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
Ml. Desprezloustau et F. Dupuis, 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, Annales des Sciences Forestieres, 51(6), 1994, pp. 553-568
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.