IDENTIFICATION OF 2 OPAQUE2 MODIFIER LOCI IN QUALITY-PROTEIN-MAIZE

Genetic modifiers of opaque2 convert the soft, starchy endosperm of op aque2 maize mutants to a hard, vitreous phenotype, while maintaining t he enhanced lysine content of the grain. Genetic analysis of F2 segreg ating seeds from crosses of opaque2 by modified opaque2 genotypes indi cated that the modifiers are complex traits that act codominantly. We developed two different segregating F2 populations and mapped the modi fier loci by restriction fragment length polymorphism (RFLP) analysis. A relationship was found between formation of vitreous endosperm and the locus encoding the gamma-zein storage protein, which maps near the centromere of chromosome 7. Endosperm modification was consistently a ssociated with the presence of two rather than one gamma-zein gene at this locus. A second modifier locus was mapped near the telomere of ch romosome 7L.