Allele Mining of Exotic Maize Germplasm to Enhance Macular Carotenoids

Lutein and zeaxanthin are commonly referred to as the macular carotenoids, as they are localized to ocular tissues and their loss is associated with age-related macular degeneration. Thirty-four high-carotenoid (HiC) lines exhibiting uniquely high concentrations of carotenoids resulted from allele mining of the Orange Flint race using traditional breeding techniques and visual selection for deep orange endosperm color. Total carotenoid concentrations of the HiC lines ranged from 50 to 101 μg g ―1 dry weight (DW) with lutein and zeaxanthin concentrations as high as 66 and 65 μg g ―1 DW, respectively, levels higher than reported in previous germplasm surveys. The HiC lines fall into three classes based on the accumulation of the major carotenoid: "high-lutein," "high-zeaxanthin," and "balanced." Significant year effects were observed for carotenoid concentrations but not for profiles. During kernel development the pattern of carotenoid accumulation in the HiC lines did not appear to be different than in yellow corn belt dent lines. Collectively, the HiC lines represented only one y1 haplotype, 10 unique haplotypes of IcyE, and two unique haplotypes at crtRB1. Interestingly, previously identified diagnostic polymorphisms within IcyE did not appear to be useful in distinguishing between high-lutein and high-zeaxanthin HiC lines, and high β-carotene levels were achieved despite the presence of a suboptimal crtRB1 allele. The HiC lines illustrate the utility of mining allelic variation from exotic sources coupled with the power of simple visual selection and the potential limitations of diagnostic polymorphisms.