GROWTH RESPONSES OF EARLY MATURING INBRED LINES OF CORN TO SUBOPTIMAL TEMPERATURES

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Abstract
Considerable genetic variability was observed among 32 inbred lines of corn (Zea mays L.) for emergence percentage, emergence index (rate), and seedling dry weight when evaluated under controlled low temperature regimes. Emergence percentage ranged from 45 to 100%, emergence indices from 14.7 to 18.7 days, and seedling dry weights from 0.19 to 1.19 g/plant. Simple correlation coefficients indicated a significant (P = 0.05) and positive association between emergence percentage and emergence index (rate). Neither of the two emergence parameters were significantly associated with seedling dry weights. Twelve inbreds selected for field evaluation based upon their performance under controlled low temperature environments, expressed marked differences with respect to emergence percentage, seedling growth, time to silk, and grain yields. The two best inbred lines tested under both environments were CK76 and CO255. Although the emergence traits as determined under controlled environmental conditions were not significantly correlated with those evaluated in the field, measurements of post-emergence seedling growth were significantly and positively associated between the two environments. Thus the use of a predetermined optimal ambient temperature regime can be used as a screening method to identify strains with potential vigor and cold tolerance under field conditions.Key words: Corn, cold tolerance, physiology