Using a Backcross Population in Rice

【Objective】In order to clarify the correlations between flag leaf-related traits and their relationships with six agronomic traits, a comprehensive evaluation of flag leaf traits was made. The identification of QTLs associated with flag leaf traits will lay a foundation for fine mapping and cloning of the functional genes underlying rice flag leaf-related traits, which is helpful to breed elite cultivars with excellent flag leaf traits. 【Method】A backcross population with two generations derived from an elite japonica rice cultivar Koshihikari (recipient) and a Portuguese rice landrace Bertone (donor) was used as plant materials. The genetic linkage maps were constructed by using SSR markers with the BC₃F₁ population. Several parameters including flag leaf SPAD, flag leaf length, flag leaf width, length to width ratio of flag leaf as well as flag leaf area were measured in the parental varieties and BC₃F₂ population. In order to analyze the relationship between D value and the six agronomic traits, membership functions and the index weight method were used to comprehensively evaluate the flag leaf traits of these 260 BC₃F₂ lines. Single-point analysis (SPA) and interval mapping (IM) were used to identify QTLs for traits related to flag leaf in rice.【Result】After the flag leaf was fully expanded, the flag leaf SPAD values of the two parents showed a dynamic change, increasing at first and reduced subsequently. The five flag leaf-related traits of the BC₃F₂ population exhibited diverse phenotypic variations, whose overall performance resembled the recurrent parent (Koshihikari). The results revealed that four morphological traits of flag leaf were significantly correlated with each other, while there were no significant correlations with flag leaf SPAD. Using principal component analysis (PCA) and stepwise regression analysis, flag leaf width, flag leaf SPAD, flag leaf length and flag leaf area were selected as the key indexes of D value out of the flag leaf comprehensive evaluation. The results showed that except for tiller number and effective panicle number, the other four traits including plant height, panicle length, basal culm thickness and grain yield per plant were all significantly higher in lines with a higher D value than that in lines with a small D value. A total of 18 QTLs were detected, which were located on chromosomes 1, 4, 7 and 8 with phenotypic variation explained ranging from 4.00% to 28.00% (SPA) and 3.41% to 27.00% (IM), respectively. Except for qFLSPAD1, the other 17 QTLs showed synergistic effect from Bertone alleles. Moreover, a QTL cluster was found in the RM22720–RM404 interval on chromosome 8, containing six major QTLs(qFLL8.1, qFLL8.2, qFLA8.1, qFLA8.2, qD8.1 and qD8.2). 【Conclusion】Flag leaf width, flag leaf SPAD, flag leaf length and flag leaf area were the important indicators that affect the comprehensive evaluation of flag leaf. The flag leaf traits were significantly or extremely significantly positively correlated with the yield per plant. Here we identified 18 QTLs for flag leaf traits and a QTL cluster detected in the RM22720–RM404 interval on chromosome 8, which is an important chromosomal region affecting flag leaf-related traits.