Evaluation of Maize Germplasm for Tolerance to Low Temperature Stress under Field and Laboratory Conditions

Sixty-four inbred lines of maize ( Zea mays L.) were evaluated for their tolerance to low temperature stress in three experiments at Punjab Agricultural University, Ludhiana. All the 64 inbred lines were evaluated under laboratory conditions. Forty-four of these were also studied under field conditions. In the laboratory test the materials were exposed for four hours to 1, 0, ?1, ?2, ?3 and ?3.5°C on six successive nights. Significant genotypic differences were observed for freezing injury in laboratory test and for frost and non-freezing (yellowing) injuries in field evaluation. Expression of frost injury under field condition and freezing injury in laboratory test at ?2, ?3 and ?3.5 °C showed positive correlation in one experiment. The range and mean square for freezing injury of inbred lines were the largest either at ?3 or at ?3.5°C. The correlation of yellowing with frost injury in field and freezing injury in laboratory at ?3 and 3.5°C was not significant suggesting the lack of association between yellowing and frost/freezing injury.