Abstract: A chromosome segment substitution line (CSSL) population, derived from the cross of Asominori and IR24 with Asominori as the recurrent parent, was planted and phenotyped for brown rice rate (BR), milled rice rate (MR) and head rice rate (HR) in four sites. QTL for milling quality were characterized and expression stability of these QTL was further investigated by using target CSSLs harboring certain QTL. The phenotypic values of these three traits all showed continuous distributions and transgressive segregations in the CSSL population across the four environments.. Meanwhile, a total of 30 QTL were identified for the three quality traits, among which four QTL, qMR-6、qMR-8、qHR-3 and qHR-6, were all consistently detected in the four different environments. Moreover, phenotypic values were different significantly (P<0.05) between Asominori and the target CSSLs harboring any of the four QTL alleles, indicating expression stability of the four QTL was relatively higher. In addition, QTL qMR-8、qBR-8b and qHR-8 were co-located in the G1149-R727 interval on chromosome 8 carrying a QTL cluster. Interestingly, many major QTL affecting rice eating, cooking, appearance and nutrient quality was also mapped into the QTL cluster in our previous studies. These results thus obtained provide us a good chance to elucidate the complex mechanism that formation of many rice quality traits was simultaneously controlled by a gene or a gene cluster on chromosome 8.

Key words: Rice (oryza stativa L.), Milling quality, Chromosome Segment Substitution Line (CSSL), QTL mapping, expression stability