RELATING GERMINATION DYNAMICS OF MELAMPSORA-PINITORQUA TELIOSPORES TOTEMPERATURE AND RAINFALL DURING OVERWINTERING

The influence of overwintering conditions on the dynamics of Melampsor a pinitorqua teliospore germination in spring was assessed in the Land es forest (south-western France), over 3 years. January accumulated te mperature was the variable most strongly linked to the date of optimum germinability (JDOG), in a negative direction. A linear regression us ing accumulated degree-days and number of rainy days in January accoun ted for nearly 70% of overall variation in JDOG. Accumulated temperatu re from October 1 and January 1 to the date of optimum germinability s howed lower coefficients of variation than JDOG. The best predictions of JDOG in an independent data set were obtained by using the accumula ted temperature from January 1 to the dare of optimum germinability or a linear regression based on accumulated temperature in January. The mean square root error of prediction was approximately 5 days. The eco logical significance of the temperature-dependent model is discussed i n relation to the synchronization of rust and pine phenologies.