A Spray Inoculation Technique to Establish Fungal Infection in Rice Plant Leaves
JoVE Encyclopedia of Experiments
Immunology
0 views • 3:30 min • July 8th, 2025
Take a Petri plate with sections of rice plant leaves positioned above a wet filter paper to prevent desiccation.
Take a suspension of conidia — reproductive spores — of the pathogenic fungus Magnaporthe grisea. Spray on the leaf sections and incubate under dark and humid conditions.
Moisture induces conidia to release mucilage, facilitating attachment to the leaf surface.
The conidia extend germ tubes, the tip of which differentiates into dome-shaped appressorium.
High solute concentration inside the appressorium generates turgor pressure, forming a penetration peg.
The small diameter of the peg focuses turgor-mediated force on a small leaf area, causing penetration into the leaf cell.
The peg differentiates into invasive hyphae to derive nutrition.
Incubate the leaf sections under fluorescent light for fungal growth.
The hyphae ramify within infected cells and invade neighboring cells through plasmodesmata.
The fungus secretes toxins to induce necrosis, resulting in leaf lesions. Score the lesions to assess infection severity.
Use sterile surgical scissors to cut three layers of filter paper into 8-centimeter circles. Place the filter paper circles onto 100-millimeter sterile plastic plates. Add just enough distilled deionized water to each dish to soak the filter paper. Then, place two sterile toothpicks 2 to 3 cm apart in each culture dish.
Two weeks after sowing, collect the leaves of the rice plants by cutting the lower part of the stem. Using a thermostatic incubator, culture the M. grisea strains on OTA plates at 25 degrees Celsius for four days. Then, use a pipette to add 2 milliliters of distilled deionized water to each plate. Using an inoculation loop, scrape the mycelia from the wild-type and mutant strains into the mycelia debris.
Collect the mycelia debris, and transfer it to a new OTA plate. Then, dry the mycelia debris on a clean bench. Add 2 milliliters of distilled deionized water to the cultured mycelium dish, and use a sterile cotton swab to gently scrape the conidia. Filter the conidia suspension through two layers of lens paper, and transfer the suspension to a new 50-milliliter tube. Then, centrifuge the tube for 5 minutes at 5,000 times g.
After centrifugation, remove the supernatant, and resuspend the pellet with Tween 20 solution, resulting in a concentration of 20,000 conidia per milliliter. Pour the suspension into a hand-held sprayer. Then, spray approximately 10 milliliters of the conidial suspension onto the leaves from the two-week-old rice plants. Spray the leaves of the control plants with Tween 20 solution.
After this, incubate the leaves in a dark humid box for 24 hours. Next, transfer the leaves to a moist chamber with fluorescent light for 12 hours.
Overview
This study investigates the infection process of the rice plant by the pathogenic fungus Magnaporthe grisea. The methodology involves the application of conidia to rice leaves and the subsequent observation of fungal growth and infection severity.
Key Study Components
Area of Science
- Plant pathology
- Mycology
- Fungal infection mechanisms
Background
- Magnaporthe grisea is known for causing significant damage to rice crops.
- The infection process involves the attachment of conidia to the leaf surface.
- Understanding this process can help in developing strategies for disease management.
- Previous studies have focused on the mechanisms of fungal attachment and invasion.
Purpose of Study
- To elucidate the infection process of M. grisea on rice plants.
- To assess the severity of infection through lesion scoring.
- To explore the conditions that facilitate fungal growth and invasion.
Methods Used
- Preparation of rice leaf sections on wet filter paper.
- Application of conidia suspension to the leaf sections.
- Incubation under controlled dark and humid conditions.
- Assessment of fungal growth and lesion formation.
Main Results
- Conidia successfully attached and germinated on rice leaves.
- Formation of appressorium and penetration peg was observed.
- Fungal hyphae invaded leaf cells and neighboring cells.
- Lesions formed on leaves indicated the severity of infection.
Conclusions
- The study provides insights into the infection dynamics of M. grisea.
- Understanding these mechanisms can aid in developing resistant rice varieties.
- Future research may focus on the molecular interactions during infection.
Frequently Asked Questions
Executive Industry Relevance
Spray inoculation of rice leaves with Magnaporthe grisea conidia provides a standardized model for evaluating host-pathogen interactions and quantifying disease progression. This approach enables reproducible assessment of fungal virulence and plant susceptibility, supporting early-stage target validation and mechanistic de-risking in crop protection R&D. The method's quantitative lesion scoring informs predictive confidence for translational research and portfolio triage.
Strategic Applications in Biopharma R&D
Early Discovery & Target Validation
- Enables interrogation of host-pathogen interactions and identification of disease-relevant pathways.
- Supports biological de-risking by clarifying infection mechanisms and host response.
- Facilitates predictive confidence in selecting genetic or chemical intervention points.
Screening & Assay Development
- Establishes a validated, reproducible infection model for downstream screening workflows.
- Provides quantitative lesion scoring as a standardized output for assay development.
- Enables reliable evaluation of candidate compounds or genetic modifications for antifungal efficacy.
Translational & Preclinical Research
- Aligns with disease-relevant systems for translational biomarker discovery in crop protection.
- Supports continuity from early discovery through preclinical validation of resistance traits.
- Informs risk-adjusted advancement decisions for trait or compound development pipelines.
Pipeline & Workflow Integration
This spray inoculation technique positions within the discovery-to-preclinical continuum for crop disease research, enabling hypothesis testing, screening, and translational validation.
- Discovery Biology: Facilitates hypothesis-driven testing of infection mechanisms and host responses.
- Screening: Provides reproducible, quantitative lesion scoring for comparative analysis of interventions.
- Analytics: Delivers measurable outputs to support statistical comparison of experimental conditions.
- Translational Research: Bridges early discovery findings to preclinical validation in disease-relevant plant systems.
- Enterprise Reuse: Offers a standardized infection model adaptable across genetic backgrounds and intervention strategies.
Operational & Enterprise Impact
- Scientific Value: Increases predictive confidence and reduces mechanistic ambiguity in host-pathogen studies.
- Operational Value: Enhances reproducibility and scalability for high-throughput screening and comparative studies.
- Strategic Value: Improves go/no-go decision-making and capital efficiency in trait or compound advancement.
- Portfolio Impact: Supports risk-adjusted prioritization of resistance traits or antifungal candidates.
Implementation Considerations
- Requires expertise in plant pathology and fungal culture techniques.
- Needs controlled environmental conditions for incubation and infection assessment.
- Demands standardized lesion scoring protocols for cross-team comparability.
- Adaptable to different rice varieties or fungal strains with protocol optimization.
- Dependent on consistent conidia preparation and application for reproducible results.
Biopharma FAQs
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Last updated: 29 August 2026