Segregation analysis of rice seed germination under cold stress using major gene plus polygene mixed inheritance model

One F_2:9 recombinant inbred lines (RILs) population, derived from a cross between IR28 (Oryza sativa L. spp. indica) and Daguandao (japonica), was used to identify germination ability including the traits of imbibition rate, germination rate, germination index, root length, shoot length and seed vigour at 14°C for 23 d. A major gene plus polygene mix inheritance model was also applied to conduct genetic analysis for germination ability. The results showed that the performances of rice seed germination were mostly limited by cold stress and there were significant differences in all germination traits under cold stress among RILs. The frequency distributions of germination traits in RILs population showed continuous segregation, suggesting these were quantitative traits controlled by several genes, and more RILs were skewed to cold sensitive type. The germination traits under cold stress were regulated by two or three major genes plus polygene, and mainly dominated by major genes with high heritability values, accounted for 26.4-95.3% of the total phenotypic variation. Each trait was controlled by the specific genetic model: imbibition rate, root length, shoot length and vigour index controlled by two major genes plus polygene, germination rate controlled by two or three major genes and germination index regulated by two major genes.