Location: Horticultural Crops Research2011 Annual Report
1a. Objectives (from AD-416)
1) Validate a quantitative PCR (qPCR)-based assay for P. rubi evaluations from raspberry roots and soil. 2) Continue evaluations of solarization and Brassicacaceous seed meal amendments as preplant treatments for raspberry. 3) Establish trials to determine whether bed fumigation and alleyway management methods sufficiently delay pathogen entry into planting beds to permit successful plant establishment.
1b. Approach (from AD-416)
First, we will validate a quantitative molecular assay to improve our ability to evaluate treatment effects on P. rubi. The bioassay we currently use is very sensitive to small amounts of P. rubi but not distinguish moderately effective treatments from non-treated controls. A truly quantitative assay will give us a more realistic assessment of the efficacy of treatments. A quantitative real-time PCR (qPCR) assay for P. rubi is already in development in our lab. We verified that we can amplify and detect the correct region of P. rubi DNA, and propose to validate the test across multiple P. rubi isolates, and validate that it is accurate using DNA recovered from soil or raspberry roots. In preliminary experiments, we found that soils amended with Brassica juncea or Sinapis alba seed meal suppressed P. penetrans; Agrobacterium tumefasciens was also suppressed in B. juncea-amended soils. Solarization is another non-chemical pretreatment option, which has been shown to prevent root rot for 2-3 years in western Washington fields. Documents grant with Washington State University.
3. Progress Report
We are developing short and long-term alternatives to broadcast fumigation for raspberry growers. This includes including development of an improved PCR assay for Phytophthora rubi, the most common cause of raspberry root rot. This assay will ultimately help us evaluate the success of treatments in controlling P. rubi, and will help growers determine the need for fumigation or other preplant treatments. We conducted greenhouse and field evaluations of solarization and brassicaceous seed meals, determining that the combination of solarization and amendment with B. juncea seed meal substantially reduced P. rubi viability as well as root lesion nematode population densities. We established five grower trials comparing bed fumigation with broadcast fumigation, and have begun to evaluate the effectiveness of bed fumigation and alleyway management for disease, nematode and weed control. Methods of project monitoring included meetings, e-mail, and phone calls.