Effects of Dehardening on Resistance to Freezing an Infection byTyphula ishikariensisin pratense

The resistance of seed-grown plants of Phleum pratense to freezing and to infection by Typhula ishikariensis was considerably enhanced after 2 weeks' exposure to hardening at +1°C. Dehardening of the plants at +12 to 18°C, for 1 or 2 weeks, reduced the freezing resistance significantly. The same treatment did not lead to any decrease in resistance to T. ishikariensis. These observations may indicate that low temperature hardening initiates different mechanisms for resistance to freezing and for resistance to a low temperature pathogen.