A major gene for low temperature germinability in rice (Oryza sativa L.)

Abstract

Low temperature-induced retardation of seedling growth is a common problem in temperate rice-growing areas, at high altitudes of tropical and sub-tropical areas, and in areas with a cold irrigation water supply. Studies on low temperature germinability have revealed complex inheritance of the trait. The purpose of this study was to identify the gene(s) for low temperature germinability using Italica Livorno as a donor parent. The frequency distributions for the germination rate at 15 °C in the F2 and BC1F1 populations showed continuous segregation, suggesting that low temperature germinability was under polygenic control. Since some lines in the BC1F1 population showed vigorous low temperature germinability similar to that of Italica Livorno, backcrosses until the BC5F1 generation was carried out using Hayamasari as the recurrent parent. Clear segregations of low temperature germinability were observed in the BC5F1 and BC5F2 populations. The distribution of low temperature germinability fitted a single-gene segregation, indicating that a single dominant gene with a large effect was transferred to Hayamasari. This gene is tentatively symbolized as Ltg(t). Low temperature germinability of near isogenic lines for Ltg(t) was similar to that of Italica Livorno. Ltg(t) should greatly contribute to the improvement and manipulation of low temperature germinability in rice breeding programs.