Abstract:

Gui99, an indica restorer line of hybrid rice (Oryza sativa L.), has been wildly applied to hybrid rice seed production in the south of China, but the genotype of heading date and gene interaction between photoperiod sensitivity loci and basic vegetative growth period in this restorer line are still unknown, which is definitely restricted to the further use of this restorer line in breeding practice and re-production of hybrid seeds. The objective of this study was to make the genetic analysis of Gui99 in photoperiod sensitivity loci and basic vegetative growth period using heading time nearly isogenic lines EG0–EG7, ER–LR, T65, T65m, T65E^b, T65E^bm. The parents, F₁ and F₂ generations from the crosses “heading time nearly isogenic lines×Gui99” grown under high temperature, natural long days and short days treated by sunshade in summer-season at Nanchang (28˚36’ N), Jiangxi province, and under low temperature, natural short days in dry-season at Sanya (18°14’ N), Hainan province, where the average day-length is about 14 h/d, 10 h/d and 11.6 h/d during the course of rice growing, respectively, were analyzed in genotype, temperature sensitivity and gene locus interaction. Experimental results showed that Gui99 carried photoperiod sensitivity alleles E₁, E₂ and E₃ in E₁, E₂ and E₃ loci, respectively, a photoperiod insensitive allele Se-1^e in Se-1 locus and an earliness allele Ef-1 in Ef-1 locus. The genotype of heading date in Gui99 was E₁E₁E₂E₂E₃E₃Se-1^eSe-1^eEf-1Ef-1. The weak photoperiod sensitivity in agronomic characters expressed in Gui99 was caused by the coexisting of late heading time genes E₁ and E₃, earliness gene Ef-1, and gene interaction between E₁, E₃ with Se-1^e. The photoperiod sensitive of late heading time alleles in E loci were enhanced by the photoperiod sensitivity allele Se-1^u (or Se-1ⁿ). The mean days to heading was delayed and the frequency distribution of late heading plants of F₂ population derived from “TLs×Gui99” were increase by the effects of photoperiod sensitivity genes. The genetic foundation of high yield and widely adaptability of hybrid rice combination with this restorer line were also discussed.

Key words: Rice(Oryza sativa L.), Heading time, Photoperiod sensitivity, Basic vegetative growth period, Gene effect, Nearly isogenic line