Abstract: The aim of the present study is to dissect the genetic factors controlling early growth characteristics of rice (Oryza sativa L.) by QTL analysis. A RIL (recombinant inbred line) population was directly seeded in plastic pots in a randomized complete block. Seedling height (SH) and dry weight (DW) of seedlings were measured at 14, 24, 34 and 44 days after sowing, respectively. Combined with a linkage map based on this population, composite interval mapping was carried out, leading to the identification of 6, 14 and 3 main-effect QTL for DW, SH and 1 000-grain weight (KGW) of the seeds used in the study, respectively. Among these QTL, qGC-3-3 and qGC-5, located within the interval RM148-RM85 of chromosome 3 and the interval RM163-RM161 of chromosome 5, respectively, showed additive effects on multiple measurements of SH and DW in the same direction, but, as the seedlings grew, the magnitude of the effects of QTL qGC-3-3 appeared to have increased while that of QTL qGC-5 seemed to have declined. DW correlated positively with SH (P＜0.01), which was genetically explained by the co-locations of some of the QTL for the two traits with effects in the same direction. Both DW and SH correlated positively with KGW, but the correlation degrees became weaker as the seedlings grew, which was also explained well by the coincidence of the QTL for the traits concerned. In addition, comparison of the QTL detected in the current study with those previously identified for yield related traits with the same population revealed that some of the QTL, such as QTL qGC-3-1 and qGC-3-3 on chromosome 3, seem to produce larger effects on late growth of rice so that they show a greater influence on multiple yield traits, while the others, such as QTL GC-5, show larger effects mainly on early growth. From the point of view of breeding, the former could be better to be used as the potential targets to be manipulated in rice breeding program by marker-aided selection.

Key words: Rice, Dry matter accumulation, Plant height, Quantitative trait loci