A B73 x palomero toluqueño mapping population reveals local adaptation in Mexican highland maize

Authors: PEREZ-LIMON, SERGIO - Pennsylvania State University; LI, MENG - Pennsylvania State University; CINTORA-MARTINEZ, G. CAROLINA - Langebio Cinvestav; AGUILAR-RANGEL, M. ROCIO - Langebio Cinvestav; SALAZAR-VIDAL, M. NANCY - Langebio Cinvestav; GONZALEZ-SEGOVIA, ERIC - Langebio Cinvestav; BLÖCHER-JUÁREZ, KARLA - Langebio Cinvestav; GUERRERO-ZAVALA, ALEJANDRO - Langebio Cinvestav; BARRALES-GAMEZ, BENJAMÍN - Langebio Cinvestav; CARCAÑO-MACIAS, JESSICA - Langebio Cinvestav; COSTICH, DENISE - International Maize & Wheat Improvement Center (CIMMYT); NIETO-SOTELO, JORGE - Universidad Nacianal Autonoma De Mexico; MARTINEZ-DE LA VEGA, OCTAVIO - Langebio Cinvestav; SIMPSON, JUNE - Langebio Cinvestav; HUFFORD, MATTHEW - Iowa State University; ROSS-IBARRA, JEFFREY - University Of California, Davis; Flint-Garcia, Sherry; DIAZ-GARCIA, LUIS - Instituto Nacional De Investigaciones Forestales Y Agropecuarias (INIFAP); RELLÁN-ÁLVAREZ, RUBÉN - North Carolina State University; SAWERS, RUAIRIDH - Pennsylvania State University

Submitted to: G3, Genes/Genomes/Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/16/2021
Publication Date: 1/3/2022
Citation: Perez-Limon, S., Li, M., Cintora-Martinez, G., Aguilar-Rangel, M., Salazar-Vidal, M., Gonzalez-Segovia, E., Blöcher-Juárez, K.A., Guerrero-Zavala, A., Barrales-Gamez, B., Carcaño-Macias, J.L., Costich, D.E., Nieto-Sotelo, J., Martinez-De La Vega, O., Simpson, J., Hufford, M.B., Ross-Ibarra, J., Flint Garcia, S.A., Diaz-Garcia, L., Rellán-Álvarez, R., Sawers, R.J. 2022. A B73 x palomero toluqueño mapping population reveals local adaptation in Mexican highland maize. G3, Genes/Genomes/Genetics. 12(3). Article jkab447. https://doi.org/10.1093/g3journal/jkab447.
DOI: https://doi.org/10.1093/g3journal/jkab447

Interpretive Summary: Farmers have passed down family varieties of corn for hundreds of years across the Americas. The results are varieties adapted to specific environmental conditions, including highland field sites located a mile or more above sea level. One such locally adapted variety is a popcorn called “Palomero Toluqueno,” which literally means “popcorn from Toluca,” a highland region near Mexico City. In this study, we created a new experimental population by crossing Palomero Toluqueno with a corn from Iowa, and evaluated the population in low and high elevation field sites to study highland adaptation. We found several gene regions that control adaptation traits that lead to grain yield. One such gene region had opposite effects on yield in the low and high elevation field sites, which suggests that highland adaptation has evolved at the cost of yield. The findings of this study shed light into how corn has adapted to the high elevation environment in the past, and how corn may be able to adapt to different environmental changes in the future with increased yield.

Technical Abstract: Generations of farmer selection in the central Mexican highlands have produced unique maize varieties adapted to the challenges of the local environment. In addition to possessing great agronomic and cultural value, Mexican highland maize represents a good system for the study of local adaptation and acquisition of adaptive phenotypes under cultivation. In this study, we characterize a recombinant inbred line population derived from the B73 reference line and the Mexican highland maize variety Palomero Toluque~no. B73 and Palomero Toluque~no showed classic rank-changing differences in performance between lowland and highland field sites, indicative of local adaptation. Quantitative trait mapping identified genomic regions linked to effects on yield components that were conditionally expressed depending on the environment. For the principal genomic regions associated with ear weight and total kernel number, the Palomero Toluque~no allele conferred an advantage specifically in the highland site, consistent with local adaptation. We identified Palomero Toluque~no alleles associated with expression of characteristic highland traits, including reduced tassel branching, increased sheath pigmentation and the presence of sheath macrohairs. The oligogenic architecture of these three morphological traits supports their role in adaptation, suggesting they have arisen from consistent directional selection acting at distinct points across the genome. We discuss these results in the context of the origin of phenotypic novelty during selection, commenting on the role of de novo mutation and the acquisition of adaptive variation by gene flow from endemic wild relatives.