Phenotypic variation in the phenology of ascospore production between European populations of oak powdery mildew | Variabilité phénotypique dans la phénologie de la production d’ascospores entre populations européennes d’oïdium du chêne
2009
Marçais, Benoit | Kavkova, Miloslava | Desprez-Loustau, Marie-Laure
• Oak powdery mildew severity (Erysiphe alphitoides) is usually mild in Europe because epidemics start late in spring, at the end of the first oak growth unit maturation. However, the disease can occasionally be very severe when strong infection occurs early during the development of the first growth unit, suggesting that host-pathogen synchrony in spring could be a critical factor in disease severity. • We studied the timing of ascospore production in a given environment for four E. alphitoides populations sampled from SW France to the Czech Republic to determine whether this trait shows variation within Europe. • Timing of ascospore production was clearly influenced by environmental factors as chasmothecia from a single origin showed very different dates of optimal ascospore production when transferred for overwintering in locations with different climate. In common garden experiments, no differences were observed between populations for the date of optimal ascospore production. • Results suggest little genetic differentiation for timing of ascospore production for E. alphitoides populations across Europe and therefore a lack of local adaptation to their host phenology. Availability in ascospore inoculum is limited during host budburst, explaining the low infection usually observed on the first oak growth unit.
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