Identification and Fine Mapping of a Semidwarf Gene <I>iga-1</I> in Rice

Abstract

A semidwarf gene iga-1 of rice (Oryza sativa L.) by mutagenesis of outer space treatment from Texianzhan 13 was identified. The dwarf lines CHA-2 and CHA-2N which carried iga-1 showed great variation in agronomic traits. On the basis of the internode length of CHA-2 and CHA-2N, the mutant belongs to the dn type of dwarfing. GA 3 treatment, endo-GA 3 measurement and α-amylase activity analysis in endosperm showed that iga-1 is independent of gibberellin acid. Using a large F 2 population derived from a cross between the CHA-2 and an japonica rice variety, 02428, the iga-1 gene was fine mapped into a 32.01 kb physical distance between two InDel markers, DL18 and DL19 on chromosome 5, where five open reading frames were predicted, one of which was the rice gibberellin-insensitive dwarf mutant gene D1. Sequence analysis showed that no variation in D1 locus was detected among CHA-2, CHA-2N and Texianzhan 13. Thus, D1 can not be the candidate gene of iga-1. Comparing the other dwarf genes on chromosome 5 showed that iga-1 is possibly allelic to the semidwarf gene sd-7.