Brief Summary of Minutes of Annual Meeting

Brief Summary of Minutes of Annual Meeting Harald Scherm  Administrative Advisor oversaw the annual meeting and provided guidance and information on the renewal process. To date 20 members are signed up for the new S1053. As S1028 has come to a close a termination report will need to be prepared. When discussing future directions for the research group, emphasis on collaborative proposal development was suggested as an area the group could work together to improve on from the last project period. Those in attendance included: Sheng Yu - Mississippi State University Kurt Lamour  University of Tennessee Kirk Broders  University of New Hampshire Craig Rothrock  University of Arkansas Carla Garzon  Oklahoma State University Craig Canaday  University of Tennessee WTREC Louisa Santamaria  Oregon State University After introduction, each member in attendance provided a presentation and update of current ongoing research and results from the past year associated with the project. At the conclusion of the presentation, the group came to a consensus to hold next years meeting of the S1053 multi-state group in Oklahoma City, OK around the first week of November. Kurt Lamour was nominated for Secretary and a unanimous vote confirmed his new post. As secretary, Kurt is also the Chair-elect. Kirk Broders will be the incoming Chair, and Craig Rothrock is the outgoing chair. The final topic of discussion was how we can better integrate projects by individual investigators to tackle larger problems that require a multi-state effort to accomplish. Some of the idea but forth included: - Chloride and relationship to Pythium - P. capsici distribution and management - Pythium taxonomy and describing non-spore forming species - Disease complexes symposium/workshop - Rhizoctonia population resources - International Potato Center for Rhizoctonia resources Meeting adjourned.

Objective 1. Evaluate the population genetic diversity of soilborne pathogens and antagonistic microorganisms in different growing systems and regions using traditional and metagenomic approaches. In Mississippi, 900 bacterial isolates were obtained from soils and plant samples and tested for antimicrobial activities and discovery of novel antagonistic bacteria. Approximately 60 isolates showed significant antifungal activities in bioassays against Geotrichum candidum and more than 20 isolates exhibited significant antibiotic activities against Erwinia amylovora. Isolates have been identified to be Bacillus spp., Pseudomonas spp., Burkholderia spp. and Streptomyces spp. using 16S rDNA sequence analysis. Investigations examined the stability and efficacy of antifungal occidiofungin produced by Burkholderia contaminans strain M14. In addition, characterization of genes associated with antimicrobial activities of bacteria Pseudomonas kilonensis, P. chlororaphis and P. vancouverensis were conducted using Tn5 random mutagenesis and cloning genes associated with antimicrobial activities. Genome drafts of three bacterial strains with antimicrobial activities have been generated A study of bacterial communities present in Andean soils from Ecuador, Chimborazo Province, suppressive to Phytophthora infestans was conducted in cooperation with Carla Garzon using T-RFLP to assess the microbial diversity present in these soils. Bacteria corresponding to at least 13 phyla were identified. Most bacteria belonged to Actinobacteria, Proteobacteria and Firmicutes. Comparisons of suppression of Rhizoctonia solani and Phytophthora infestans between heat treated and non-treated soils suggest that bacteria of the genera Bacillus and Geobacillus are responsible of most of the suppressive nature of these soils. Rhizoctonia populations and diversity are being evaluated by a number of scientists as a part of this project. Enumeration of Rhizoctonia species has been evaluated by the toothpick-baiting technique and selective media across diverse crops and geographic locations. In Arkansas, the diversity of Rhizoctonia spp. in rice soybean cropping systems included R. solani AGs 11, 1-1A, 4 and 2-1, Rhizoctonia oryzae and bi-nucleate Rhizoctonia species. Kirk Borders is examining the diversity of Rhizoctonia solani isolates associated with wheat, canola, soybean, and dry bean by phylogenetic analysis. In Arkansas, the spatial distribution of Rhizoctonia spp. in fields undergoing rice and soybean rotations is being characterized. Rhizoctonia aerial blight of soybean is a disease caused by Rhizoctonia solani AG1-IA. This pathogen also causes sheath blight of