Molecular analysis of genetic diversity in a Texas maize (Zea mays L) breeding program

The Texas maize (Zea mays L) breeding program at Texas A&M University has been unique among breeding programs for the incorporation of diverse germplasm from a wide range of origins into elite inbred lines. The Texas program, situated in a subtropical environment, has found beneficial traits in maize of tropical origin beyond what is available in the temperate material commonly used in the far more productive Midwestern region of the United States. To date, no molecular studies had been conducted to make any quantitative differentiations between the genetic diversity in the germplasm developed in the Texas program or comparisons to the germplasm available from the Midwest. In this study, a molecular characterization of genetic diversity was performed. A unique set of 266 elite Texas lines were genotyped using 766 single nucleotide polymorphism markers, this was then combined with data published in a previous study focusing on ex-PVP lines released by private companies. The two data sets combined had 380 genotypes with 635 markers. It was determined that there were five subpopulations of material in this combined set as demonstrated by population structure. The data suggested that the array markers, designed to cluster the Midwestern heterotic groups, did not discriminate this exotic material well and/or that the Texas heterotic pools were not well supported. We conclude that the majority of Texas program material is a novel population, genetically dissimilar to Midwest temperate material, and would be a useful source of unique genetics for other maize breeding programs.