Brief Summary of Minutes of Annual Meeting

Accomplishments 2010 W-2147 Objective 1. To identify and characterize new biological agents, naturally suppressive soils, cultural practices, and organic amendments that provide control of diseases caused by soilborne plant pathogens. CA. We examined a new peach replant disease soil and identified one stramenopile phylotype that negatively correlated with peach plant weights. This organism was Pythium vexans. CA. We examined a putative causal agent (Pythium ultimum) of peach replant disease using pathogenicity tests. Results were variable, as one trial showed lower plant weights with the agent while the other showed high levels of variation within treatments. These experiments are being repeated. CA- In previously reported research, we identified key microorganisms that suppress the population of a sugar beet cyst nematode (Heterodera schachtii) in a field site on the UCR Agricultural Operations. A model system was developed with the host/pathogen combination Arabidopsis thaliana and H. schachtii to evaluate the ability of D. oviparasitica to suppress cyst nematode reproduction under gnotobiotic conditions. The fungus reduced the average number of females developing on A. thaliana seedlings by close to 80%. No viable eggs developed in parasitized females. All infected females were eventually killed by the fungus. The fungus was never observed within the root, and consequently, cyst nematodes did not become infected until they broke through the root surface and were exposed to the rhizosphere. CA- In another project, a population of M. incognita was found to be suppressed by biological factors. Three genetically different strains of the fungus Pochonia chlamydosporia were isolated from parasitized root-knot nematodes. CA- To assess the efficacy of a zoosporic hyperparasitic species of Pythium (i.e., P. periplocum) in the control of two pathogenic species of Pythium (i.e., P. aphanidermatum and P. myriotylum). All three species have inflated sporangia. However, the hyperparasite can be distinguished from the plant pathogenic species base on the presence of spines on the oogonial walls. All three species are ecologically similar in their temperature requirements for vegetative growth and all three species produce zoospores, putting them on equal footing with respect to motility. The working hypothesis is that the hyperparasites, via zoospores, will follow the pathogen into infected root tissue and, via parasitism of the hyphae of the pathogen, inhibit reproduction and growth of the pathogen. Results- Pythium periplocum colonized cucumber roots infected by pathogenic zoosporic Pythium species, but the rapidity of colonization by the hyperparasite was not fast enough to prevent or reduce disease severity caused by the plant pathogenic species. Oospores of both the pathogen and hyperparasite were observed in colonized root tissue. CA- To evaluate the efficacy of sodium salicylate in the management of subclinical and clinical zoosporic pathogens of hydroponically-grown lettuce. Results- Sodium salicylate at 1, 10, 25, 50 and 100 ug /ml in the recirculating nutrient solution did not provide control of root disease caused by either Pythium dissotocum ( a subclinical root-infecting pathogen) or Phytophthora drechsleri ( a clinical root-infecting pathogen) of hydroponically-grown lettuce. Additionally, the chemical, at all concentrations except 1 and 10 ug/ml, were phytotoxic. Other chemical treatments (Revus and Presidio, at 1, 0.5 and 0.1 ug a.i./ml) were efficacious in management of root rot caused by these two pathogens. CA- To assess the role of Olpidium bornovanus in vine-decline of melons in the field and evaluate the efficacy of surfactants in control of root rot caused by Olpidium bornovanus. Field trials were conducted (in collaboration with Dr. Donna Henderson) at the Desert Research and Extension Center in Holtville, Ca. The field plot was naturally infested with both M. cannonballus and Olpidium bornovanus. Chemical treatments (which were applied at periodic intervals over the growing season via the drip irrigation system) included the following: Agral 90 (a non-ionic surfactant), and two fungicides: Cannonball and Quadris. Melons were sown on March 17th and the crop was harvested on June 23rd. Root rot severity ratings indicated that the surfactant treatment was not significantly different that the non-treated control. Root rot severity was significantly lower in the Cannonball and Quadris treatments compared to the control and Quadris was superior to Cannonball. CA. To identify the microbe involved in the induction of germination of Monosporascus cannonballus ascospores. Monosporascus cannonballus, a host-specific root-infecting ascomycete, is the causal agent of a destructive disease of melons known as vine-decline. Ascospores, which function as the sole survival propagules and primary inoculum for this soilborne fungus, germinate