Abstract
Seed dormancy is one of important agronomic traits of rice as well as other cereal crop species, because it is associated with pre-harvest sprouting. Seed dormancy is a typical complex trait determined by a series of quantitative trait loci (QTLs). Previously, five QTLs have been detected for the seed dormancy of rice using Nipponbare (japonica)/Kasalath BILs. Here we demonstrate molecular cloning of a major QTL designated as Seed Dormancy 4 (Sdr4). High-resolution mapping enabled to define a genomic region of 8.7-kb as a candidate for Sdr4. Expression analysis showed that predicted gene 1 and 2 were expressed in the panicles. Introduction of 3.3-kb fragment encompassing the predicted gene 2 alone complemented Sdr4 function, indicating that Sdr4 is the predicted gene 2. An Arabidopsis T-DNA tagged line of Sdr4 homologue showed lower germination ratio, suggesting that function of Sdr4 or its homologues in seed dormancy/germination was conserved across monocots and dicots.
