Fine Mapping of the Giant Embryo Gene GE2 in Rice

Abstract

Giant embryo rice enriched with micro-nutrients can promote nutrition level of rice, and breeding of giant embryo rice is an important task. A new giant embryo variety, Tainung 78 developed by mutagenesis breeding, exhibits similar phenotypes of agronomic traits but 3~5 fold large embryo size to those of its derived parent, Tainung 72. After linkage analysis of 46 F2 individuals of TNG 78 × TCS 17, the mutated gene conferring giant embryo was coarsely mapped in the interval between RM243 and RM420 on the long arm of chromosome 7, which was different position from the GE, and was temporally named as GE2. By employing additional 87 F2 individuals and 5 markers to fine map GE2, the chromosome segment encompassing GE2 was confined to 170 kb and contained 24 candidate genes after annotation. High resolution mapping by using more individuals and markers and sequencing the candidate genes are subjected to touch the target gene. Once GE2 isolated via this positional cloning strategy, we can elucidate the mechanism of GE2 how it enlarges embryo size under gene function and regulation. In the meanwhile, the two flanking markers of GE2, CH0709 and CH0720, are subjected to rice breeding programs to breed more giant embryo varieties. Furthermore, we are attempting to pyramid GE2 and the golden rice gene of Tainung 76, GR1 to purple rice CNY941201, to promote the nutrition of rice.