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POSTERS: Abiotic interactions

Requirements for in vitro pseudothecia development and ascospore maturation of Venturia effusa
Carolyn Young - Noble Research Institute, LLC. Debbie Boykin- USDA-ARS-SEA, Clive Bock- USDA ARS, Southeastern Fruit and Tree Nut Research Laboratory, Nikki Charlton- Noble Research Institute, LLC

Pecan scab, caused by Venturia effusa, is considered the most destructive disease of pecan in the southeastern United States. Current control practices require the use of fungicide sprays targeted at the asexual cycle addressing the polycyclic nature of this pathogen. However, identification and characterization of mating type idiomorphs led to successful crosses producing pseudothecia in vitro, suggesting the sexual stage may play a role in disease development. To investigate factors influencing the development of pseudothecia, three isolates of each mating type were crossed pairwise on oatmeal agar (totaling eight crosses). To assess pseudothecial production and maturation, the crosses were exposed to different temperatures (4, 8, 12, 16, 22C), incubation periods (2, 3, 4 mo), and photoperiods (0, 12h) at 24C following incubation. The number of pseudothecia were quantified, and their maturation assessed under the different environmental conditions. There were significant effects of temperature, month, and cross on production of pseudothecia. Although pseudothecia developed at all temperatures, greatest numbers developed at ?10C. Pseudothecia remained immature at 22C suggesting a cold period is required for ascospore maturation. The results indicate the likely environmental conditions to identify pseudothecia in the field, and potential times for ascospore release.