Submitted to: Rice Technical Working Group Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 2/1/1996
Publication Date: N/A
Technical Abstract: The waxy gene (wx) encodes the granule bound starch synthase responsible for the synthesis of amylose. Recently, a polymorphic microsatellite sequence closely linked to the waxy gene was reported (Bligh et al., in press). To determine whether polymorphism in this sequence correlates with variation in apparent amylose content, we tested 86 rice varieties representing current and historical long and medium grain U.S. rice germplasm. Seven wx microsatellite alleles were identified which together explain 83.3 percent of the variation in apparent amylose content of the 84 nonglutinous rice varieties tested. Similar results were also obtained with 101 progeny of a cross between a low and an intermediate amylose variety. We sequenced a 200 bp PCR amplified fragment containing the microsatellite and the putative 5' splice site of the wx leader intron from a subset of 45 nonglutinous varieties representing all seven microsatellite alleles. All of the varieties with more than 19 percent amylose had the sequence AGGT a the putative 5' splice site, while all low amylose varieties had AGTT. Interestingly, two varieties in the (CT)17 microsatellite class that differed substantially in amylose content still showed the correlation between the AGGT/AGTT polymorphism and apparent amylose content. This single nucleotide substitution could explain more than 80 percent of the variation in the apparent amylose content of the 45 nonglutinous varieties tested and can be easily assayed by AccI digestion of the amplified fragment. Polymorphism at this site was not, however, able to explain the very low amylose contents of two glutinous varieties tested, both of which had the sequence AGTT at the putative 5' splice site and belonged to the (CT)17 wx microsatellite class.