Department of Agronomy, National Chung Hsing University, Taichung, Taiwan 400, China
The gene Ef-1 for early maturity (abbreviated as E) controls the basic vegetative period, and is distributed in various early-maturing Japonicas including a photo-period-sensitive one such as Kissin (Tsai and Oka 1966). Sato and Hayashi (1985) pointed out that this gene was distributed in many rice cultivars of Japan. By using isogenic lines of Taichung 65 (abbr. T65, photoinsensitive), we detected a recessive and at least five dominant alleles at this locus, viz., e (carried by T65), Ea and Ea-1 (from donor Tatung- tsailai), Eb (from donor Bozu 5), Ex (from an X-ray induced mutant of T65), and Er(from a gamma-ray induced mutant of T65). Sato and Nakasone (1985) reported that Ef-1 was at the same locus as Ef-2, an earliness gene found in a Japanese local variety, and the locus was on chromosome 7 (Sato 1976). In an F2 population from an Ef-1 x Ef-2 cross, all the plants were early thereby showing that the two genes are allelic. The Ef-2 gene may be tentatively symbolised as Ef-12.
A Philippine glutinous variety of tropical Japonica type, 221 or Inakupa, having glabrous hulls and red pericarp, shows a heading time about two weeks later than that of T65. To assess its late-heading genes, it was crossed with T65 and the F1 plants were backcrossed with T65. The T65 x 221 F1 plants had the same heading time as of T65, and the B1F1 plants segregated into an early-heading type and a T65 type, suggesting than an early-heading gene similar as E was present in this late-heading variety. To examine this possibility, an early-heading B1F3 line, (1)221-E, was crossed with T65(20)Ea having Ea (backcrossed with T65 20 times). The F1 plants headed almost simultaneously with the parents, and the F2 population showed the same range of heading time as of the parents. This indicates that variety 221 had an E allele. Possibly, E alleles are distributed in late-heading varieties of tropical countries.
The gene for late heading of variety 221 seems to be recessive. A late-heading homozygous line was obtained from the B1F2 population, and it was backcrossed with T65, and also with a late-heading mutant line of T65 having lf-1. The latter cross revealed that the late-heading gene of 221 was not allelic with lf-1.
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