MAIZE AMINO ACID PATHWAYS MAINTAIN HIGH LEVELS OF GENETIC DIVERSITY

The methods commonly used to determine the genetic bases of agronomic traits rely on genetic variation to detect marker-phenotype associations. If variation at key loci is reduced due to selection during domestication, the analyses may fail to identify these genes as important loci in controlling trait expression. It is of practical importance to determine the level of genetic diversity for key genes controlling agronomic traits. Results from recent large scale selection screens in maize have revealed that a number of genes involved in amino acid synthesis exhibit signs of selection. Here we asked whether other genes in amino acid pathways were targets of selection, and to what extent amino acid metabolism has experienced artificial selection. We surveyed amino acid pathways by sequencing 15 candidate genes involved in amino acid metabolism maize inbreds and teosinte, and conducted tests of selection. We demonstrated that five of 15 additional genes involved in amino acid metabolism exhibit weak evidence for selection. Amino acid synthesis pathways, as a whole, do not show evidence of greatly reduced genetic diversity. Our results suggest that adequate genetic diversity remains for improvement of maize nutritional quality, and that limited genetic diversity may be impacting only a few specific amino acids.