Wide variability in kernel composition, seed characteristics, and zein profiles among diverse maize inbreds, landraces, and teosinte

Abstract

All crop species have been domesticated from their wild relatives, and geneticists are just now beginning to understand the consequences of artificial (human) selection on agronomic traits that are relevant today. The primary consequence is a basal loss of diversity across the genome, and an additional reduction in diversity for genes underlying traits targeted by selection. An understanding of attributes of the wild relatives may provide insight into target traits and valuable allelic variants for modern agriculture. This is especially true for maize (Zea mays ssp. mays), where its wild ancestor, teosinte (Z. mays ssp. parviglumis), is so strikingly different than modern maize. One obvious target of selection is the size and composition of the kernel. We evaluated kernel characteristics, kernel composition, and zein profiles for a diverse set of modern inbred lines, teosinte accessions, and landraces, the intermediate between inbreds and teosinte. We found that teosinte has very small seeds, but twice the protein content of landraces and inbred lines. Teosinte has a higher average alpha zein content (nearly 89% of total zeins as compared to 72% for inbred lines and 76% for landraces), and there are many novel alcohol-soluble proteins in teosinte relative to the other two germplasm groups. Nearly every zein protein varied in abundance among the germplasm groups, especially the methionine-rich delta zein protein, and the gamma zeins. Teosinte and landraces harbor phenotypic variation that will facilitate genetic dissection of kernel traits and grain quality, ultimately leading to improvement via traditional plant breeding and/or genetic engineering. Abstract All crop species have been domesticated from their wild relatives, and geneticists are just now beginning to understand the consequences of artiWcial (human) selection on agronomic traits that are relevant today. The primary consequence is a basal loss of diversity across the genome, and an additional reduction in diversity for genes underlying traits targeted by selection. An understanding of attributes of the wild relatives may provide insight into target traits and valuable allelic variants for modern agriculture. This is especially true for maize (Zea mays ssp. mays), where its wild ancestor, teosinte (Z. mays ssp. parviglumis), is so strikingly diVerent than modern maize. One obvious target of selection is the size and composition of the kernel. We evaluated kernel characteristics, kernel composition, and zein proWles for a diverse set of modern inbred lines, teosinte accessions, and landraces, the intermediate between inbreds and teosinte. We found that teosinte has very small seeds, but twice the protein content of landraces and inbred lines. Teosinte has a higher average alpha zein content (nearly 89% of total zeins as compared to 72% for inbred lines and 76% for landraces), and there are many novel alcohol-soluble proteins in teosinte relative to the other two germplasm groups. Nearly every zein protein varied in abundance among the germplasm...

Agronomic and Kernel Compositional Traits of Blue Maize Landraces from the Southwestern United States

“…The protein and oil contents of the southwestern maize accessions, except Flor del Rio, were higher than those of Ohio Blue. Flint-Garcia et al (2009) showed that many maize landraces were higher in protein and oil than modern inbreds. Protein and oil values of landraces thus would appear to be higher than those reported for Corn Belt hybrids in multiple studies (Watson, 2003;Belyea et al, 2004;Dudley et al, 2007;Jaradat and Goldstein, 2013) and quality protein maize hybrids (Zarkadas et al, 2000).…”

Genetic Analysis of Teosinte Alleles for Kernel Composition Traits in Maize

“…parviglumis ) in southern Mexico ∼7500–9000 years ago (Matsuoka et al 2002; Piperno et al 2009; Hufford et al 2012) but bears striking morphological differences in terms of plant, inflorescence, and seed architecture (Doebley et al 1995). Today, maize breeders and geneticists are well aware of the reduction in genetic diversity during crop domestication, especially in genes underlying traits that were targeted by the selection process (Flint-Garcia 2013), which resulted in lower or no variation in traits and limited the discovery of novel alleles that have potential to improve a crop’s germplasm (Flint-Garcia et al 2009). …”

“…Similarly, kernel composition differs between teosinte and modern maize; on a dry matter basis (DMB), inbred maize kernels are ∼71.7% starch, ∼9.5% protein, and ∼4.3% oil (Watson et al 2003). In contrast, teosinte kernels have ∼52.92% starch, ∼28.71% protein, and ∼5.61% oil, strongly suggesting that the increase in kernel size, fruitcase-less kernels, and increase in kernel starch were the targets of artificial selection during maize domestication (Flint-Garcia et al 2009). …”

Comparison of American and European maize (Zea mays L.) protein profiles

“…Maize seeds contain ~10% proteins and ~70% of them are classified as storage proteins. Based on their solubility in different solvents, endosperm proteins are divided into four groups: albumins, globulins, glutelines, and prolamins (Flint-Garcia et al, 2009;Wu and Messing, 2014). Genetic purity and verity identification of maize can be carried out effectively through sodium dodecyl sulphate polyacrylamide gel electrophoresis -SDS-PAGE (Khan et al, 2013).…”