Corn Evaluation for Early Planting Production System By Physiological Traits.

Earlier planting to escape summer drought and high temperature has increased the importance of cold tolerance in corn (Zea mays L.). The objectives of this study were to assess cold tolerance among the corn hybrids more commonly grown in the US Mid-south using physiological and photosynthesis traits, and to classify hybrids into different groups of tolerance. Twenty one corn hybrids were subjected to three day/night temperature treatments, optimum (29/21°C), low (25/17°C), and very low (21/13°C) after seedling establishment [15 days after planting (DAP)]. Photosynthesis and growth and developmental parameters were assessed between 30 and 34 DAP. Corn hybrids significantly varied for the traits measured among the treatments and their relative responses compared to optimum conditions. A total low temperature response index (TLTRI) method was used to categorize corn hybrids to low temperature and to group corn hybrids as cold-tolerant, moderately cold-tolerant, moderately cold-sensitive, and cold-sensitive. Based on the TLTRI method, relative scores were provided for each hybrid, which ranged from 31.3 to 39.8. The hybrids AR1262 and P1636YHR were classified as cold-tolerant and H68B and ST11504VT3 as cold-sensitive. Quantified cold tolerance related traits identified in this study will be useful in corn breeding programs to develop hybrids tolerant to low temperatures. Based on relative scores developed in this study, corn producers could select to maximize corn production in an early planting production system.