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Hallauer’s Tusón: a decade of selection for tropical-to-temperate phenological adaptation in maize

Author:
Teixeira, J. E. C., Weldekidan, T., de Leon, N., Flint-Garcia, S., Holland, J. B., Lauter, N., Murray, S. C., Xu, W., Hessel, D. A., Kleintop, A. E., Hawk, J. A., Hallauer, A., Wisser, R. J.
Source:
Heredity 2015 v.114 no.2 pp. 229-240
ISSN:
0018-067X
Subject:
Zea mays, abnormal development, artificial selection, corn, corn ears, crops, flowering, genotype-environment interaction, germplasm, latitude, phenology, phenotypic variation, photoperiod, plant adaptation, plant breeding, selection response, temperate zones, temperature, tropics, Iowa
Abstract:
Crop species exhibit an astounding capacity for environmental adaptation, but genetic bottlenecks resulting from intense selection for adaptation as well as 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 ten recurrent generations of 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. This study reveals the capacity for an all-tropical maize population to become adapted to a temperate environment in dramatic fashion: on average, families from generation 10 (g10) flowered 20 days earlier than families in generation 0 (g0), with a nine day separation between the latest g10 family and the earliest g0 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, a maladaptive syndrome including symptoms of excessive ear and plant heights correlated with later flowering observed in the original population was dramatically reduced in frequency by selection on flowering time.