2012 - Washington Red Raspberry Commission

methods are more recent (Bilodeau et al., 2012, Duressa et al., 2012, Markakis et al., 2009). For
the culture-based method, plant samples are surface-disinfested with a 10% bleach solution, cut
into segments, and then plated into petri dishes containing a semi-selective medium from which
diagnostic V. dahliae cultures will grow if the pathogen is present. Soil samples will be dried for
2 weeks to eliminate competing contaminant fungi and then spread on the same semi-selective
medium used above. For the DNA-based method, V. dahliae DNA will be extracted and
amplified from plants and soil samples using established protocols (Bilodeau et al., 2012,
Duressa et al., 2012, Markakis et al., 2009).
Pathogen incidence for each site (diseased and nondiseased) will be determined by the presence
or absence of V. dahliae as detected by each method. Quantification of the pathogen from plant
samples will be based on the number of plants from which the pathogen was detected by each
method. Quantification of the pathogen from soil will be based on the number of V. dahliae
cultures that grow from each soil sample or the amount of V. dahliae DNA amplified by the
DNA-based method. Data will be compiled and results from both diseased and nondiseased sites
will be compared to determine the incidence of V. dahliae in red raspberry production fields
(Objective 1). Results from plant and soil samples at diseased sites will be used to determine if
the presence of V. dahliae in the soil is associated with disease (Objective 2) and to determine
which inoculum levels are associated with disease symptoms (Objective 3). Finally, results from
each method will be compared to determine which method is best at detecting and at quantifying
V. dahliae from plant and soil samples (Objective 4). Incidence data will be analyzed using the
chi-square test for independence and quantity data will be analyzed using ANOVA.
Timeline:
Activity 2013 2014
Plant and soil sample collection June-October June-October
Plant and soil sample processing June-December June-December
Anticipated Benefits and Information Transfer:
This research will identify if V. dahliae is widely prevalent and causing disease in Washington
red raspberry production fields. It will also identify inoculum levels that are associated with
disease and identify appropriate methods for V. dahliae detection and quantification. Results will
lay the foundation for future research including disease screen assays for resistance among red
raspberry cultivars and the evaluation of production (e.g. fertilization, irrigation, etc.) and disease
management practices (fumigant rates, chemistries, etc.) for their effects on inoculum levels and
disease development. Findings will also help growers interpret results from diagnostic
laboratories. Our research results will be presented to red raspberry growers at meetings (Small
Fruit Conference, Lynden) and communicated to the Washington Red Raspberry Commission,
Peerbolt Crop Management, and Whatcom County Extension for inclusion in their newsletters.
107