Abstract: Heading date (HD) is an important agronomic trait in rice. Appropriate heading date is a prerequisite for attaining the desired yield level in rice breeding programs. It is very important for rice improvement to map heading date quantitative trait loci (QTLs). Single segment substitution lines (SSSLs) containing only one segment of donor chromosome are useful tools for precise mapping of QTLs and for the evaluation of gene action. In this research, the QTLs for heading date on the substituted segments of 52 rice SSSLs derived from 6 advanced backcrosses were identified through t-test for means comparisons between SSSLs and the recipient parent Huajingxian 74. QTLs were detected with a significance of P≤0.001. A total of 20 QTLs were identified on 10 rice chromosomes with the exception of chromosomes 5 and 6. The QTL additive effect ranged from -5.9 to 1.1, and the additive effect percentages of the QTLs ranged from -7.4% to 1.4%. Eight QTLs were mapped in intervals less than 10.0 cM. qHD-3-1, a dominant gene for early heading, has been mapped using a F2 population developed from a cross between a SSSL and Huajingxian 74. In mapping population the segregation ratio of early and late heading plants was in accordance with 3:1. qHD-3-1 was located between microsatellite markers PSM304 and RM569 on the short arm of chromosome 3 at genetic distances of 2.4 cM and 5.1 cM, respectively.

Key words: Rice (Oryza sativa L.), Single segment substitution line (SSSL), Heading date (HD), QTL, Gene mapping