UC Davis

A Minor Role for Environmental Adaptation in Local–Scale Maize Landrace Distribution: Results from a Common Garden Experiment in Oaxaca, Mexico. Agronomists usually assume that yield is a primary selection trait for farmers practicing traditional agriculture. They hypothesize that the landraces grown in farmers’ fields produce higher yields than other local landraces would, if grown in the same fields. We test this hypothesis in experimental gardens using maize landraces grown by indigenous farmers in a low– to mid–elevation region in Oaxaca, Mexico. We selected four villages, two Chatino and two Mixtec, two in low and two in middle elevations. We planted reciprocal common gardens in each village, in order to test whether or not local maize landraces were higher yielding in their respective villages—a finding that would suggest they are selected because they are better adapted to local conditions than landraces from other villages. We also tested resistance to a fungal disease (ear rot caused by Fusarium) that is cited by farmers in the region as a major problem for maize production. We found that maize samples planted in their villages of origin did not in general have higher yields than samples from other villages. There are significant interactions among common garden site, fertilizer use, and seed source. We found that landraces from the Chatino lowlands village perform well in most sites, with and without fertilizer. Regarding ear rot, there is some evidence that landraces are less susceptible when grown away from their villages of origin. These results suggest that social factors, such as seed networks and ethno–linguistic membership, may be more important than local environmental adaptation in determining the distribution of landraces in this region.