Multiple Aleurone And Opaque-2 Mutant Effects On Micronutrient Concentration In Maize
Many resource-poor people who subsist mainly on a maize-based diet suffer from micronutrient deficiency, in particular iron deficiency and niacin deficiency. In response, biofortification has been proposed as a sustainable strategy for micronutrient malnutrition intervention. Motivated by this, we studied the effects of the multiple aleurone layer (Mal ) allele on mineral and total niacin concentrations of maize kernels. We also studied the synergistic effects of Mal with the opaque-2 (o2 ) allele on mineral and total niacin concentrations. For nutritionally important mineral elements, we found no significant effects due to the presence of Mal in BC1S1 kernels from the B8 background. Analyzed across Mo17 and W64A inbred backgrounds using S2 kernels, copper concentration was significantly lower in multiple aleurone versus single aleurone phenotypes. Total niacin assay tested across Mo17 and W64A revealed that multiple aleurone layer kernels had significantly higher total niacin concentration (11.3%). Tested across Mo17o2 and W64Ao2 (in opaque-2 kernels only), magnesium concentration was higher in multiple aleurone versus single aleurone layer phenotype kernels. Potassium concentration was significantly higher in multiple aleurone versus single aleurone layer kernels only in W64Ao2. Within a given aleurone layer phenotypic class and a given inbred background, o2 affected concentrations of various mineral nutrients. There was a numeric trend suggesting interaction between Mal and o2 for iron and sulfur concentrations in Mo17o2 and Mo17O2. There was also a numeric trend suggesting interaction between Mal and o2 for iron and potassium concentrations in W64Ao2 and W64AO2. There was significant interaction for manganese concentration between Mal and o2 in W64Ao2 and W64AO2, with the mal O2 genotype having higher concentration than Mal O2, which in turn was higher than Mal o2. As these differences were non-significant, mostly occured in only one inbred background or contradicting in two backgrounds; or the double mutant showed a significant mineral decrease, they do not provide strong support for breeding for both Mal and o2 mutations to improve maize mineral concentrations. Total niacin concentration was not significantly affected by Mal when tested across Mo17o2 and W64Ao2. The o2 allele increased the niacin concentration in Mo17o2 and W64Ao2 when compared to their non-o2 counterparts within a given aleurone layer phenotypic class. There was a numerical trend suggesting an interaction between Mal and o2 in both Mo17 and W64A backgrounds, with the double mutant having the highest niacin concentration. Although the double mutant was not significantly higher in total niacin concentration than the o2 single mutant, given the heterozygosity remaining in these S2 progenies, the numerical superiority of the double mutant suggests that breeding for both Mal and o2 might have potential to increase total niacin concentration in maize kernels. Our results are limited by the number of inbred backgrounds we were able to work with, the number of ears from each background we were able to assay, and the fact that our progenies had residual background genetic variation (i.e., they were not truly isogenic lines). The evidence for Mal effects and Mal interaction with o2 that affects mineral and niacin concentrations is sufficient to justify further research that minimizes these limitations, in order to more fully understand the potential of these two mutations to enhance maize nutritional value.
dissertation or thesis