Plant diseases Flashcards
What questions would you ask in distribution analysis?
-How many plants are affected?
If all are affected it is probably an environmental factor, like soil pH
-Are the infected plants close together or in a wide range?
- Where are they found?
(e. g. next to a road that might indicate pollutants)
-Is it just one species or several?
(it could be a species-species pathogen)
-Are the infected plants in all directions or just one?
(Could be a fungus spread by wind)
-Do the symptoms of the plant change over time?
What tests are done in the laboratory?
- microscopic examination of plant material for signs of pathogens
- antibodies to test for the presence of a pathogen
- genetic testing to identify any pathogens found
- soil sample testing to rule out soil factors, e.g. nutrient deficiency
- trying to grow pathogens on nutrient medium to produce a larger sample for identification
What can plant diseases be caused by?
environmental factors
nutrient deficiency in the soil
pathogens such as fungi
water levels
sunlight levels
pests
How can diseases be identified in the field?
visible symptoms
Describe the types of visible symptoms
Change in appearance of the plant (different colour of flowers or leaves)
Lesions/damage to the leaves and stem
Change in growth (overgrowth or underdevelopment of plant)
e.g. swellings on roots or smaller leaves
Death of parts of the plant (dead leaves or roots)
Why are tests needed to confirm the cause?
different diseases have very similar/the same symptoms
the same disease can have symptoms that look different on different plants
What is distribution analysis?
looking at the way diseased plants are distributed in the environment to identify the possible causes of disease
What can be done if the disease can’t be identified?
A sample of plant material and soil can be sent to a laboratory for testing.
A scientist found a diseased plant. He thought the disease was caused by a fungus. Describe how he could prove this.
The scientist could place some of the diseased plant onto an agar dish to grow some of the fungus.
The scientist could then isolate some of the fungus and grow a pure culture on a new agar dish.
The scientist could infect a healthy plant with some of the fungus.
If the plant develops the same symptoms as the original diseased plant, it shows that the fungus did cause the disease symptoms in the original plant.
Laboratories that carry out disease identification for farmers ask for a sample of plant material and of soil in which the plant was growing.
Explain why they ask for these samples.
soil sample can be tested to see if a soil factor is causing the symptoms
plant material always scientists to see the symptoms
can examine plant material with a microscope (to look for pathogens)
