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Gewählte Doctoral Thesis:

Markus Redl (2021): Effect of environmental conditions on the primary inoculum source of grapevine powdery mildew.
Doctoral Thesis - Institut für Pflanzenschutz, BOKU-Universität für Bodenkultur, pp 50. UB BOKU obvsg

Data Source: ZID Abstracts
The fungus Erysiphe necator causes powdery mildew of grape. The primary inoculum source plays a major role regarding disease pressure. The objectives of this study were to investigate the influence of environmental conditions on the survival of chasmothecia during overwintering, the physiological maturation of chasmothecia and the ascospore release from chasmothecia. The viability of ascospores in chasmothecia after overwintering was studied on grape leaf litter and bark samples. Furthermore, chasmothecia were subjected to natural overwintering conditions and subsequently the time of the first potential ascospore release was examined under optimal conditions in the laboratory. Additionally, weather factors affecting the actual ascospore release in the vineyard were studied. Noticeable differences in the densities of chasmothecia and the viability of ascospores between both years of the study and all examined vineyards were determined, whereas the differences in the average mean temperature between the vineyards from the period of formation of chasmothecia until bud break were low. Although high quantities of chasmothecia were found on leaf litter, the viability of ascospores was low. In contrast, a smaller amount of chasmothecia was detected on the exfoliating bark, but they had more viable ascospores. In the first overwintering season, the potential ascospore release started not until March; in the second season, it could be detected as early as fall. Temperature sums after chasmothecia formation related with the time of first potential chasmothecia dehiscence revealed that more than 480 degree days (base 8 °C) are necessary to reach the physiological maturity of chasmothecia. Precipitation and leaf wetness showed a significant positive correlation with ascospore release in the vineyard. The results of this thesis contribute to a better knowledge about the relation of weather conditions and epidemiology of grape powdery mildew.

Betreuer: Steinkellner Siegrid
1. Berater: Koschier Elisabeth Helene
2. Berater: Hage-Ahmed Karin

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