POLLEN-PARENT EFFECTS ON PROTEIN-QUALITY AND ENDOSPERM MODIFICATION OF QUALITY PROTEIN MAIZE

Quality protein maize (Zea mays L.) (QPM) has protein of high nutritio nal value conferred by the opaque-2 (o2) gene and vitreous endosperm b ecause of numerous modifier genes. Superior protein quality is only ex pressed when endosperm tissue is homozygous recessive (o2o2). During Q PM research and development, it is common to evaluate trials in which QPM genotypes randomly interpollinate. We do not know if protein quali ty determinations for entries in such trials are valid measures of wha t would be expressed in a pure stand. In this study, we used nine QPM and three o2 (unmodified, soft endosperm) cultivars as females for six pollen treatments to measure the effect of pollen source on protein c oncentration of grain, tryptophan concentration in grain, tryptophan c oncentration in protein, and endosperm modification (translucency) in three environments. The pollen treatments were four QPM hybrids, one n ormal-endosperm maize cultivar, and self-pollination. Pollen of normal -endosperm maize reduced tryptophan in grain by 37% and tryptophan in protein by 38% but improved endosperm modification of QPM females by 3 6% relative to pollen of QPM males. Pollen of normal-endosperm maize a nd QPM did not differ in effect on protein concentration of grain. Pro tein quality traits did not differ for QPM cultivars pollinated by sel f or by other QPM males. Kernels were slightly more vitreous, however, for females pollinated by other QPM males than for those that were se lf-pollinated. Effects of females were significant (P < 0.01) and the interaction of males x females not significant for QPM entries for all traits. We conclude that it is valid to evaluate QPM germplasm in tri als where entries randomly interpollinate, provided that pollen of nor mal-endosperm maize is excluded.