Pathogen Screening
Molecular Diagnostics
Move beyond visual symptoms. Molecular screening utilizes PCR and isothermal amplification to identify vascular pathogens and viroids at the DNA/RNA level long before an outbreak occurs.
The Methodology
Select a workflow to view the molecular mechanisms at work.
Cell Lysis
Breaking the Wall
Chemical Extraction
Before we can detect pathogen DNA, we must chemically break open plant cell walls and purify the genetic material, stripping away proteins and polysaccarides.
Primer Binding
Target Selection
Specific Targeting
Synthetic DNA sequences (primers) are introduced. They hunt through billions of base pairs to bind strictly to the unique genetic code of the target pathogen.
PCR Amplification
Thermal Cycling
Polymerase Action
Using a thermocycler, rapid shifts in temperature denature DNA and drive exponential replication. One copy becomes millions within an hour.
Fluorescence
Optical PCR Detection
Real-Time Sensors
As target DNA replicates in a PCR machine, fluorescent probes bind to the strands. An optical sensor reads this glowing signal to confirm a positive result.
LAMP Amplification
Isothermal Alternative
Constant Heat
Unlike PCR, Isothermal Amplification (LAMP) utilizes specialized enzymes to continuously replicate DNA at a steady 65°C, providing incredibly rapid field diagnostics.
Colorimetric
Visual LAMP Detection
pH Shifts
In Isothermal amplification, rapid DNA replication alters the pH of the buffer. This causes an immediate, naked-eye color change from pink to yellow if the pathogen is present.
Diagnostic Efficacy
Why molecular testing supersedes traditional visual or culture-based pathology.
Diagnostic Pitfalls
Vulnerabilities in PCR and how high-complexity labs mitigate them.
PCR Inhibition
False Negatives
Chemical Blockade
Plant resins, polyphenols, and polysaccharides can bind to the polymerase enzyme, halting amplification. If untreated, a sick plant will incorrectly test negative.
Cross-Contamination
False Positives
Aerosolized Amplicons
PCR creates millions of DNA copies. If a tube is opened improperly, aerosolized DNA will float into neighboring samples, causing clean plants to test positive.
Operational Excellence
Throughput forecasting and diagnostic mitigation.
1. PCR Results Matrix
Technician Observation: An assay yielded unexpected data. Diagnose the run.
2. 96-Well Throughput
Required Plates
QC Controls Used
3. SOP Verification
- Accessioning Confirmed
Barcodes scanned and synced with LIMS manifest. - Master Mix Prepped
Primers, probes, and polymerase mixed in a clean-hood. - Amplification Validated
Internal controls amplified within expected Ct range. - Target Pathogen Analyzed
Samples evaluated against pathogen-specific thresholds. - QA Sign-off
Data curves reviewed; CoAs automatically generated.