Contribution of the hardening period to developping freezing resistance in durum wheat (Triticum durum Desf.)

In the present study, changes in freezing resistance during the hardening of nine durum wheat (Triticum durum Desf.) cultivars were evaluated in a phytotron in Martonvasar. Hardening was carried out at a constant temperature of +2 degrees C for 0, 10, 20, 30, 40, 50, 60, 70, 80, 90 or 100 days, after which the plants from all the treatments were frozen at -13.5 degrees C. Considerable varietal differences in the hardening kinetics were recorded for the durum genotypes investigated. The freezing resistance of the genotypes was negligible after 0-20 days of hardening. The maximum degree of freezing resistance was reached after 30-50 days of hardening. A considerable decrease in freezing resistance was observed in plants kept at +2 degrees C for 60 days or more. Judging by the results of these and earlier experiments, on average T. durum genotypes achieve a lower level of hardening, which generally has a shorter duration, than that observed in winter T, aestivum cultivars.