Genetic improvement of resistance to preharvest sprouting using a major QTL allele for embryo dormancy in rice

Lack of seed dormancy (SD) often causes pre-harvest sprouting (PHS) or inadequate germination in cereal crops and seed production. This research aimed to integrate a dormancy (D) allele isolated from weedy rice at qSD12 into the genetic background of a restoration-of-fertility line (RFL) to mitigate the PHS and germination problems. A hybrid F 2 population was developed to map quantitative trait loci (QTLs) and model their epistatic and genotype-by-environment interactions. Twelve QTLs for flowering time (FT, 3), plant height (5) or SD (4) were identified. Of the 4 SD loci, qSD12 explained most of the phenotypic variance (R 2 = 0.34), and 2 ( qSD3 & qSD6 ) have the D alleles from the RFL. qSD12 interacted with qSD3 or qSD7-2 , with the presence of the D allele at qSD12 increasing the effects of the others, as well as the duration of seed storage at 24 or 40 ˚C for dormancy release. The F 2 plant-derived F 4 to F 6 lines were marker-assisted selected. The major effect of qSD12 on seed germination and on-panicle sprouting was confirmed with the F 4 and F 5 lines, respectively. A sample of F 2 plant-derived backcross (BC 1 F 1 ) plants, which are heterozygous for 2–4 of the SD QTLs, was evaluated for agronomic traits and genotyped with an array of SNP markers. Recurrent backcrossing with the RFL and genomic selection are used to pyramid the D alleles from qSD12 and other locus/loci to develop new varieties and RF lines with improved resistance to PHS.