The discovery,genetic analysis and gene mapping of earliness rice (Oryza sativa L.) D64B.

D64B,an achromatic early mutation,was discovered from indica rice preserver line D63B.D64B were crossed with inhomogeneous sterile lines,preserver lines and restorer lines,most of their F_1 shared the same heading dates as D64B.The results indicated that D64B possessed the characteristic of dominant earliness.To analyze the earliness trait,positive and negative crosses F_2 and BC_1 from the cross of D64B and Shuhui 527 were cultivated.Their heading dates showed double apices distributing with same apex values.According to (apex) vale value-103 d,plants of the F_2 and BC_1 were separated into early plants and late plants,which were tested with χ~2 value.The results suggested that the segregation ratio of number of early to late plant fitted to (3∶1) and 1∶1 for positive and negative cross F_2 and BC_1,respectively,and that the earliness of D64B was controlled by a single dominant major gene.To map the gene,the polymorphisms between D64B and Shuhui 527 was analyzed with reported 356 SSR primers and 59 primers showed polymorphisms.The earliness-lateness near isogenic pools,early plants and late plants from F_2 of Shuhui 527×D64B were further amplified with the 59 primers.The results indicated that there were polymorphisms on both RM279 and RM71.Their results being (analyzed) with MAPMAKER/EXP3.0 software,the dominant major gene was located on the top arm of rice chromosome 2 and between the two SSR markers,RM279 and RM71,with genetic distance of 12.6 cM and 13.3 cM,respectively.According to reported data,the gene was first discovered and tentatively named as Ef-3(t).In breeding practice,sterile line D64A had been bred with D64B.