L. Willocquet et al., EFFECTS OF RADIATION, ESPECIALLY ULTRAVIOLET-B, ON CONIDIAL GERMINATION AND MYCELIAL GROWTH OF GRAPE POWDERY MILDEW, European journal of plant pathology, 102(5), 1996, pp. 441-449
Conidia of Uncinula necator inoculated on vine leaf disks were exposed
to different irradiation conditions during various combinations of ir
radiation periods. In controlled experiments at constant leaf temperat
ure spore germination and mycelial growth were negatively affected by
the UV B doses, irrespective of the exposition duration. In semi-contr
olled condition experiments, conidia were exposed to shaded, sunny and
sunny without UV B radiation conditions. Shaded conditions were alway
s more favourable to spore germination and mycelial growth than sunny
conditions. Under two different ranges of temperature (20-24 and 26-31
degrees C for shaded conditions), the effect of radiation on germinat
ion and mycelial growth differed. Thus, the effect of radiation on spo
re germination and mycelial growth seems to be affected by temperature
. In general, radiation effects increased as the number of exposition
periods increased, indicating that both spore germination and mycelial
growth were reduced, but not totally stopped by the different exposur
es. Germination was most affected by exposures applied just after inoc
ulation, whereas mycelial growth was most affected by exposures applie
d one day after inoculation. These results indicate that radiation is
an important factor to consider for a better understanding of the rela
tionships between climate and grape powdery mildew epidemics.