Hallauer's Tusn: a decade of selection for tropical-to-temperate phenological adaptation in maize.
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Crop species exhibit an astounding capacity for environmental adaptation, but genetic bottlenecks resulting from intense selection for adaptation and productivity can lead to a genetically vulnerable crop. Improving the genetic resiliency of temperate maize depends upon the use of tropical germplasm, which harbors a rich source of natural allelic diversity. Here, the adaptation process was studied in a tropical maize population subjected to 10 recurrent generations of directional selection for early flowering in a single temperate environment in Iowa, USA. We evaluated the response to this selection across a geographical range spanning from 43.05 (WI) to 18.00 (PR) latitude. The capacity for an all-tropical maize population to become adapted to a temperate environment was revealed in a marked fashion: on average, families from generation 10 flowered 20 days earlier than families in generation 0, with a nine-day separation between the latest generation 10 family and the earliest generation 0 family. Results suggest that adaptation was primarily due to selection on genetic main effects tailored to temperature-dependent plasticity in flowering time. Genotype-by-environment interactions represented a relatively small component of the phenotypic variation in flowering time, but were sufficient to produce a signature of localized adaptation that radiated latitudinally, in partial association with daylength and temperature, from the original location of selection. Furthermore, the original population exhibited a maladaptive syndrome including excessive ear and plant heights along with later flowering; this was reduced in frequency by selection for flowering time.
author list (cited authors)
Teixeira, J., Weldekidan, T., de Leon, N., Flint-Garcia, S., Holland, J. B., Lauter, N., ... Wisser, R. J.
complete list of authors
Teixeira, JEC||Weldekidan, T||de Leon, N||Flint-Garcia, S||Holland, JB||Lauter, N||Murray, SC||Xu, W||Hessel, DA||Kleintop, AE||Hawk, JA||Hallauer, A||Wisser, RJ