Mexican native maize and highland/acid-soil adapted inbreds

Indigenous people domesticated maize more than 9,000 years ago in a hot, dry, low-elevation region of southwest Mexico. Subsequently, maize dispersed and was successfully established in different environments throughout the Americas and, eventually, across the world. In Mexico alone, 59 different native landraces of maize have been described, cultivated from sea level to an elevation of 3400masl. Mexican highland varieties have adapted to a suite of challenges, including low atmospheric pressure and temperature, frequent frosts and freeze-thaw cycles, high UV-B radiation, seasonal precipitation, and low bioavailability of phosphorus due to the low pH of volcanic soils. Highland maize has to mature and complete grain filling before the first frosts at the end of the growing season. To maximize the length of the growing season, highland farmers sow early, before the onset of the annual rains. Traditionally, seeds are deep planted (10 - 25 cm) to access residual soil moisture and to protect from frost damage. This practice allows varieties that require 160-180 days to reach maturity in the cold of the highlands to be grown in areas with a frost-free season of 90-120 days. Although displaying enhanced phosphorus use efficiency, Mexican highland varieties tend to show restricted root development and, to prevent lodging, plants are hilled (piling of soil around the base of the plant) during vegetative growth.

To support broader efforts characterizing local adaptation in traditional maize varieties, this project presents genome assemblies of the Mexican highland varieties Palomero Toluqueño (collected at 2507masl) and Palomero de Jalisco (2520masl), the Mexican mid-elevation variety Tabloncillo (1355m), the lowland variety Zapalote Chico (50masl), and the CIMMYT inbred lines CML457 and CML459 (highland adaptation) and CML530 (acid soil adaptation)

This project was supported by NSF Award #1546719 and collaboration with CINVESTAV Unidad de Genómica Avanzada (LANGEBIO), Universidad Nacional Autónoma de México (UNAM), North Carolina State University, Iowa State University, UC Davis, Penn State University, USDA-ARS and Corteva Agriscience. We acknowledge the smallholder farmers and indigenous people of the Americas whose work and love for their traditions and identity keep maize genetic variation alive.

References
Eagles HA, Lothrop JE (1994) Highland Maize from Central Mexico - Its Origin, Characteristics, and Use in Breeding Programs. Crop Science 34: 11–19 doi: cropsci1994.0011183X003400010002x

Perez-Limón S, Li M, Cintora-Martinez GC, Aguilar-Rangel MR, Salazar-Vidal MN, González-Segovia E, Blöcher-Juárez K, Guerrero-Zavala A, Barrales-Gamez B, Carcaño-Macias J, et al (2022) A B73×Palomero Toluqueño mapping population reveals local adaptation in Mexican highland maize. G3 (Bethesda). doi: 10.1093/g3journal/jkab447

Information about assembly Zm-ZAP-REFERENCE-HiLo-1.0