|Mahaffee, Walter - Walt|
Submitted to: Phytopathology
Publication Type: Abstract Only
Publication Acceptance Date: 6/1/2005
Publication Date: 8/1/2005
Citation: Peetz, A.B., Mahaffee, W.F., Jackson, J., Grove, G.G., Galloway, H. 2005. Rapid detection and quantification of airborne hop powdery mildew inoculum. Phytopathology. 95:S81.
Technical Abstract: Hop powdery mildew, Podosphaera macularis, causes severe economic losses of Humulus lupulus. Infection frequency is significantly reduced when diurnal temperature fluctuations have short durations of supra-conducive temperatures. This reduction is likely due to reduced sporulation or spore viability. Knowledge of aerial inoculum presence and density could help reduce pesticide applications particularly if they can be related to weather parameters that can be accurately forecasted. Primers for P. macularis were developed to the internal transcribed spacer region of ribosomal DNA from 42 isolates collected from Idaho, Oregon, Washington, and Europe. The PCR products were sequenced and compared with all BLAST data available for other Erysiphales, powdery mildews. Primers suitable for conventional PCR were developed and were specific for P. macularis of hops when tested against 45 closely related Erysiphales. Detection of P. macularis has been possible using conventional and qPCR following extraction of DNA from conidia impinged on silicon grease coated glass rods affixed to a Rotorod air sampler. Detection limits with qPCR were >100 spores. Detection and quantification of aerial inoculum presence will help base hop powdery mildew management programs on the presence of inoculum at any stage of the epidemic instead of assuming its presence.