Sensitivity of maize hybrids to chilling and their combining abilities at two developmental stages

Maize (Zea mays L.), one of the most economically important plants grown in North America, is often subjected to cool conditions soon after sowing which can disrupt development. No studies on chilling sensitivity of maize at both germination and early growth developmental stages have been reported. To discern differences in chilling sensitivity between the germination and early growth phases, twelve hybrids originating from a complete diallel of four inbreds which differed in their sensitivity to chilling were subjected to laboratory screening tests at both these stages. Corresponding field trials were sown and parameters reflecting those evaluated in the laboratory were assessed. Estimates of general combining abilities and specific combining abilities were performed. Some lines that were initially chilling sensitive or tolerant at the germination stage altered their sensitivity to chilling at the early growth stage. This suggests that it is only possible to accurately evaluate chilling tolerance of maize by examining plants at both the germination-emergence and early growth stages as these two stages may be under the control of different genetic factors. Furthermore, based on the physiological growth parameters assessed both in the laboratory and in the field, it is not possible to reliably predict hybrid maize cold tolerance from knowledge of the inbreds' responses