Linkage Analysis of a Lateness Gene ef4 in Rice, Oryza sativa L.

Abstract

A near isogenic line T65-LH2 bred from IR8 by five times of successive backcrossing with Taichung 65 (T65) as recurrent parent was found to harbor a lateness gene ef4(t). In the present study, we investigated the allelic relationship between ef4(t) and two earliness genes, Efx and Ef1, followed by linkage analysis to reveal the chromosomal location of ef4(t). T65-LH2 was crossed with two testers, T65-ER21 and T65-ER1 harboring the earliness genes, Efx and Ef1, respectively. F1 plants of the two crosses were raised to obtain F2 seeds. Moreover, the F1 plants were backcrossed with T65-LH2 as to obtain the B1F1 seeds. Heading time in F2 and B1F1 plants as well as parental lines were examined. F2 and B1F 1 plants of the crosses between T65-LH2 and T65-ER21 showed monogenic segregation while F2 and B1F 1 plants obtained from the cross between T65-LH2 and T65-ER1 exhibited digenic segregation. Thus, ef4(t) is allelic to Efx on chromosome 3 and independent of Ef1. Subsequently, linkage analysis of ef4(t) was carried out using three marker genes on chromosome 3, Hg, dl and bc1. T65-LH2 was crossed with the isogenic lines of T65 carrying those marker genes. Heading time and morphological characters in F2 plants and parental lines were observed. Results showed that ef4(t) was linked to Hg and dl with recombination values estimated at 33.2% and 16.8%, respectively, but segregated independently of bc1.