Mapping Of QTLs For The Major Rice Grain Qualities By Using Chromosome Segment Substitution Lines

Rice is one of the important crop cereal in the world, and rice quality will directly affect the value of their food and goods. Over the years, scholars on rice research had been focused on increasing production, but paid insufficient attention to the quality of rice. With the increase of people’s living level and the opening of the rice market, quality improvement has become one of the main directions of the rice breeding. In our previous studies, in order to better study the related traits of rice grain quality, In our previous studies, the japonica Nipponbare and indica9311were used as recipient and donor, respectively, to develop a set of chromosome segment substitution lines (CSSLs), and a population with38CSSLs was developed and genotyped using a high-throughput resequencing strategy.Based on the resequencing results, a high-quality physical map was constructed for each CSSL.In this study, with these38CSSLs, the main grain qualities, including amylase content (AC), gel consistency (GC), gelatinization temperature (GT), starch viscosity, taste value, protein content of brown rice or milled rice were analyzed under two environments within two years, and the QTLs for these traits were mapped by using substitution fragments overlap analysis. This study will provide relevant information for molecular assisted selection to improve rice quality. The main results were as followings.1. QTL mapping. Based on the38CSSLs, a total of37QTLs for the above seven traits were detected on ten chromosomes except chromosomes9and11., Among these QTLs, were the QTL number for AC, GC, GT, starch viscosity, taste value, brown rice protein content and milled rice protein content were4,2,4,8,4,7and8respectively, and17QTLs were stable under two environments at two years. Compared with previous studies,14QTLs are consistent with the reportsof other scholars,and23QTLs are newly mapped, namely qACl-1, qAC2-1, qGC5-1, qGC10-1, qGT2-1, qGT8-1, qSBV2-1, qSBV7-1, qPKV12-1, qPKV12-2, qTV4-1, qTV10-1, qTV5-1, qTV5-2, qMRPC1-1, qMRPC3-1, qMRPC4-2, qMRPC12-1, qBRPC1-2, qBRPC3-1, qBRPC5-1, qBRPC6-1and qBRPC7-1, respectively We also preliminarily analyzed the additive effect and additive effect contribution of each QTL.2. Pleiotropy of QTLs.The results showed that there is pleiotropy on at least10mapped QTLs. For examples, qBRPC1-1for brown rice protein content, qMRPC1-2for milled rice protein content and qACl-1for AC were located at the same siteon chromosome1; qAC2-1for AC and qSBV2-1for SBV were located at the same siteon chromosome2; There is the same siteon of chromosome4of qTV4-1for taste value and qMRPC4-2for milled rice protein content; qBRPC6-1for brown rice protein content and qMRPC6-1for milled rice protein were located at the same siteon chromosome6; The same siteon is in chromosome12, and they are qHPV12-1for HPV, qSBV12-1for SBV and qGT12-1for GT.3. Futher mapping of selected QTLs. By using136CSSLs containing smaller substitutied segment derived from the above57lines, the mapped region for six stable QTLs were further narrowed. The region for qGC5-1was narrowed from1.3Mb to0.2Mb; qGT12-1fragment size reduced about from11.0Mb to4.4Mb; qBRPC4-1, qBRPC5-1and qBRPC6-1fragments size reduced about from7.4Mb to2.8Mb,6.0Mb to3.5Mb,20.4Mb to5.4Mb, respectively; In addition, qMRPC4-1and qBRPC4-1have the same QTL sites, qMRPC4-1aslo reduced about from7.4Mb to2.8Mb.