only in the rhizosphere of melons growing in field soil. However, no ascospore germination occurs in the rhizosphere of melons if the field soil is heated to temperatures greater that 50°C prior to infestation with ascospores. This observation suggests (i) that germination is mediated by one or more heat-sensitive members of the soil microflora and (ii) that melon root exudates alone are not the germination stimulant. Results: Although bacteria or actinomycetes were heretofore suspected as the germination-inducing microbe(s), our recent data demonstrate that the culprit is an obligate, holocarpic, root-infecting zoosporic fungus known as Olpidium bornovanus. Ascospore germination in sterile field soil occurred only in the rhizosphere of melon roots that were colonized by a host-specific melon strain of O. bornovanus. MI- Characterization of disease suppressive soil against potato common scab. We have successfully used pyroseqeuencing, bioinformatic and computational methods in a small-scale pilot study with limited samples to study rhizosphere-associated soil microbes from the PCS 'conducive' and 'suppressive' soil. The total operational bacterial taxa from both disease conducive and disease suppressive soil differ both in total numbers and shared number of taxa. The diversity of bacterial Phyla, Classes, Orders, Families and Genera found in the conducive and suppressive soil samples was 20, 49, 87, 173 and 335 respectively. The number of bacterial taxa in disease conducive and suppressive soils was 565, 859, respectively. 26.69% of bacterial taxa are shared by the two types of soils. MI- Diversity of pathogens that cause potato common scab. Sequence comparison indicated multiple species from the same tuber, between fields in proximity, and in the same county. Three isolates from tubers collected from Monroe County showed sequence similarity to Streptomyces stelliscabiei, the first confirmed report in MI. However, isolates from other potato fields from the same county could only be identified to Streptomyces spp. One isolate lacked nec1 and one isolate lacked tomA. All isolates in this study were txtAB positive based on PCR analysis. OH- Marker-assisted recovery and characterization of novel biocontrol bacteria. We initiated a multifactor screen to quantify the effects of different factors structuring plant-associated bacterial populations. Three collections were developped, each containing over 1000 isolates. Genotyping of these collections using amplified rDNA restriction analysis revealed between 62 and 132 genotypes in each. From these over 400 isolates were selected to determine the degree of fine-level diversity present. Chi-squared analyses of the genotype data revealed that certain factors had a greater impact on the recovery of novel genotypes, and that simple changes in in situ and ex situ sampling protocols could be used to recover different species of bacteria. High through put phenotyping of these strains is underway, but preliminary indications are that over a dozen isolates, some of them belonging to novel species, were obtained with efficacy equal to or greater than an organically-acceptable commercial biopesticide standard. OR. Ten horticultural nurseries were investigated for the frequency of Phytophthora contamination in each of three Critical Control Points in the production process: used containers, irrigation water, and gravel underlying container yards. Five of the nurseries were participants in a nursery certification program, the Grower-Assisted Inspection Program (GAIP), sponsored by the Oregon Dept. of Agriculture, and five nurseries were not (non-GAIP). The frequency of contamination was determined by baiting of soil and water samples collected in fall and spring. Overall, there were no significant differences in the frequency of contamination between GAIP and non-GAIP nurseries. The timing of water sampling appears to be very important, with significantly greater recovery of Phytophthora in fall as compared to spring. Used pots and gravel were a source of Phytophthora in several nurseries, and irrigation water was contaminated in most nurseries that did not treat their water, including two of the GAIP nurseries. Several of the nurseries adopted best management practices to curtail their Phytophthora contamination problems as a result of our study. Because of our findings, the Oregon Dept. of Agriculture will require that nurseries participating in GAIP must disinfest recycled irrigation water. WA-Cereal cyst nematodes have become established in Eastern Washington, and may significantly reduce yields. Waitea circinata (Rhizoctonia oryzae) has been isolated from most cereal production areas in the U.S., but its pathogenicity is unknown. WA-Rhizoctonia solani AG8 appears to be the predominant AG associated with stunting in onion bulb crops following winter cereal cover crops. WA-Pythium irregulare Group I, P. ultimum, P. torulosum, P. adhaerens, P. middletonii, P. dissotocum, P. abappresorium