10 Questions
Why is it essential to collect an adequate sample for diagnosis?
To prevent contamination by secondary microorganisms
What is the primary reason for avoiding dead plants as samples?
The plant pathogen may not have survived on dead tissue
What is the purpose of surface-sterilization in plant diagnosis?
To eliminate saprophytic microorganisms from the plant tissue
What is the recommended method for surface-sterilization?
Soaking the tissue in a 10-20% bleach solution
When is it necessary to collect whole plants for diagnosis?
When there is suspicion of root problems contributing to foliar symptoms
Why are soil samples sometimes collected around damaged and healthy plants?
To understand the role of soil pH or nutrients in the plant problem
What is the primary concern when collecting samples from trees?
Collecting the whole plant is not possible
What is the ideal size of a turf grass sample for diagnosis?
A 7" × 7" area with sufficient depth to include the roots
Why is it essential to collect a representative sample from symptomatic or suspected parts of a plant?
To ensure the sample is representative of the whole plant
What is the primary advantage of collecting an adequate sample for diagnosis?
It ensures accurate detection of plant pathogens
Study Notes
Pathogen Detection and Identification
- Common methods used for pathogen detection and identification include ELISA, Western blot, Immunofluorescence microscopy, and Rapid Immunodiagnostic Tests.
- Biochemical methods employed include Enzyme Assay, Protein/Metabolite Profiling, RNA and Gene Expression Analysis.
- Molecular analytical methods used include PCR-based detection assays, Real-time Quantitative PCR (qPCR), Polymerase Chain Reaction (PCR), Loop-mediated Isothermal Amplification (LAMP), and Next-generation Sequencing (NGS).
Pathogenicity Test
- Pathogenicity test is the ultimate test to demonstrate proof of pathogenicity.
- The test involves reproducing the damage using the suspected pathogen.
- Sterilization of plant material is necessary before testing, usually done with ethanol, peroxide, or n-alkyl products.
- Exposure time to the sterilizing agent ranges from a few seconds to several minutes, depending on the structure of the plant tissue.
Pathogen Culture
- About 85% of plant diseases are caused by fungi.
- Sterile tissue samples are sectioned and placed on sterile media culture (petri dishes).
- Culture is maintained at room temperature or in an incubator at a specific temperature (e.g., 28°C–30°C for bacterial growth or ~25°C for fungal growth).
- The type of media culture is important for the type of microorganism to be isolated.
Serological Methods
- Serology is the study of immunological reactions between antigens and antibodies.
- Adequate sample collection is necessary for a proper diagnosis, and the sample size varies depending on the type of problem and plant.
Sample Collection and Preparation
- Avoid dead plants as samples, as they may not have surviving pathogens or may be overrun with saprophytic microorganisms.
- Collect representative samples from symptomatic or suspected parts, or whole plants if possible.
- Soil samples may be necessary when soil pH or nutrients are suspected to be contributing to the plant problem.
Isolation and Recovery
- Surface-sterilization is necessary to reduce surface contaminants and saprophytes.
- The most common method is soaking the tissue in a diluted bleach solution (e.g., 10-20% or 0.5–1% NaOCl).
This quiz covers various immunological assay methods, including ELISA, Western blot, Immunofluorescence microscopy, and Rapid Immunodiagnostic Tests, used to identify unknown bacteria.
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