Microsatellites polymorphism on the Waxy gene locus and their relationship to amylose content in indica and japonica rice, Oryza sativa L.
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Amylose is synthesized under the catalysis of granule-bound starch synthases (GBSS) encoded by the waxy gene in rice. A polymorphic (CT)n microsatellite sequence was reported within the Wx gene recently. The polymorphism of this sequence and its relationship to amylose content was explored using 74 non-waxy indica and japonica rice varieties or breeding lines. Seven Wx microsatellite alleles, namely (CT)8, (CT)10, (CT)11, (CT)16, (CT)17, (CT)18, and (CT)19 were identified. The distribution difference of these alleles were obvious between indica and japonica subspecies. In indica rice, 92.6% materials were either with (CT)11 or (CT)18, or both of them (heterozygous material) ; remaining ones included 2 with (CT)10, 2 with (CT)8 and 1 with (CT)17. In japonica rice, 18 varieties (lines) were with (CT)16 and (CT)17, which occupied 90.0% of the total, remaining ones were 1 with (CT)18 and 1 with (CT)19. The determinant coefficient [the R squared (R2) value] of (CT)n to amylose content was as high as 0.912, which means 91.2% of amylose content variation could be resulted from waxy gene allele difference. In the experiment, we also found that 6 indica rice materials, 2 of which were commercial varieties, were still heterozygous on the Wx locus with alleles (CT)11 and (CT)18, the implications of this finding to plant genetic study and breeding application were discussed.
