Microorganism News

An introduction to plant pathogen

What is plant pathogen?

A plant pathogen is a broad term that refers to any of the organisms, such as fungi, bacteria, protists, nematodes, and viruses that cause plant diseases. Plant pathogens are of interest for a number of reasons, ranging from concerns about fragile ecosystems to the desire to protect the food supply. Plant pathogens that cause plant diseases reduce a grower’s ability to produce crops and can infect almost all types of plants.

plant pathogen

Plant pathogen symptoms

Plants are attacked by different groups of pathogens individually or sometimes by more than one pathogen-producing complex and more severe disease. The type of external symptoms can, in most cases, indicate the nature of the pathogen responsible for the disease. Plant pathogens can attack in a number of different ways. Some colonize the tissue in the plant, others settle on the surface of the plant, and others may go for specific areas such as the roots, stems, and leaves. Pathogens commonly cause problems like tissue death, browning, a decrease in fruiting, problems with setting flowers, and so forth. In extreme cases, they can kill the host plant.

Here are a few examples of common signs and symptoms of fungal, bacterial and viral plant diseases:

Fungal disease symptoms Bacterial disease symptoms Viral disease symptoms
Birds-eye spot on berries (anthracnose)

Damping off of seedlings (phytophthora)

Leaf spot (septoria brown spot)

Chlorosis (yellowing of leaves)

Leaf spot with yellow halo

Fruit spot


Crown gall

Sheperd’s crook stem ends on woody plants

Mosaic leafpattern

Crinkled leaves

Yellowed leaves

Plant stunting


Bioassay is a useful procedure for detection and identification of viruses and uses indicator plants which react to infection by showing characteristic symptoms. Over the last few decades, laboratory based virus test methods, such as Enzyme-Linked-Immuno-Sorbent Assay (ELISA) and Polymerase Chain Reaction (PCR), have been developed and are now being used routinely in many laboratories. Automation of these procedures enables a high throughput of samples and provides rapid results.

Plant disease diagnosis

Fungi, bacteria, virus, and phytoplasmas cause distinct types of symptoms in most host-pathogen interactions. However, there are some diseases which show similarity in symptoms, though they are induced by different groups of pathogens. It is often impossible to diagnose plant virus infections merely by observing host symptoms. This is not only because several viruses may induce similar symptoms in the same plant, but virus-like symptoms may also develop for physiological reasons. In addition, symptoms may be very slight and inconclusive, or plants may be infected symptomlessly.

Creative Diagnostics provides high quality plant pathogen antibodies and plant pathogen elisa kits for these bioassay laboratories. In many instances, the PCR and ELISA assay method remains an indispensable tool. Inoculations can be carried out rapidly with the possibility of detecting a wide range of viruses on a fairly small number of plant species.