USE OF INBRED SEEDLING COLD TOLERANCE TO PREDICT HYBRID COLD TOLERANCE IN MAIZE (ZEA-MAYS-L)

The ability of a corn genotype to emerge in the cold, and the development of hardier corn lines is important for reliable corn production in Southern Manitoba. The study sought to determine if inbred cold tolerance could be used to predict accurately hybrid cold tolerance. Eighteen single-cross maize (Zea mays L.) hybrids were formed by crossing the known cold-tolerant inbred CO255 to each of 18 inbred lines. Following germination, five seedlings of each inbred and hybrid were arranged in a five-replicate RCBD and grown in a growth cabinet maintained at 10-degrees-C. Weekly observations of colour and leaf viability, shoot growth, stage of development, and number of dead plants were averaged over the five replicates providing weekly mean values. By averaging weekly values over the 5-wk study, overall mean values were obtained upon which the genotypes were ranked for relative cold tolerance. Correlation coefficients between weakly measures and the final rankings suggested future estimates of cold tolerance could be accurately obtained from an initial observation at emergence, and one at seedling harvest, with only shoot length, leaf viability, leaf colour, and dead plants being noted. No maternal effects were found among six reciprocal crosses involving the common parent CO255. In the final evaluation of cold tolerance CO255 did impart cold tolerance to the respective hybrids, although no common pattern of inheritance was found for the hybrids studied. We concluded that inbred cold tolerance cannot be used to predict accurately hybrid cold tolerance.