Domestication and evolution of maize

Abstract

Around ten thousand years ago, men mostly relied on hunting and gathering activities before shifting to agriculture and allied practices. By 4000 years ago, ancient people had completed the domestication of all major crop species upon which human survival is dependent, including rice, wheat, and maize. Recent advances have started to point out the genes that were responsible for this change of the cultivated maize crop. The list of genes to date tentatively suggests that diverse plant developmental pathways were the targets of Neolithic “genetic tinkering,” Maize and its closest wild relatives, the teosintes, present a paradox. Even though maize and the teosintes exhibit extreme differences in their adult morphologies their genomes are so similar that they share the same chromosome number, similar or identical chromosome morphologies, and they can be easily cross-hybridized. A very high level of diversity exists among the maize landraces to explain this diversity many workers have proposed that maize landraces were the products of multiple independent domestication from their wild relative. Reports indicate that all maize arose from a single domestication in southern Mexico about 9,000 years ago. This phylogenetic work is consistent with a model based on the archaeological record suggesting that maize was the result of early Holocene domesticates. A few major genes or multiple linked minor genes on the maize chromosome largely govern the drastic change that is seen between teosinte and maize. Genes like teosinte branched1 (tb1) gene, teosinte glume architecture1 (tga1) and Zea Floricaula / Leafy2 (zfl2). There still remain some untold chapters in the origin and early diversification of maize. These questions will require additional archaeological and botanical exploration, more powerful molecular analyses, and perhaps DNA analysis of archaeological materials such that a perfect phylogenetic relationship can be established.