A novel waxy allele in sorghum landraces in East Asia

A loss of granule‐bound starch synthase I (GBSS I) activity results in starch granules that contain mostly amylopectin and little or no amylose, a phenotype described as waxy. Previously, two phenotypic classes of waxy alleles, wx^a, associated with no detectable GBSS I, and wx^b, associated with apparently inactive GBSS I in the endosperm, were reported in sorghum (Sorghum bicolor (L.) Moench). In this study, the waxy alleles in a sorghum core collection were investigated using DNA markers. Of the 337 sorghum accessions examined, 17 accessions that were confirmed to be waxy by a negative iodine staining result and 16 were found to be wx^a. A novel waxy allele, wx^c, was found in a Taiwanese landrace. This allele consists of a +1G to C mutation in the 5′ splice site at the intron 10–exon 11 boundary, a mutation that most likely resulted in the suppression of GBSS I gene expression. A DNA marker specific for wx^c was produced to distinguish the wx^c allele from other alleles, allowing the identification of heterozygous non‐waxy plants.