Mapping Of Quantitative Trait Loci For Panicle-architecture Traits In Rice

Rice is one of the most important food crops in the world, whose grain-yield is influenced by both sink size and source potential in rice. As the principal sink in rice, panicle- architecture mainly consists of spikelets, panicle axis and primary, secondary and tertiary branches. Thus, understanding the genetic mechanism of panicle architecture traits will be of benefit for improving the panicle architecture and the yield in rice. In this study, the backcross recombinant inbred line(BIL)derived from Koshihikari (japonica) and Kasalath (indica), with different panicle-architecture, were used to study on correlation, path and QTL analysis for total thirty-five panicle architecture traits in rice, including 14 first studied traits in this study, under different environments (Shanghai and Hainan, China). The obtained results were described as follows:1. Normal distribution and transgressive segregation for almost all the traits studied were observed in BIL population, showing that almost all the traits are quantitatively inherited traits. Furthermore there were significant correlations among them.2. A total of 220 QTLs for 35 all panicle-architecture traits were detected, which distributed on all the 12 chromosomes, including 50 for panicle traits, 131 for branch traits, and 39 for grain-shape traits and explained 2.90%~53.24% of total phenotypic variance. Among them, 70 QTLs were reported to associate with 9 of the 14 first studied traits.3. The results showed that the secondary branches play a key role in total number of branches, total length of all branches and number of spikelets (or grains) through correlation and path analyses. In view of qNSB7 on chromosome 7 with contribution to 39.35% of total variance on the number of secondary branches in rice, the locus is valuable for improving the panicle structure and increasing the yield in rice.4. The QTLs controlling panicle traits and branch traits were frequently detected in the same genomic regions, especially in S879-S1513 region on chromosome 3; C1100-C1016 region on chromosome 4; R2171-R2123 and C358-R1167 regions on chromosome 6 and C847-C213 region on chromosome 7, respectively. Undoubtedly, the genomic regions mentioned above were important for panicle architecture.5. Most QTLs affecting grain-shape traits were mainly located around R712- R1843 region on chromosome 2, S10251-C1488 region on chromosome 3, R2232 region on chromosome 5 and C358-R1167 region on chromosome 6. Especially the region on chromosome 6 was also associated with panicle traits and branch traits.From the results of this study, most QTLs detected, directly relative to yield, from Kasalath have positive genetic effects, suggesting that Kasalath possess novel genes prior to Koshihikari for increasing yield in rice. In a word, the results and the tightly linked molecular markers that flank the QTLs detected in the study will be useful in breeding varieties with ideal panicle architecture and higher yield in rice.