and P. violae are amongst the most common Pythium species found in certified organic fields in the irrigated region of the Columbia Basin of central WA. Objective 2 To understand how microbial populations and their gene expression are regulated by the biological (plants and microbes) and physical environment and how they influence disease. MS. Our project, "Transcriptomic Dissection of the Interaction Between Oryza sativa and Burkholderia glumae" started in Jan. 2011 and will end in Dec. 2011. We are working to accomplish our objectives. OH. Towards the discovery of a new genes involved in biological control. In collaboration with Korean researchers, the genome sequence for Chromobacterium strain C61 was determined. The strain was found to harbor a disproportionate number of chitinase genes as well as a novel NRPS gene. Random and site directed mutagenesis have been used to reduce biocontrol activity of this strain, in order to determine which products might be involved in disease suppression. WA-Microbial communities within a Rhizoctonia diseased area in a field are different from the surrounding areas, both qualitatively and quantitatively. These communities may be responsible for long-term suppression of Rhizoctonia disease under no-till conditions. Objective 3. To implement sustainable management strategies for soilborne pathogens that are biologically based and compatible with soil health management practices. MI. Effect of chestnut extract/tissue in inhibiting soilborne plant pathogens. Extracts from chestnut leaves, shells, and pellicles were all inhibitory to various microorganisms. Bacteria were more sensitive than fungi to the extract. Effective concentration for 50% growth inhibition (EC50) varied, depending on the microorganisms tested. Of the tested microorganisms, Pseudomonas fluorescens was the most sensitive (EC50 = 4.4 ug/uL), and Phytophthora cambivora was one of the least inhibited (EC50 = 185 ug/uL). Extracts of the chestnut type 'Colossal' showed a greater inhibition than those of Chinese. High temperature did not affect the inhibitory effect. Pellicle and shell extracts reduced disease caused by Streptomyces scabies in the greenhouse. The active compounds were identified as tannins and flavanoids. MI. Effect of Bacillus sp. BAC03 on Streptomyces scabies. In the greenhouse, Bacillus sp. strain BAC03 significantly reduced scab symptoms in radish. BAC03 also increased the biomass of radish by 40% compared to the non-treated pots, both of which were infested with S. scabies. MI. Effect of essential oil in inhibiting Phytophthora capsici. Among the 14 essential oil tested, red thyme, oregano, and palmarosa exhibited high antifungal activity against Phytophthora capsici and Streptomyces scabies with both contact and volatile mode. With P. capsici isolate 12899, the EC50 of red thyme, oregano, and palmarosa is 0.06, 0.08, and 0.04 mg/L by direct contact, and 0.08, 0.08 and 0.04 by using volatiles. None of the oils showed inhibition against Sclerotinia sclerotiorum. Essential oils, red thyme, oregano, and palmarosa had a significant inhibitory effect on sporangium, zoospore and oospore production. These oils also exhibited a potential to inhibit germination of spores. NM. A greenhouse study was conducted to determine the effects of transplant and soil treatment with biofungicides on the development of Phytophthora blight on chile pepper. Transplants were immersed in 0.1% suspension of two biofungicides (Actinovate and Mycostop Mix) and water (control) three days prior to transplanting. Soil was drenched with 0.1% Mycostop Mix, 0.1% Actinovate, Ridomil Gold EC (1.16 liter/ha), or water (control). Disease severity level was not significantly affected when transplants were treated with Actinovate and Mycostop Mix. The lowest disease severity was observed when soil was treated with Ridomil Gold EC. An effective soil treatment that reduces soil inoculum potential is essential in the management of P. capsici. NY- The replicated 9 cover crops (winter rye grain + hairy vetch, oat, sudex, forage radish, red clover, rapeseed, buckwheat, wheat, and a fallow/control) evaluation trial established in four production fields with different management histories (2 acres each) was continued in 2010 (a total of 108 plots). All plots were sampled for root and soil health assessments in May 2010, over-wintered cover crop incorporated and then all the plots were planted to snap bean cv. 