Gene dosage effects on carotenoid concentration in maize grain

Yellow maize (Zea mays L.) is the main source of pro-vitamin A carotenoids in food and feed rations. Pro-vitamin A is a precursor to vitamin A in maize grain. Two classes of carotenoid pigments in maize are carotenes and xanthophylls which impart yellow or orange color to endosperm. Pro-vitamin A activity results from beta-carotene and to a lesser degree beta-cryptoxanthin in maize. Yellow endosperm maize color is partly controlled by the yellow endosperm-1 locus (chromosome 6). Dominant Y1 allele results in yellow endosperm pigment and recessive y1 results in a lack of endsperm color. increased levels of carotenoids in maize grain, because of their antioxidant activity, should increase the nutritive value of maize. Research information is needed for breeding programs with the objective to increase carotenoid levels in maize. To obtain some of this information two experiments were conducted: 1. Determine dosage effects at the Y1 locus on five carotenoids using one white, four yellow, three orange and one pale-yellow endosperm inbreds; 2. Estimate maternal and paternal genotype effect on the concentration of five carotenoids using a set of five genotypes. Results from the dosage study showed a consistent increase in the concentration of lutein, zeaxanthin, beta-cryptoxanthin and total carotenoids when each additional dominant Y1 allele was added to the endosperm with the highest concentration at three doses. beta-carotene had the highest concentration at two closes of the Y1 allele. Orange endosperm genotypes had a considerably higher concentration of zeaxanthin than yellow or pale-yellow inbreds. Reciprocal crosses of three generations, F1, backcross-1, and F2, for five genotypes were evaluated for maternal and paternal effects for two years (1998, 1999). In general, carotenoid levels of the different generation crosses are closer to the high parent in value for all the carotenoids evaluated. However, some variation in carotenoid levels among the different genotypes was observed. This variation among different genotypes was due to different concentration levels in the parents. Results using this set of genotypes show that when comparing hybrids with different carotenoid concentrations good estimates of carotenoid levels can be obtained from open pollinated seed because of the larger maternal effect on carotenoid levels.