Performance of maize (Zea mays) parental lines under low temperature conditions during winter season

To assess the effect of low temperatures on their vegetative growth, flowering behaviour and seed yield, a study was conducted at New Delhi, during the winter seasons of 1996-97 and 1997-98 with parental lines of 5 popular commercial hybrids, viz 'Ganga 5' [('CM 202' x 'CM 111') x ('CM 500')], 'Ganga 11' [('CM 202' x 'CM 111') x ('CM 501')], 'Ganga Safed 2' [('CM 400' x 'CM 300') x ('CM 600')], 'PHM 1'('CM 135' x 'CM 136') and 'PHM 2'('CM 137' x 'CM 138'). Low temperature regimes prevalent during December-February, retarded early vegetative growth (plant height), altered plant type (thickened stem and reduced internodal length) and caused various physiological damages on plant parts especially leaves (chlorosis, chlorotic bands, burning and drying). Large variability was observed among genotypes for chlorosis followed by chlorotic bands and yellowing of leaves. The low temperature injury was greater in first year when compared with second year, as the temperature was lower in the latter. All the genotypes showed varying degree of injuries but recovered by producing new flush of leaves in the second fortnight of February with onset of optimum temperatures (minimum temperature above 10 degrees C). The temperate line of maize 'CM 202' showed better tolerance when compared with tropical lines of maize ('CM 500' and 'CM 501', 'CM 111') which showed severe yellowing and drying of leaves. Open pollinated maize varieties, 'CM 500' and 'CM 501' were the most susceptible and exhibited severe yellowing and drying of leaves followed by 'CM I I V, 'CM 138', 'CM 136', 'CM 137' and 'CM 135' (chlorotic leaves with less drying) and 'CM 300', 'CM 400', and 'CM 600' exhibited poor growth and yellowing of leaves. Inbred line,'CM 202' showed mild yellowing with purpling of leaves. Single crosses' CM 400' x 'CM 300' and 'CM 202' x 'CM 111' were the least susceptible among genotypes and exhibited better growth, least yellowing and drying of leaves. The low temperature had marginal effect on final plant height, leaves/plant, seed yield and 100-seed weight but greater effect on Anthesis silking interval (ASI), days to flowering and its duration.