Interaction of Genetic Mechanisms Regulating Methionine Concentration in Maize Grain

Abstract

Methionine is a limiting amino acid in poultry diets, so methionine supplementation is typically required to meet nutritional demands. Maize (Zea mays L.) varieties with increased methionine levels have been developed using three different approaches: (i) increased levels of the methionine‐rich 10‐kDa zein, (ii) disruption of protein deposition using the floury‐2 allele, and (iii) recurrent selection. The goal of this study was to characterize the interactions of these three mechanisms for increasing methionine to develop optimal breeding strategies for this limiting amino acid. A complete diallel mating design was used to produce all possible hybrid combinations, which were analyzed by Griffing's experimental Method 3, Model 1. Grain samples were analyzed for methionine concentration using a microbial method. The significantly negative general combining ability (GCA) for inbred RS2 suggests it did not perform well in hybrid combination, while the significant specific combining abilities (SCAs) suggest that some specific combinations of mechanisms worked well together in this germplasm. Analysis of grain quality traits by near‐infrared spectroscopy (NIRS) revealed that the high‐methionine hybrid combinations had starch and oil concentrations similar to all other hybrids but had elevated protein concentrations. In some hybrids in this study, dzr1 and recurrent selection were effective mechanisms to elevate methionine in hybrid combination and did not have an associated yield penalty relative to other hybrids produced in the study, which supports their use in a high‐methionine maize breeding program.

Interaction of Dzr1, Opaque-2 and Normal Endosperm Maize Inbred Lines for Grain Yield and Protein Quality

“…High narrow (0.75) and broad (0.85) sense heritability values suggest protein concentration can be improved via breeding. High additive gene effects for methionine revealed by Huffman et al (2016) are consistent with our results related to methionine heritability.…”

“…Darrigues et al (2005) reported a methionine concentration of 0.210 g / 100 g, in the dzr1 inbred B101. Huffman et al (2016) found this value to be 0.179 g / 100 g in hybrids in diallel crosses in which some parents contained dzr1. Although the findings were similar, relatively higher results were obtained from our study.…”

“…Although the findings were similar, relatively higher results were obtained from our study. A microbial method was used to determine the amount of methionine in Darrigues et al (2005) and Huffman et al (2016). In our study, a high resolution chromatographic (LC-MS / MS) method was used.…”

“…These observations suggest that use of the opaque-2 gene in maize in poultry feed might increase the methionine supplementation requirement. Huffman et al (2016) used a diallel study to investigate interaction of genetic mechanisms between floury-2 and dzr1. Interaction among opaque-2 which is the most widely used lysine modification mutation, and dzr1 may help in breeding for these traits.…”