利用9311来源的粳型染色体片段代换系定位控制稻米糊化温度的微效QTL

糊化温度(gelatinization temperature,GT)是评价稻米蒸煮与食味品质的重要因素之一,除受一主效基因控制外,还受多个微效基因的影响。本研究利用粳稻品种日本晴和籼稻品种9311作为受体和供体来源的38个染色体片段代换系为研究对象,于2010—2011年连续2年分别于2个环境内种植,测定各株系稻米的糊化温度(碱消值),利用t测验与轮回亲本比较。结合高通量重测序技术鉴定各代换系的基因型,以一年两地检出的极显著差异位点作为一个QTL,共检测到4个控制GT的微效QTL,即qGT2-1、qGT7-1、qGT8-1和qGT12-1,分别位于第2、第7、第8和第12染色体上。加性效应分析结果显示,4个QTL的效应值均为负值,表明来自籼稻品种9311的这4个片段对碱消值的效应均为负效应。其中qGT7-1和qGT12-1 2个QTL在2年4个环境均被检测到,遗传效应的趋势也一致,加性效应贡献率为11.31%~28.95%。以受体亲本碱消值差异最大的代换系N53株系及亲本为材料,对稻米淀粉精细结构进行分析,推测支链淀粉中短链含量的减少可能会引起GT的升高。上述结果为进一步精细定位和克隆相应QTL及开展稻米品质改良的分子育种奠定了基础。

Mapping of Minor QTLs for Rice Gelatinization Temperature Using Chromosome Segment Substitution Lines from Indica 9311 in the Japonica Background

Gelatinization temperature (GT), one of the determinants for rice cooking and eating quality, is controlled by not only a major gene but also several minor genes. Previously, we used the japonica rice cultivar Nipponbare as the recipient and the indica 9311 as the donor to develop a population containing 38 chromosome segment substitution lines (CSSLs), and genotyped them using a high-throughput re-sequencing strategy. In this study, this population and their parents were used to map the minor quantitative trait loci (QTLs) for rice gelatinization temperature. The GT of each line was measured and expressed as alkali spreading value (ASV) under two environments (Campus and Hangji) within two years (2010–2011). After compared with that of the receptor parent by t-test, the stable QTL was identified if there was a significant difference in both environments of the same year. Finally, four QTLs for gelatinization temperature were detected, named as qGT2-1, qGT7-1, qGT8-1, and qGT12-1 located on chromosome 2, 7, 8, and 12, respectively. Two of them, qGT7-1 and qGT12-1 were stable over two years and in two environments, with contributions ranging from 11.31% to 28.95%. Additive effect analysis showed that the effect value of four QTLs were negative. These results demonstrated that the four fragments from donor parent 9311 had negative effects for the alkali spreading value. Further comparison for starch fine structure between the receptor parent and N53 line showed that the decrease of A and B1 chains with short branch length might be the possible reason for increased GT. The results pave the way for the fine mapping and subsequent cloning of these QTLs and the molecular breeding for the improvement of rice quality.