Corn Evaluation for Early Season Planting System By Morphological Traits.

Early corn (Zea mays L.) planting is a strategy to avoid excessive heat and drought that often negatively influence grain production during its reproductive phase. We hypothesize that corn hybrids vary in their response to low temperatures, particularly root traits. The objectives of this study were to evaluate 33 corn hybrids with diverse genetic backgrounds and adapted to US Midsouth production system for cold temperature tolerance. Experiments were conducted by imposing very low, (21/13°C), low (25/17°C), and optimum (29/21°C), during seed germination and seedling under optimum moisture and nutrient conditions. Plant height, leaf area and number of leaves were assessed for plants growth those temperatures for 18 days. Several root morphological traits were assessed using winRHIZO system. Corn hybrids vary significantly for many traits measured, particularly plant component weight and root morphological parameters. Principle component analysis (PCA), a multivariate technique that allows reducing large number of observed traits in to a smaller set of traits that have the maximum contribution in separating the hybrids and total low temperature response index (TLTRI) methods which provides equal score based on their intensity, were used to categorize corn hybrid tolerance to cold temperature and used to group corn hybrids as cold-tolerant, moderately cold-tolerant, moderate cold-sensitive, and cold-sensitive. The PCA identified total, leaf and root weights, and root cumulative length, and length per unit volume as the most important morphological traits in describing hybrid tolerance to cold temperature. Based on TLTRI method, relative scores were provided for each hybrid which ranged from 22.45 to 29.52 among the hybrids.  The hybrids CR_8410, DY_51, and REV_43 were classified as cold sensitive, and AR_1262, DE_66, DE_68, and MY_707 as cold tolerant based on PCA and TLTRI techniques. Based on the relative scores assigned in this study and their yield potential in the respective environment, the corn producer could select hybrids that best suits his needs to maximize corn production during early production system.