Phenotypic Identification and Gene Mapping of the Short-panicle and Small-grain Mutant sp18 in Rice through ⁶⁰Co Radiation-induced

A short-spike small-grain mutant sp18 was obtained by ⁶⁰Co radiation irradiated the seeds of the Qiao-gang pearl rice, a japonica rice germplasm resource in Guihzou, of which phenotypic traits were identificated, genetic and molecular marker chain, the whole genome recombinat sequence and mutant gene were analysed. The results showed that compared to the wild-type, the plant-height increased and the effective panicle did not change significantly, but the seed setting rate, panicle length, grain number per-panicle and 1000-grain weight decreased significantly in sp18. By SSR molecular marker analysis, it was found that the markers RM 167 and RM 27150 were linked to the target gene with physical distances of 19.1 cM and 41.5 cM on chromosome 11, respectively. Furthermore, using the genome-wide resequencing to analyze the sp18 and the wild-types, it revealed that sp18 was 322 720 bp（between 7 189 868 bp and 7 512 630 bp） deleted on chromosome 11.The deletion region included Os11 g0235200,Os11 g0235700,Os11 g0235750,Os11 g0236000,Os11 g0236100,Os11 g0236200,Os11 g0237900,Os11 g0238000,Os11 g0238400,Os11 g0238700,Os11 g0239000,Os11 g0239200,Os11 g0239400,Os11 g0239500,Os11 g0240600 and Os11 g0240900,of which Os11 g0235200,encoding peptide transporter, was a cloned short-spike gene SP1. Os11 g0236000 encoded phosphodiester phosphodiesterase family proteins, which participated in auxin signal transduction. And including both Os11 g0239500 and Os11 g0240600 encoded gibberellin receptor GID1 L 2, which participate in the regulation of gibberellin. Therefore, the sp18 was a new allele of sp1. However, it was speculated that the sp18 mutant eventually exhibitted a similar but different mutant phenotype from sp1 due to the large fragment deletion, including multiple genes related to plant hormones.