VARIATION IN THE PHENOLOGY OF SHOOT ELONGATION BETWEEN GEOGRAPHIC PROVENANCES OF MARITIME PINE (PINUS-PINASTER) - IMPLICATIONS FOR THE SYNCHRONY WITH THE PHENOLOGY OF THE TWISTING RUST FUNGUS, MELAMPSORA-PINITORQUA

The phenology of shoot elongation was monitored for 2 or 3 years at 4 sites in France with 6 maritime pine geographic provenances. Within ea ch provenance, the onset of phenological stages, especially the earlie r ones, was better predicted by heat sums than by calendar days. The a ccuracy of prediction could be increased by about 50% for the earliest studied stage (from 19 to 10 d). However, temporal and, to a greater extent, site effects were still observed for heat sums. These may be a ttributed in part to stressful environmental conditions for pine. The geographic provenances used represent a range of significantly differe nt heat requirements, the Tamjout (from Morocco) and the Leiria (from Portugal) provenances representing the earliest and the latest, respec tively, with a difference of approximately 100 degree-days (for a thre shold temperature of 0-degrees-C). A positive correlation was observed between precocity and vigour though this could not explain difference s in precocity between provenances. A comparison of pine and rust (Mel ampsora pinitorqua) phenologies, monitored at the same sites in south- west France, revealed that synchrony between the host-susceptible stag es and the parasite-spore-producing stages did not always occur. The e arliness of the Tamjout provenance pre-disposed it to greater rust inf ection than other provenances due to better synchrony with basidiospor e production. Variations in host-parasite synchrony are discussed from an evolutionary perspective and in relation to the prediction of infe ction risk.