ARS | Publication request: Effect of prior vegetative growth, inoculum density and light on conidiation in Erysiphe necator

Submitted to: International Workshop on Grapevine Downy and Powdery Mildew Proceedings
Publication Type: Proceedings
Publication Acceptance Date: September 20, 2010
Publication Date: November 1, 2010
Citation: Gadoury, D., Wakefield, L., Seem, B., Cadle Davidson, L.E., Dry, I. 2010. Effect of prior vegetative growth, inoculum density and light on conidiation in Erysiphe necator. International Workshop on Grapevine Downy and Powdery Mildew Proceedings. 51-53.

Technical Abstract: A driving force in epidemics of grape powdery mildew is the abundant production of conidia. Our objective was to better define the three factors involved in the qualitative change that occurs when a mildew colony switches from vegetative growth to sporulation –inoculum density, light, and a sporulation signal initiated at the colony center. Latent period decreased exponentially as the number of germinable conidia increased above 1 per sq mm until inoculation density reached approximately 10 to 20 germinable conidia per sq mm, above which only a slight decline in the duration of the latent period was observed. Light was necessary for initiation of sporulation. Colonies incubated in darkness were competent for sporulation, but required light to initiate the process. Finally, excision of the colony center at 4 days post inoculation (DPI) delayed sporulation in the remaining hyphae until 9 to 10 DPI. Colonies whose centers were excised at 5 DPI sporulated at 7 DPI, similar to nonexcised control colonies. Our improved biological knowledge of sporulation could lead to novel disease management strategies.