Recipient Organization
NORTH CAROLINA STATE UNIV
(N/A)
RALEIGH,NC 27695
Performing Department
Entomology and Plant Pathology
Non Technical Summary
Non-Technical SummaryIn North Carolina peaches are grown for fresh market and are sold mostly at the farm and at farmers' markets within the State. Fresh peaches provide a local source of income for numerous small, family farms. Peach fruit are susceptible to many diseases caused by fungal and bacterial pathogens. The peach tree also is susceptible to some of the same diseases and additionally to viruses and nematodes. Because of the warm, moist growing conditions in North Carolina and the Southeast, fruit diseases can be very destructive and fungicides are used to successfully produce marketable fruit. Fortunately, there are very effective fungicides available to control the major fungal fruit diseases. There are two important bacterial diseases that can cause significant fruit and tree losses in North Carolina and the Southeast, bacterial spot (Xanthomonas arboricola pv. pruni) and bacterial canker (Pseudomonas syringae pv syrinage). Control for these two bacterial diseases of peaches and for other bacterial plant diseases in general are sorely lacking. There are few available antibacterial chemicals or biologicals and these are not very effective when diseases are moderate to severe. The few chemicals, mostly copper and the antibiotic oxytetracycline must be applied at very critical times just prior to bacterial infection to achieve at least some acceptable degree of disease control. To do this requires knowledge of the epidemiological conditionals for infection resulting in bacterial spot of peach fruit. Using 20+ years of epidemiological data, it is possible to better define the critical infection periods for bacterial spot fruit infection. This will allow the grower to make more timely sprays and possibly reduce unnecessary sprays.There are many microorganisms on plant surfaces including pathogens, non-pathogens, and bacterial viruses that specifically infect bacteria (bacteriophages or phages). Bacteriophage viruses are the most abundant entity on earth. Yet, knowledge is sorely lacking how these microbes interact on the phyllosphere of plants. Phages can potentially have several effects on bacterial populations. Phages can specifically kill their bacterial host or hosts thus regulating bacterial population numbers, they can be transporters of genetic material, and some can provide their bacterial host with virulence factors. Given the extreme abundance of phages, relative few phage genomes have been sequenced and compared particularly those of plant pathogenic bacteria. The project director has a collection of Xanthomonas bacteria and phages. This collection will provide samples that will be sequenced and annotated to ultimately conduct a metagenomics analysis. Together, this collection of bacteria and phages has a detailed known history that includes bacterial host characteristic, niche origin (tissue and type) and environmental factors that will provide a thorough examination of the ecology and diversity governing Xanthomonas-phage interactions. This could lead to novel bacterial disease control methods including novel uses of phages for bacterial disease management.
Animal Health Component
30%
Research Effort Categories
Basic
50%
Applied
30%
Developmental
20%
Goals / Objectives
A.Refine the knowledge base for host and environmental conditions required for infection of peach fruit by the bacterial spot pathogen Xanthomonas arboricola pv. pruni (Xap). B.Characterize the ecological and molecular association in bacteriophage - Xanthomonas species interactions
Project Methods
PROCEDURES:A. Refine the knowledge base for host and environmental conditions required for infection of peach fruit by the bacterial spot pathogen Xanthomonas arboricola pv. pruni (Xap).Observations strongly suggest that there is a 2-3 week time during which peach fruit are very susceptible to infection. Infection and disease severity depend greatly on moisture conditions during the period of fruit susceptibility. Infection and disease severity depend on fruit growth stage and environmental conditions such as length of periods of moisture and characteristics of the moisture period (free water, relative humidity, wind-driven rain vs moisture saturation, etc), and temperature. Improved forecasting for infection by X. arboricola pv. pruni and the development of bacterial spot symptoms will be accomplished through analysis of weather, tree (fruit) growth phenology and disease data collected during the last three decades on susceptible peach varieties located at the NC Sandhills Research Station. Statistical regression will be used to estimate correlations among the different factors. The outcome is to provide growers a decision support system for applying protective materials such as copper based on predicted infection events. The accuracy of the predication will be evaluated by monitoring weather and tree conditions and then the subsequent bacterial spot development. A diversity of peach cultivars having a range of bacterial spot susceptibility is available at the NC Sandhills Research Station.B. Characterize the ecological and molecular associations in bacteriophage - Xanthomonas species interactions.Bacteriophages and their bacterial host population dynamics will continue to be monitored at least monthly on peach trees located at the NC Sandhills Research Station. Primary tissues monitored include leaves on the tree and on the ground, cankers, and fruit. Weather conditions are monitored at the Research Station and stored in the database of The North Carolina Climate Office (http://climate.ncsu.edu/). Because X. arboricola pv. pruni overwinters on it host, the peach tree, this provides a good system to study the population dynamics of the bacterial host (Xap) and its phages under natural, field conditions. Methods to monitor the phage and its bacterial host population dynamics will utilize traditional phage assays, PCR-based assays, and metagenomics. An expected outcome would be an understanding of whether and how phages affect not only their bacterial host but also a bacterial disease epidemic such as bacterial spot of peaches. Phages also have been detected in association with many plants diseased with many Xanthomonas species and pathovars. A major source of these diseased plants is the NC Plant Disease and Insect Clinic as well as home garden centers. These sources will be used to continue to increase the Xanthomonas and phage collection housed in the Ritchie lab at NC State University. This collection will provide environmental samples that will be sequenced and annotated to ultimately conduct a metagenomics analysis. Some of the isolates from peaches were collected starting in the 1980s and are still viable. Together, this collection of bacteria and phages has a detailed known history that includes bacterial host characteristic, niche origin (tissue and type) and environmental factors will provide a thorough examination of the ecology and diversity governing Xanthomonas-phage interactions over almost four decades.The traditional and current method for using phages in the field for controlling bacteria diseases has focused on applying them similar to the method of pesticide application; spraying them on the plant. Other methods for using phages to potentially manage bacterial plant diseases will be explored and evaluated using both laboratory and field experiments.