Identification and QTL mapping of important agronomic traits based on rice short-wide grain CSSL-Z752 with restorer line Xihui 18 as background

Rice restorer line is one of the important parents for the utilization of rice heterosis. An excellent restorer line is the basis for breeding super hybrid rice. Rice chromosome segment substitution line (CSSL) based on excellent restorer lines is an ideal material for both genetic research and breeding practice due to its consistent genetic backgrounds besides few substitution segments from donor. Here, a short-wide grain rice CSSL-Z752 was developed using the excellent line Xihui 18 as the recipient parent and Huhan 3 as the donor parent by advanced backcrossing and self-polling combined with simple sequence repeat (SSR) marker-assisted selection. Z752 contained 13 substitution segments from Huhan 3 with 3.69 Mb of average substitution length. Compared with the recipient Xihui 18, the number of effective panicles per plant, grain width, 100-grain weight and yield per plant in Z752 increased significantly, and grain length of Z752 was decreased significantly than that of Xihui 18. The other traits showed no significant difference. Then, the secondary F2 population crossed by Xihui 18 and Z752 was used to map 10 QTLs for the important agronomic traits, which were distributed on the chromosome 2, 3, 4, 5, 6, 7, 10, 11, and 12. Among them, there were two QTLs for effective panicle number per plant, plant height and grain width, respectively, including QPN3, QPN5 and QPH2, QPH6, QGW2, QGW5, and one QTL for grain number per panicle, seed-setting rate, grain length, ratio of grain length to width, respectively, including QGP2, QSSR2, QGL3 and QRLW5. The results will be of great significance for development of single-segment substitution lines carrying target QTL sand breeding of hybrid rice.