Lab 3

Objectives

 1. To collect the diseased plants with visible symptoms and signs in the field

2. To preserve the diseased plant samples for isolation and identification in the laboratory

Materials 

Each student or team of students will require the following items: 

• Plastic bag and paper bags

• Shovel an Scissors

• Gloves

• Field collection data sheet

• Dry newspaper

• Marker pen

• Disinfectant for hands and tools

Procedures

A. General guidelines for plant sample collections

1. All parts of the plants, such as leaves, branches, stems, fruits, and roots with visible disease symptoms, were carefully examined. All infected plant parts were collected.

2. All tools and equipment used to cut the specimen were sanitized to avoid further contamination and damage to the collected samples.

3. More than one plant sample was collected, as a single sample was not sufficient for correct and accurate diagnosis. Samples were collected at various stages of disease infection (early and late infections).

4. Dead plant parts were avoided, as isolating a pathogen from a dead host was difficult.

5. For plant disease sampling in a field, students used a zig-zag pattern to randomly collect the samples.

6. In cases where diagnosis depended on only certain parts of the plant, and it was difficult, the entire plant was collected if possible. The plant was carefully dug from the ground, ensuring the roots remained intact and undamaged.

7. The presence of signs of the pathogen in the field or infected area was observed, such as the formation of spores or mycelium, bacterial ooze, or the appearance of insects.

8. Background information related to the field or sampling area, such as crop history, growing practices, previous disease infections, management, and environmental conditions, was recorded.

B. General guidelines for preservation and labelling of the plant samples

1. All samples were handled carefully and kept in moist, cool, and dry conditions to avoid contamination and damage. Direct exposure to sunlight was avoided.

2. The collected samples, such as leaves, stems, and roots, were placed in sealed plastic containers to maintain moisture and prevent the samples from drying out.

3. Large leaf samples were wrapped individually in dry newspaper.

4. Fleshy fruits and vegetables were placed in paper bags or wrapped with a few layers of dry newspaper.

5. The samples were labeled accordingly with necessary information, including:

• Date

• Location

• Types of samples

• Name of suspected disease

• Possible causal agents

6. The samples were brought to the laboratory as soon as possible and kept in a refrigerator or a moist chamber for isolation and identification.

Results

Discussion

1. List five examples of biotic or abiotic agents that caused plant disease. 

-In result

2. Summarize all the important processes in plant disease collection using a simple diagram or flowchart. 

-In result

Conclusion

In conclusion, the detailed procedures for collecting and preserving diseased plant samples provide a comprehensive framework for accurate diagnosis and effective laboratory analysis. The systematic collection process ensures all relevant parts of the plant, from leaves to roots, are carefully examined and sampled, while the use of sanitized tools minimizes the risk of contamination. By adopting a zig-zag sampling pattern and collecting multiple specimens at different stages of infection, students enhance the reliability and accuracy of their findings. The preservation guidelines further underscore the importance of maintaining sample quality by avoiding direct sunlight, ensuring proper moisture levels, and using appropriate packaging materials like plastic bags, paper bags, and dry newspapers. Proper labeling with critical information, such as date, location, and suspected disease, facilitates efficient tracking and analysis in the laboratory. Overall, this methodical approach not only aids in the successful isolation and identification of plant pathogens but also equips students with practical skills essential for plant disease management and research. By following these best practices, a deeper understanding of disease progression and its causal agents can be achieved, supporting informed decisions for crop health and agricultural sustainability.