rice. Populations and disease assessments were characterized in producers field on a spatial scale to represent the topography of the field intermittent of the rice levee positions. Directional distribution ellipses for distribution of R. solani AG1-IA using soil and plant samples indicated agreement with drainage. Across years, distribution of R. solani AG1-IA appears to be controlled by levee position. Where levees do not form logical areas of collection, the greatest concentration of inoculum appears to be in the lower elevations of the field. The spatial distribution of the early-season inoculum of R. solani AG1-IA reiterates the idea that inoculum in the form of sclerotia and hyphae associated with rice residue may be floating and collecting at lower points within the levees. Interestingly, Rhizoctonia solani AG11 has been recovered from both plant and soil samples with greater frequency and does not follow a similar distribution pattern to R. solani AG1-IA. Spatial data for R. solani AG11 indicated isolation from soybean plants correlated spatially to the driest areas of the fields and improved soybean stands. Objective 2. Examine the effect of traditional or newly developed management strategies (chemical, cultural, and biological), soil physicochemical properties, or introduced biological control agents on the microbial community and its ability to suppress soilborne pathogens. Microbial communities are being characterized from diverse cropping systems as part of this project. In Mississippi, the microbial community present on sweetpotato roots is being characterized to identify the source of the tip/end rot complex using fields planted with Beauregard B-14 cultivar and sampling plant tissues at eight points throughout the growing season and during storage. Symptoms of tip/end rot generally appear in storage roots of sweetpotato after harvest, but have been reported at earlier stages of the growing season. Bacterial cultures were initially subjected to fatty acid methyl ester (FAME) analysis for preliminary identification, followed by molecular analysis using 16S rDNA. Fungal cultures were grouped by general morphology and sequencing of the ITS region for representative isolates or the translation elongation factor 1-alpha (ef1±) DNA region for Fusarium species. Communities appear to shift in relative abundance between the growing cycle and harvest. Bacillus spp., L. enzymogenes, and P. lentimorbus accounted for more than 50% of bacteria identified. No pathogenic bacteria were found, but a number of the species have representatives with known biocontrol activity. The majority of fungi were Macrophomina phaseolina, Aspergillus spp., Trichoderma spp., and a large number of Fusarium spp. In early season samples from seed stock and bedding plants, the community is primarily composed of Fusarium spp., nearly 70%. Post-harvest samples show differences in relative abundance of the dominant species, with M. phaseolina increasing to an average of 6.5% in samples taken from storage, and Fusarium spp. decreasing to an average of 27% between 60 and 90 days post-harvest. To date, isolates found to be pathogenic on sweetpotato are Fusarium species and Macrophomina phaseolina. The effect of perennial ryegrass cultivar mixtures on soil microbial communities is being examined in the Northeast US. A multi-location field trial was established in Maine, New Hampshire, New York, and Vermont to examine the effect of perennial ryegrass cultivar mixtures on soil and foliar microbial communities. Chloride salts have been demonstrated to increase the incidence of Phytophthora root and stem rot of soybean by changes in the micro-partitioning of calcium in the soybean roots. In Tennessee, the value of supplementary calcium added to a common soybean seed treatment, mefenoxam + fludioxonil + thiamethoxam, on seed germination and seedling growth was examined. Treated seed were planted in solarized field soil and later evaluated for their effect on seedling root rot in greenhouse and field in soils infested with Rhizoctonia solani, Macrophomina phaseolina, Pythium spp. and Fusarium spp. The effects of treatments on the concentration of calcium in the outer cell layers of soybean roots was determined with an Environmental Scanning Electron Microscope (ESEM) using energy-dispersive X-ray analysis (EDX). Best seedling growth was observed when the mefenoxam + fludioxonil + thiamethoxam seed treatment was supplemented with 4% calcium formate, 1% calcium nitrate, 4% calcium lactate, and 2% calcium salicylate in the absence of pathogens. Stands of healthy plants