Project Number: 1230-22000-022-00
Project Type: Appropriated

Start Date: Apr 09, 2007
End Date: Apr 08, 2012

Objective:
The overall goal of this project is to provide the means for growers to control viral and bacterial diseases of ornamentals using environmentally friendly practices. We will investigate and characterize viruses and bacteria of major significance in ornamental and nursery crops, and develop serological reagents, molecular probes, and diagnostic technologies. Accurate and sensitive diagnostic methods will allow identification of viral and bacterial diseases, and selection of healthy stock for propagation (exclusion of disease). There is no known effective natural resistance against viral and bacterial diseases in many ornamentals. We will therefore investigate the genome organization of important viruses of ornamentals, and determine which genes are involved in host range, pathogenicity and symptom induction. An understanding of the factors involved in viral and bacterial pathogenesis may allow development of effective means of interference in the disease process. Examining host/pathogen interactions of Ralstonia solanacearum will lead to increased understanding of the epidemiology of bacterial wilt disease in geranium. Botanical extracts effective against soil-borne fungi will be examined to determine if they can control bacterial wilt in this important crop. Studies of host and vector specificity of strains of Xylella fastidiosa are expected to result in development of strain-specific diagnostic methods, and epidemiological information. This knowledge will be used to target interventions for improved disease control.

Approach:
Characterize viruses of major significance to ornamental and nursery crops, including "new" currently uncharacterized or emerging viruses affecting key ornamental crops. The overall approach is to develop knowledge, tools, and reagents that will aid U.S. floriculture companies in establishing effective virus testing protocols that will improve clean stock production for new vegetatively propagated annuals and perennials. Research will initially focus on those "new" currently uncharacterized or emerging viruses affecting key ornamental crops recently identified as significant to the floral and nursery industry, including those infecting petunia, impatiens, phlox and pansy. Viruses of serious consequence identified as significant to the floral and nursery industry in key ornamental crops also include, but are not limited to: Arabis mosaic virus and Cucumber mosaic virus, carlaviruses, carmoviruses, closteroviruses, fabaviruses, ilarviruses, pelarspoviruses, potexviruses, potyviruses, and tobamoviruses. Based on the knowledge and serological reagents, and molecular probes developed for the detection and management of diseases caused by the viruses characterized above, new virus-specific and broad-spectrum polyclonal and/or monoclonal antibody reagents, purification protocols, molecular nucleic acid hybridization probes, PCR primers, and improved associated protocols and diagnostic technologies will be developed. Determine the genome organization of selected important ornamental viruses and develop full-length infectious clones to determine the genes or gene products involved in pathogenicity. Understanding viral genome structures and functions, the mechanisms of pathogenicity, and the mechanisms of resistance in plants will lead to the development of better viral disease control measures and increases in both productivity and quality of ornamental plants. Develop improved tools and evaluate methodologies for the identification, detection, and control of bacterial diseases of major significance to woody and floral ornamental crops. Conduct research on the host range and environmentally friendly control of bacterial wilt disease of geranium caused by the select agent pathogen Ralstonia solanacearum race 3, biovar 2. Conduct research on the identification and detection of Xylella fastidiosa in ornamental crops, study the genetic relationships among strains of X. fastidiosa, and determine the pathogenetic relationships between ornamental and non-ornamental strains of X. fastidiosa. BL1/BL1P 3/5/07; BL1/BL2P 3/4/07.