利用双向导入群体检测遗传背景对耐盐QTL定位的影响

以优质粳稻品种Lemont与高产籼稻品种特青为亲本培育的高代双向回交导入系为材料，在温室140 mmol L^-1 NaCl胁迫条件下定位影响苗期叶片盐害级别(SST)、幼苗存活天数(SDS)、地上部K⁺浓度(SKC)和地上部Na⁺浓度(SNC)及人工气候室条件下影响地上部K⁺、Na⁺浓度的QTL。双向导入系的大部分遗传背景与各自的受体亲本相同，其中Lemont背景导入系中轮回亲本Lemont的基因组平均占83.8%，特青背景导入系中轮回亲本特青基因组平均占88.9%。各耐盐相关性状在两个背景群体中均出现超亲分离，多数性状的频率分布呈相互重叠状态，表明双亲作为供体相互导入各耐盐性状基因的效应大致相当。两个背景导入系群体中分别检测到影响上述耐盐相关性状的QTL各18个，同一性状在两个背景导入系中未能检测到任何相同表达的QTL，表明耐盐QTL表达具有很强的遗传背景效应，同时也说明这些耐盐QTL的效应可能较小。温室和人工气候室两种环境下仅在特青背景导入系中检测到1个影响SKC的相同QTL，表明耐盐QTL与环境的互作非常明显。虽然双亲均表现中等感盐，但QTL定位结果表明双亲中都存在一些提高耐盐相关性状的有利等位基因。研究认为，利用分子标记技术挖掘“隐蔽”于育成品种中的耐盐基因，进一步利用分子标记辅助选择技术对这些非等位耐盐基因进行聚合，完全有可能提高育成品种的耐盐水平。

Genetic Background Effect on QTL Mapping for Salt Tolerance Revealed by a Set of Reciprocal Introgression Line Populations in Rice

QTLs for salt tolerance (ST) related traits including score of salt toxicity of leaves (SST), survival days of seedlings (SDS), shoot K⁺ concentration (SKC) and shoot Na⁺ concentration (SNC) were detected using the reciprocal introgression lines (ILs) derived from a cross between japonica variety “Lemont” and indica variety “Teqing” under salt stress treatment with the concentration of 140 mmol L^-1 NaCL in green house and phytotron. Both genetic backgrounds of the two sets of ILs were similar to their respective parents. On the average, Lemont genome accounted for 83.8% in Lemont background-ILs whereas 88.9% of Teqing genome in Teqing background-ILs. Continuous variation and transgressive segregation for all ST-related traits were observed in the two IL populations with overlaps of frequency distributions for most traits, suggesting the gene effect of reciprocal introgression of the two parents on each ST-related trait was almost equivalent. Eighteen QTLs for all ST-related traits were identified for each of the two IL populations. No any a common QTL for the same trait was detected in the reciprocal IL populations, indicating there was a strong genetic background effect on expression of ST-QTLs, and also suggesting these ST-QTLs had relatively small phenotypic effect. Only one common QTL affecting SKC was identified in Teqing background-ILs under green house and phototron environments, indicating there was a strong interaction of ST-QTL with environment. Although the two parents are moderately susceptible to salt stress, QTL mapping results indicated that some favorable alleles beneficial to improvement of ST-related traits do exist in the parents. Therefore, it is possible to develop a new variety with improved ST by identifying and mining this kind of “hidden” ST-genes existed in the modern varieties through molecular marker technology and further pyramiding these non-allelic alleles via marker-assisted selection.