CHROMOSOMAL LOCALIZATION AND GENOMIC ORGANIZATION OF ALPHA-AMYLASE GENES IN RICE (ORYZA-SATIVA L)

Genes for alpha-amylase, alcohol dehydrogenase, and Em, an ABA-regulated gene expressed late in embryogenesis, were localized on rice chromosomes by the analysis of primary trisomics. The validity of the mapping approach was confirmed using Adh-1 as a control. The Adh-1 gene has previously been assigned to chromosome 11 using conventional techniques. In this study we confirm this assignment and report an additional locus for alcohol dehydrogenase (Adh-2) on chromosome 9. The alpha-amylase genes were located on chromosomes 1, 2, 6, 8, and 9 while the Em gene was mapped to chromosome 5. To facilitate trisomic analysis and correlation of cloned genes with bands observed on Southern blots, a nomenclature for the rice alpha-amylase genes has been proposed. In addition to mapping nine cloned alpha-amylase genes, we have identified two previously uncloned alpha-amylase genes as part of this study. Polymorphism for alpha-amylase genes belonging to each of the three subfamilies was observed between M202 and IR36. The maximum degree of polymorphism was found among genes belonging to the RAmy3 subfamily, which also has the most diverse group of genes.