Isolation and genetic characterization of a fragile plant mutant in rice (itOryza sauva) L.

The fragile rice mutant was isolated from an M₂ population of indica variety Shuang Ke Zao (SKZ) treated with g-rays, and designated as fp1 (fragile plant 1) because of its fragile leaves and culms. To map FP1 locus, an F² mapping population was derived from a cross between the fp1 and C-bao, a polymorphic japonic variety. The primary mapping result places the FP1 locus in an interval between two molecular markers, microsatellite marker RM16 (3.1 cM proximal to FP1) and STS marker G144a (9.1 cM distal to FP1) in the centromere region of chromosome 3. A CAPS marker C524a was further developed between RM16 and G144a, with 0.4 cM genetic distances to the FP1locus, providing a practical starting point for constructing a BAC contig spanning the FP1 locus and cloning the fp1 gene. Allelism test demonstrated that fp1 is allelic to bc1, a fragile rice mutant reported previously.