Fine Mapping Of Alk, A Gene Responsible For Rice Gelatinization Temperature

Gelatinization temperature(GT) is one of the important parameters for cooking and eating quality of rice. The phenotype, biochemistry and inheritance of GT has been widely studied recently. Fine mapping and isolation of a major gene controlling GT is necessary for improving cooking quality of rice and ensatisfying the demand of food industry.The present investigation revealed that GT was controlled by one gene based on phenotype identification (alkali digestion test) of F2 derived from F1 crossed between an Indica rice variety Shuangke Zao with high GT and a Japonica rice variety C Bao with low GT. GT was found to have little relationship with amylose content(AC). Preliminary mapping of alk (alkali digestion) for GT showed it was linked to SSR marker, rm50 and rm527, and was located on the short arm of chromosome 6. alk was mapped physically within one PAC via further fine mapping. It is a single copy gene and encodes a putative soluble starch synthase II(SSSII) with high homology to Maize SSSIIa. It is expressed only in rice seeds via RT-PCR, and no difference between rice varieties with high GT and those with low GT on transcriptional level. A hypothesis for molecular mechanism for GT variation of rice is presented, that is DNA insertion, deletion or base substitution in coding sequence of alk contributes to GT variation of rice. Complementation test of rice is in progress.