Maize, the staple crop for essentially all the countries in the Americas and for many in Africa, is the most widely cultivated cereal in the world. It is particularly important in Mexico, stemming from its domestication here some 10,000 years ago. Despite the fact that about two thirds of the continental surface of the country is arid or semiarid, thus marginal for agriculture, numerous maize varieties are cultivated essentially in every region of this megadiverse country. However, conversion of cropland, climate change, demographic shift towards urbanization, migration, and a subsequent loss of traditional cultures threaten the very high genetic diversity found in this country. Because annual rainfall is likely to decrease by 15% in ample regions of the country, agricultural adaptation measures that favor the persistence of heirloom maize are of particular interest. This work addresses how traditional producers are likely to respond to a drier climate. In addition, various ecophysiological tools including metabolite characterization and quantification, seed germination, and seedling vigor, were experimentally evaluated for heirloom maizes from contrasting environments in Michoacán, México, to determine their potential for the rapid screening of drought tolerance for maize.
Traditional farmers are likely to adapt through the spontaneous adoption of varieties originated in warm and dry locations, as it was observed in San Francisco Pichátaro, Michoacán. With respect to the ecophysiological assessment, seedling water content, dry mass accumulation, and proline content increased with the aridity of the maize’s site of origin. In turn, parameters that were not adequate predictors of drought tolerance included chlorophyl content that decreased with plant age, polyphenols that accumulated during recovery from drought, and water and temperature requirements for germination that did not vary among maizes. Maize production is predominantly conducted in small subsistence operations that rely on weather, thus potential responses that maintain food security in rural areas requires both the conservation of traditional cultural practices and the adoption and development of climate-ready varieties.