Pseudomonas syringae van Hall was recovered from 31 of 32 samples of red raspberry tissue showing typical symptoms of bacterial blight. Of the 99 isolates recovered, 85 were physiologically-typical, P. syringae isolates, three did not produce the fluorescent pigment, six did not utilize lactate and five did not produce toxin as determined by the Geotrichum candidum bioassay. When a suspension of 10⁷ CFU/ml was sprayed on the leaves of 6-week-old raspberry plants, 42 of 48 isolates caused necrosis within 4 days. No other bacterium recovered from the diseased raspberry tissue was pathogenic to raspberry in greenhouse tests. P. syringae isolates remained viable and retained their toxin-producing ability when stored for one year on nutrient glycerol agar at 5°C. Identical isolates stored on nutrient agar at 5°C or in sterile distilled water at room temperature either did not survive or lost their toxin-producing ability. There seemed to be a relationship between toxin-producing ability and an isolate's virulence as about 50% of toxin-producing isolates were rated pathogenic and 35% weakly pathogenic while none of the non-toxin-producing isolates were rated pathogenic and 60% were rated weakly pathogenic. A scheme was devised for rapid identification of P. syringae from raspberry tissue. An isolate was determined to be P. syringae if it produced a distinctive raised mucoid colony on nutrient sucrose agar, produced a fluorescent pigment, was oxidase negative and reacted in drop agglutination tests with an antiserum prepared against syringae. These tests could be done within three days. This scheme was used to study the overwintering site of P. syringae on raspberry. P. syringae was found to naturally populate 25-75% of raspberry buds during the winter months. Populations of 10⁴ CFU/six bud sample were most common in the buds that contained P. syringae. During the spring and summer months, P. syringae survived as an epiphyte on raspberry leaves both in the field and in the greenhouse trials. P. syringae was also shown to cause brownish-red spots surrounded by yellow halos on the leaves of raspberry during the summer months. About 90% of the P. syringae isolates from raspberry were ice nucleation active. Raspberry plants that had been sprayed with a suspension of 10⁷ CFU/ml and then held at -2°C for 4 hours developed symptoms similar to those of bacterial blight within 12 hours of the freeze treatment. In preliminary tests, raspberry cultivars showed varying degrees of resistance to P. syringae infection. Raspberry cultivar Chilcotin showed greatest resistance and cultivar Mailing Leo showed greatest susceptibility to Pseudomonas syringae infection. Three different species of bacteria were found in the normal microflora of the raspberry that were antagonistic to P. syringae in vitro. / Land and Food Systems, Faculty of / Graduate

Raspberry bushy dwarf virus (RBDV) is the sole member of the idaeovirus genus of plant viruses. It is a pollen-borne virus that economically impacts both red and black raspberries worldwide. Three strains of the bipartite RBDV have been reported. The common strain found in North America, South America, Australia, New Zealand and Europe and the resistance breaking strain found only in Europe are serologically indistinguishable while the black raspberry strain from North America is distinct. Resistance to RBDV is conferred by a single dominant gene, Bu. The resistance breaking strain is able to infect all raspberry cultivars containing the Bu loci. The sequence of a full-length clone of the common strain was determined and compared to the previously published sequence of the resistance breaking strain. Nucleotide homology between the two isolates was 97.6% for RNA 1 and 97.6% for RNA 2. Comparison of the predicted RNA 1 protein product of the two strains showed 97.9% homology. The predicted amino acid sequence of the movement protein and the coat protein from RNA 2 demonstrated 98.6% and 98.5% identity respectively. The differential rate of virus spread under field conditions in the Pacific Northwest was also investigated. The possibility of higher temperatures inhibiting virus infected pollen was explored by using in vitro germination and enzymatic staining procedures. Results from a two year study of virus-infected and virus-free raspberry pollen viability from both the Oregon and southern Washington region and the northern Washington and southern British Columbia region suggest temperature does not affect pollen germination or viability. Further studies were conducted to determine if a virus-degrading agent could be present on bee-stored raspberry pollen that becomes active only at higher temperatures. RBDV infected pollen from hives in northern Washington was collected and tested by ELISA after receiving either no heating or 32 hours of heating at 20, 30 or 40 C. Preliminary results indicate no such agent exists in red raspberry pollen from hives in the Pacific Northwest. / Graduation date: 2000

