Genetic dissection of the seed dormancy trait in cultivated rice (Oryza sativa L.)

Seed dormancy is an important trait for the analysis and manipulation of pre-harvest sprouting resistance in rice. This study presents data on dissection of the genetic basis of the seed dormancy character in the indica cultivar N22, which exhibits levels of dormancy highly in excess of traditional rice cultivars. Three simple sequence repeat (SSR)-based linkage maps derived from two BC1-type populations of Nanjing35 (a japonica non-dormant breeding line)/N22//Nanjing35 and USSR5 (non-dormant japonica cultivar)/N22//USSR5, and one F2 population of USSR5/N22, were constructed to detect genes controlling seed dormancy. Five quantitative trait loci (QTLs) for seed dormancy, i.e., qSdn-1, qSdnj-3, qSdn-5, qSdn-7 and qSdn-11, were identified on chromosomes 1, 3, 5, 7 and 11, respectively. The N22-derived alleles were observed to increase the seed dormancy at all the loci except qSdnj-3. Genes conferring seed dormancy in N22 showed incomplete dominance effect. Two QTLs, qSdn-5 and qSdn-11 were detected in the two BC1 populations, while qSdnj-3 and qSdn-7 were only identified in the one BC1 population (Nanjing35/N22//Nanjing35), whereas the QTL qSdn-1 was common in all the three populations. The dormancy trait was expressed whenever any of the dormancy genes presents and can be further improved by pyramiding these genes. Of all QTLs, qSdn-1 provided the most obvious target for marker-assisted selection (MAS) due to its stability for improving rice pre-harvest sprouting tolerance.