'Caprice'. Bean yield was highest in the field with the highest soil health parameters and the lowest root rot severity ratings. The cover crops also greatly affected root health and yield of beans, but varied among the 4 fields. However, yield of beans was lowest and root rot severity ratings were highest with buckwheat as the cover crop. All the cover crops were re-established in the same plots for another cycle of evaluation. NY- In collaboration with the Cornell soil health team, the replicated trial on the combined effects of tillage (No-till, Zone-till, Plow-till), cover crop (Rye grain, Vetch, Fallow), and crop rotation (Vegetables vs. Grain/Forage/Vegetable) on soil and root health parameters was continued at the long-term soil health site at the Gates Farm, Geneva. In May 2010, the 72 plots were sampled for assessing root health and soil health prior to any tillage practices. Pickling cucumber was planted in the vegetable rotation (36 plots) and Sudan grass in the other rotation. In 2010, results of the greenhouse soil bioassay showed that root rot severity was significantly affected by crop rotation, only slightly by tillage systems and no measurable effect was observed among the 3 cover crop treatments. However, results accumulated to date suggest that reduce d tillage systems appear to improve the value of measured soil health indicators the most. OR- Commercial greenhouses have relied on chemical fumigants and drenches to control soilborne pathogens between cropping cycles, but increasing restrictions on the use of these materials is forcing growers to explore other ways to manage diseases. Parke investigated non-chemical alternatives to fumigation including removal and replacement of substrate, in situ pasteurization, solarization, and solarization followed by soil incorporation of the biocontrol agents SoilGard and RootShield. Solarization for 6 weeks during the summer was not adequate for killing inoculum of Thielaviopsis basicola, Rhizoctonia solani, or Pythium irregulare buried 4" beneath the soil surface, but solarization did reduce damping-off disease in soil bioassays. SoilGard 12G appeared to give some improvement in root quality and plant health. Additional research is proposed to document the effectiveness of solarization and biocontrol amendments under controlled greenhouse conditions in Oregon. WA-Brassica seed meals may suppress pathogens involved in apple replant disease, which is significant given many fumigants (e.g., methyl bromide) can no longer be used. WA-Wheat varieties with aluminum tolerance can overcome the low yield problems in acid soils of wheat grown in rotation with bluegrass. WA-Limestone amendments can effectively suppress Fusarium wilt in spinach seed crops on acid soils, but the degree of suppression is influenced by susceptibility of the spinach parent lines. A soil bioassay can effectively identify the potential risk of spinach Fusarium wilt. WA-Fungicide seed treatments do not appear to manage stunting in onion bulb crops caused by Rhizoctonia, but increasing the duration between incorporating cereal cover crops and planting onion bulb crops appears to reduce the severity of stunting. WA-Soil fumigation exacerbates the rate of infestation of soil by Verticillium if an infected spinach seed lot is planted, but effective fungicide seed treatments can significantly reduce the rate of seed transmission. Objective 4. Provide outreach, education, extension and technology transfer to our clients and stakeholders- growers, biocontrol industry, graduate and undergraduate students, K-12 students and other scientists All- This group conducts outreach and extension to growers, outlined in the publication section under Extension Publications and Outreach. OH-Several presentations were made to organic growers related to the availability and efficacy of biopesticides. These were made to the Ohio Ecological Food and Farming Association's annual conference and posted online as part of both eOrganic and Ohioloine extesnion. OR- Parke presented her findings on the systems approach for managing Phytophthora diseases at a workshop for growers, at a nursery field day, in a state-wide nursery association seminar, and in an article published in a nursery trade journal (circulation 8,000). She also gave an invited presentation to fellow scientists at the Kanuga workshop on diseases and pests of ornamentals. The research on solarization and biocontrol was presented at a nursery field day. NY-An interactive train-the-trainer workshop on soil health issues was held during August 15 - 19, 2010 in collaboration with the Cornell Soil Health Team. Twenty-four participants from across the country and abroad attended the workshop, which consisted of a mix of classroom and laboratory and field hands-on experience with assessment protocols as well as farm visits. Also, over 25 growers, extension educators, and industry personnel attended a cover crop field day on October 19, 2010 to observed and discuss the establishment of diverse cover crops and their potential impact root and soil health parameters as well as yield parameters of the indexing main crop, snap beans. WA- Researchers at USDA-ARS in Pullman have developed outreach programs with elementary and high schools on the Colville Reservations, including monthly classes and a summer camp. They also sponsor summer internships and work with Bellevue Community College.