Genetic and biochemical characterization of waxy mutants in cereals

During fine structure analyses of artificially induced waxy mutants in maize by use of Nelson's pollen analysis methods, it was noticed that some mutants showed a phenotype intermediate between waxy and normal nonwaxy. Such intermediate or leaky waxy mutants were frequent among mutants induced by a chemical mutagen, EMS. They seemed to be located evenly within the waxy locus. This would suggest that they might have been missense mutations, which would produce full-sized but partially inactivated enzymes, rather than deletions or frameshift mutations. To confirm the intermediate phenotype, a rapid measuring system was developed to measure waxiness of endosperm quantitatively. It was based on the blue value method and is applicable to a single grain of rice. Among the 27 waxy mutant lines of maize, including 11 EMS-induced, two of the EMS-induced mutants were clearly intermediate. Eighteen EMS induced wx mutants of rice were also examined, and nine were intermediate.