in the field were initially highest when the mefenoxam + fludioxonil + thiamethoxam seed treatment was supplemented with calcium lactate in unfertilized plots but were later highest with the calcium salicylate supplement in plots receiving muriate of potash. While the seed treatments had no effect on the level of many nutrients in seedling roots, the levels of calcium, magnesium, potassium, and phosphorus were significantly increased with the mefenoxam + fludioxonil + thiamethoxam seed treatment compared to the untreated control. Supplementing the mefenoxam + fludioxonil + thiamethoxam seed treatment with calcium nitrate or calcium salicylate significantly increased the level of potassium in seedling roots compared to the control. Research on the use of soil amendments and cover crops on disease suppression is continuing as part of the project. In New Hampshire, cover crops for suppression of Verticillium dahliae on strawberry and mint are being evaluated initially by screening strawberry accessions and a variety of cover crops for their ability to resist infection and suppress inoculum levels of the soilborne pathogen V. dahliae. The impact of fungicides and heavy metals were also being investigated by project scientists. Fungicide hormesis was assessed in vitro on Pythium irregulare, Sclerotinia homoeocarpa, and Botrytis cinerea, validating the stimulation of pathogen activity by low fungicide levels. Heavy metals impact soil biological activity primarily by binding with enzymes and changing the configuration of the enzyme preventing enzymes catalyzing the conversion of substrate to product. Research in Iowa is examining the effects of six heavy metals (Cd, Co, Cr, Cu, Ni, and Pb) of the legumes Vicia faba, Trifolium alexandrium, and Glycine max. Results showed that plant weight, nodulation, and N uptake decreased significantly with increasing heavy metal concentrations, from 0 to as high as 4.3 mmol per kg soil. Plots of the natural log of each of the three parameters against metal concentration were linear. From the slopes of these lines, the concentrations of each metal required to produce 50% reduction in the parameter were calculated. Results showed that values varied among the soils and legumes studied but, in general, the lowest metal concentrations for 50% reduction (i.e., the most toxic) heavy metals were Cd and Pb.

Peer-reviewed Abd-Elmagid, A., Garrido, P.A., Hunger, R., Lyles, J.L., Mansfield, M.A., Gugino, B.K., Smith, D.L., Melouk, H., and Garzon, C.D. Discriminatory simplex and multiplex PCR for four species of the genus Sclerotinia. Journal of Microbiological Methods. Accepted Brewer, C. E., Hu, Y., Schmidt-Rohr, K., Loynachan, T. E., Laird, D. A., and Brown, R. C. 2012. Extent of pyrolysis impacts on fast pyrolysis biochar properties. J. Environ. Qual. 41:1115-1122. Ellis, D., Gosai, J., Emrick, C., Heintz, R., Romans, L., Gordon, D., Austin, F., Lu, S.-E., and Smith, L. 2012. Occidiofungin's chemical stability and in vitro potency against Candida species. Antimicrobial Agents and Chemotherapy 56:765-769. Flores, F.J., and Garzon, C.D. 2012. Detection and assessment of chemical hormesis on the radial growth in vitro of oomycetes and fungal plant pathogens. Dose-Response. Accepted, early view on-line Garzon, C.D., Molineros, J.E., Yanez, J.M., Flores, F.J., Jimenez-Gasco, M.M., and Moorman G.W. 2011.Sublethal doses of mefenoxam enhance Pythium damping-off of geraniums. Plant Disease 95:1233-1238. Garzon, C.D., and Flores, F.J. 2012. Hormesis: biphasic dose-responses to fungicides in plant pathogens and their potential threat to agriculture. In: Nita M. 2012. Tan, W., J. Cooley, F. Austin, S.-E. Lu, L. Smith and S. Pruett. 2012. Nonclinical toxicological evaluation of occidiofungin, a unique glyco-lipopeptide antifungal. International Journal of Toxicology 31:326-36. Abstracts Haddad, S. A., M. A. Tabatabai, A. A. Abdel-Moneim, and T. E. Loynachan. 2011. Effects of concentration of selected heavy metals on nodulation and nitrogen nutrition of leguminous crops. 363-8 Agron. Abstracts, Madison. Spurlock, T., Rothrock, C., and Monfort, W. 2012. Spatial assessment of Rhizoctonia solani in fields undergoing rice and soybean rotations. (Abstr.) Phytopathology 102:S4.113. Spurlock, T. N., Rothrock, C. S., and Monfort, S. 2012. Comparison of methods for isolation and quantification of Rhizoctonia spp. from field soil. (Abstr.) Phytopathology 102:S2.9. Other publications Loynachan, T. E. 2012. Life in the soil: Who cares? pp. 28-30. In Deborah McDonough (ed.) Getting Into Soil and Water. Iowa Water Center, Ames, IA.