The effects of fenamiphos on soil and root populations of Pratylenchus penetrans were evaluated in four red raspberry cv. Willamette fields in Northwestern Oregon. Field 1 was a silty clay loam with 53% organic matter (OM). Field 2 and 3 were silty loam soils with 3.25 and 2.55% OM, respectively and field 4 was a silty clay with 7.1% OM. The nematicide, fenamiphos (10 kg a.i./ha) was applied in broadcast or band treatments on November 15, 1989. Additional plots in field 3, received a band-nematicide treatment on December 28, 1989 to evaluate the effect of application date on the control of P. penetrans in red raspberry. Field 4 had plots in sites with and without grass and weed ground cover in the aisles between raspberry rows to examine effects of ground cover on nematicide efficacy. Nematodes from soil and roots were sampled monthly from all plots in each field from October 1989 to October 1990. Soil populations of P. penetrans sampled within rows decreased between the October and December sampling dates in all four fields. Soil populations in 3 fields increased in density during mid-summer and reached their highest peak in the middle of September. A similar pattern occurred in P. penetrans soil populations from plots with or without ground cover in aisles between rows of raspberry in field 4. However, in this field, numbers increased in July and reached their peak density in August. Root populations of P. penetrans from red raspberry reached their highest number during spring and summer at all fields. No significant (P>0.05) differences in effectiveness of fenamiphos were detected between band and broadcast method of application and, also between the 2 application dates. Seasonal mean densities of soil populations from band application was only significantly lower than in nontreated controls in areas with ground cover in field 4, respectively. High variability in the numbers of P. penetrans in soil and roots of raspberry was observed throughout the year. Therefore, conclusions about the effectiveness of fenamiphos were difficult to assess. The efficiency of Baermann funnels was 43.9%, when a known number of P. penetrans was added to soil. Total yields of P. penetrans extracted from raspberry roots by mist chamber root extraction (MCRE) were higher (P = 0.05) than yields extracted by polyethylene plastic bag root incubation (PBRI). Approximately 90% of the total P. penetrans recovered was achieved after three and seven days of extraction for PBRI and MCRE, respectively. However, the extraction efficiency of MCRE was 30% higher than PBRI and the daily recovery lasted 28 and 18 days, respectively. / Graduation date: 1992

Graduation date: 1995

No description available.

No description available.

The objective of this study was to characterize an unknown agent associated with decline in black raspberry (Rubus occidentalis) in Oregon. A virus was found consistently associated with decline symptoms of black raspberries and was named Black raspberry decline associated virus (BRDaV). Double stranded RNA extraction from BRDaV-infected black raspberry revealed the presence of two bands of approximately 8.5 and 7 kilobase pairs, which were cloned and sequenced. The complete nucleotide sequences of RNA 1 and RNA 2 are 7581 nt and 6364 nt, respectively, excluding the 3' poly(A) tails. The genome structure was identical to that of Strawberry mottle virus (SMoV), with the putative polyproteins being less than 50% identical to that of SMoV and other related sequenced viruses. The final 189 amino acids of the RNA-dependent- RNA-polymerase (RdRp) reveal an unusual indel with homology to AlkB-like protein domains, suggesting a role in repair of alkylation damage. This is the first report of a virus outside the Flexiviridae and ampeloviruses of the Closteroviridae to contain these domains. An RT-PCR test was designed for the detection of BRDaV from Rubus tissue. BRDaV is vectored non-persistently by the large raspberry aphid Amphorophora agathonica, the green peach aphid Myzus persicae, and likely nonspecifically by other aphid species. Phylogenetic analysis of conserved motifs of the RdRp, helicase, and protease regions indicate that BRDaV belongs to the Sadwavirus genus. To assess the rate of spread BRDaV, four newly planted fields of black raspberries (Rubus occidentalis) in Oregon were studied for three years. In an effort to characterize the suspected complexity of synergistic interactions between BRDaV and other Rubus-infecting viruses, the prevalence of ten additional Rubus viruses was also monitored in the study fields. The timing of BRDaV infection as it relates to aphid populations and flights was also determined. Testing of nearby vegetation identified several symptomless Rubus hosts of BRDaV, as well as detection in multiple cultivars of black raspberry and several non-Rubus weeds. It was determined that BRDaV spreads rapidly with a low aphid threshold and consistently is associated with decline of black raspberries in Oregon. / Graduation date: 2006