Local Adaptation of Maize Landraces to Highland Conditions.

As maize spread out from its center of domestication in the Balsas Valley of Mexico, it experienced diverse climates.  Several lineages of maize differentiated into populations that were adapted to their local environments and/or identified by farmers as having distinct characteristics. These populations are collectively known as landraces.  I hypothesize that landraces from highland elevations are locally adapted to highland conditions. 

Two phenotypes that are commonly seen among highland maize populations are high levels of anthocyanin pigments and the presence of macro-hairs along leaf sheaths.  The dark anthocyanin pigments allow the maize to absorb larger amounts of solar radiation and thus increase the internal temperature faster and to a greater extent.  It is believed that the macro-hairs provide a layer of insulation that traps warmer air next to the plant during the night. 

In addition to the phenotypic adaptations already stated, there may be physiological adaptations that leave no phenotypic traces.  The goal of this study is to measure the fitness of populations of landraces from different regions.  Fitness is a measure of survivability and reproduction.  Due to limited space and resources, plant height was measured as a proxy for fitness.  The experiment consisted of growing four highland populations and two lowland populations of landraces in a growth chamber set to highland conditions.  A reciprocal experiment was done with lowland conditions.  If my hypothesis holds true, then maize breeders looking to select hybrids for higher elevations or cooler climates should consider integrating genetic material from highland landraces into their breeding programs.