Phenotypic characterization of southeastern United States open-pollinated maize landraces

Maize is the most important crop in the United States, but food production
and niche uses such as distilling often rely on varieties that are not
bred explicitly for these purposes. Farmers targeting niche food grain
markets have expressed interest in historical open-pollinated varieties of
maize, but few such populations are widely available, and even fewer are
well-characterized. We planted field trials of a subset of 76
open-pollinated heirloom varieties available from catalogs and the USDA
germplasm collection along with four F1 hybrid cultivars. We measured 24
traits across three years and three locations to characterize the selected
varieties and measure their phenotypic relationships. We identified a
subset of 19 traits useful for phenotypic analysis. Our results
demonstrate that many historical accessions contain substantial genetic
variation that should permit improvement from within-population selection.
Variety name and origin are often not useful indicators of phenotypic
relationships or potential crop value. Cluster analysis identifies nine
morphologically distinct groups within the varieties tested, which are not
fully in agreement with currently accepted landrace groupings, suggesting
a need for genetic analysis of larger samples of USA open-pollinated
populations to better define the natural classification of maize
indigenous to the United States.