Selection for Cold Germination in Two Corn Populations 1

Tolerance of corn ( Zea mays L.) to low temperature conditions after planting requires rapid germination, vigorous seedling growth, and resistance to disease and insect pests. A selection scheme designed to improve cold tolerance in breeding material was initiated in two breeding populations, Iowa Stiff Stalk Synthetic (SSCG) and Pioneer Cold Tolerant Synthetic (CTCG). Laboratory and field selection were employed in the procedure. Seedlings developed from the first seeds to germinate at 7.2 C in the laboratory (20% selected) were transplanted to the field, selected for agronomic traits, and self‐pollinated. The selfed progenies were recombined in winter nurseries to initiate the next cycle of selection in the laboratory. Regression analyses of the four cycles of selection indicated that cold germination under laboratory conditions (7.2 C) improved 8.8 and 9.9% per cycle in CTCG and SSCG, respectively. In the field, however, little improvement was observed in emergence or seedling vigor. The lack of correlation between laboratory and field results for these cold‐tolerant traits was attributed to mild spring weather during the 2 years of evaluation. Selection for germination at cold temperatures did not have any detrimental effects on other agronomic traits measured in the populations.