Plant Diseases (Edexcel GCSE Biology)

Detecting & Identifying Plant Disease

Higher tier only

• Plants can be infected with a range of bacterial and viral pathogens; such as the tobacco mosaic virus (TMV) and rose black spot fungus (see Viral Diseases & Fungal Diseases)

• Plants can also be infested with insects such as aphid which pierce the surface of the stem and  feed off the sap in phloem causing physical damage and weakening the plant

• The symptoms of plant diseases can apply to more than one disease, which makes identifying them difficult

• Symptoms of diseases in plants include:

Plant Diseases Table

Detecting and identifying plant diseases in the field

• Studies of plant species in their natural environment might highlight the presence of certain diseases

• Observations by plant pathologists would be carried out and diseases identified based on symptoms

  • Chalara ash dieback causes leaf loss and bark lesions

  • Aphids cause physical damage to the stems of plants

• When a symptom of a disease has been detected, it is important to determine whether it is due to the proposed disease or an environmental issue, such as mineral ion deficiency

• Assessing the distribution of the plant populations also may indicate what type of pathogen is involved and/or how it is being transmitted

  • Patches of diseased plants may suggest infection through the soil

  • Random distributions may suggest airborne transmission such as the spores which cause Chalara ash dieback

Detecting and identifying plant diseases in the laboratory

• In order to do a more detailed assessment of plant disease, ecologists may take cuttings of plants to return to a laboratory for chemical analysis

• Culturing the pathogen from the sample taken may lead to accurate identification of the disease

  • Monoclonal antibodies can be used:

    • These are antibodies that are specific to the antigens on the pathogen

    • If the antigen is present in the infected plant sample, the antibodies will bind to them and allow accurate diagnosis of the disease

  • DNA analysis in the laboratory would help to identify the specific pathogen causing the problem