The lateness gene
ef2(t), formerly designated as
lf-1, was induced by X-ray irradiation applied to a rice variety Taichung 65. The present study was performed to investigate the allelic relationship between
ef2(t) and two earliness genes,
Efx and
Ef1, and the chromosomal location through trisomic analysis. Rice line T65-ef2(t) carrying gene
ef2(t) was crossed with two tester lines, T65-ER-21 and T65-ER-1 harboring the earliness genes,
Efx and
Ef1, respectively and heading time in the F
2 plants was examined. F
2 plants of the cross T65-ef2(t)/T65-ER-21 showed a trimodal distribution: T65-ER-21 and T65 type, new type and T65-ef2(t) type. The F
2 segregation fitted to a 12: 3: 1 expected ratio. On the other hand, the F
2 plants of the cross T65-ef2(t)/T65-ER-1 exhibited a tetramodal distribution: T65-ER-1 type, T65 type, new type and T65-ef2(t) type, the segregation fitting to a 9: 3: 3: 1 expected ratio. These results suggested that
ef2(t) was non-allelic to both
Efx and
Ef1. Trisomic analysis was performed using seven Triplo lines carrying extra chromosomes 2, 4, 5, 7, 9, 10 and 12, respectively. The trisomics were used as maternal parent for crossing with T65-ef2(t). Heading time in the F
2 plants obtained from self-pollination of F
1 plants (trisomics) was examined. F
2 population derived from a cross between T65-ef2(t) and Triplo 9 showed a typical trisomic segregation pattern, suggesting that
ef2(t) was located on chromosome 9.
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