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United States Department of Agriculture

Agricultural Research Service

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Research Project: Detection and Identification of Soil-borne Plant Pathogens and Mitigation of Soil-borne Diseases

Location: Floral and Nursery Plants Research Unit

2013 Annual Report


1a.Objectives (from AD-416):
Develop molecular tools to detect, identify, characterize, and counteract the pathogenicity of soilborne pathogens, such as Rhizoctonia solani in ornamental crops and turfgrasses. Examine episomal and chromosomal genetic elements affecting biology or virulence of R. solani. Analyze gene expression of important soilborne pathogens, such as R. solani, to understand the virulence of the organism. Evaluate transgenic plants, including ornamentals for resistance to fungal pathogens. Improve the efficacy and consistency of biological control agents for important soilborne pathogens (Rhizoctonia, Fusarium and Ralstonia) through combination with organic amendments, new and safer chemicals, composts, and reduced-risk fungicide(s). Screen plant extracts and reduced-risk chemicals with broad spectrum properties against soilborne pathogens. Study structure/activity relationships of potential reduced-risk chemicals from plant extracts for understanding biocidal effects on R. solani or other pathogens. Investigate the combined effectiveness of bio-fumigation and/or soil-treatment with botanical extracts, antagonistic microbe(s), reduced-risk chemicals, or compost made from pine needles to control soilborne pathogens.


1b.Approach (from AD-416):
Utilize molecular approaches such as UP-PCR, rDNA sequencing, etc. to distinguish pathogenic Rhizoctonia isolates and to group them. Construct expressed gene cDNA libraries of virulent and hypovirulent Rhizoctonia isolates, and analyze to identify differentially expressed genes. Develop transformation system for R. solani. Evaluate transgenic gladiolus for resistance against Fusarium oxysporum, fsp gladioli. Screen to identify plant extracts inhibitory to R. solani and other soilborne plant pathogens. Evaluate antagonistic fungi, bacteria, or other microbes to check their effectiveness alone or in combination with biorationals or soil amendments in controlling soilborne pathogens of ornamental crops.


3.Progress Report:
This report bridges the research documented under 1230-22000-029-00D which expired on May 19, 2013.

Progress was made on Objective 1. Using a high throughput approach, we sequenced the genome of selected isolates of Rhizoctonia solani in order to identify key genes useful for identification of selected anastomosis groups of the pathogen and for deciphering virulence of the pathogen. Additional information for this project is available in the report of project 1230-22000-029-02S. Additionally, we have initiated investigations of the fungal pathogen Cylindrocladium pseudonaviculatum, the causal agent of boxwood blight, to determine genome biology, ecology, and overwintering. We are transforming the pathogen with a hygromycin resistance gene and a fluorescence reporter gene. We are also conducting genomic and transcriptomic analysis by high throughput sequencing.


Last Modified: 9/23/2014
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