How to sample for Plant Viruses


Plant virus diagnosis depends in large part upon how the samples are taken and the quality of the sample received. It is important to note that plant viruses exhibit many different symptoms or none at all. Hence sampling is critical to confirm and determine the presence of a virus. Some of the symptoms exhibited by viruses in plants include; deformation, striping, mottling, green & yellow veining, stunting, brown necrotic leaf patches, death.  Virus symptoms and nutrient deficiencies can often be confused.

Plant viruses usually move up the plant, they exist in cells and plant sap. Hence during sampling, the upper leaves should be sampled.  The virus load may be lower in the newly formed leaflets at the top of the plant.

Where to take the leaves from for virus testing

Additionally, plant viruses are easily spread mechanically hence care should be taken to avoid contamination.  Disinfection between samples is critical during sampling.  Use gloves, disinfect gloves with 20% skimmed milk, or a heavy bleach solution.

Sampling procedure

  1. Take a leaf or leaf-let (depending on the leaf types) from the recently emerged leaves (Usually second top most leaves).
  2.  If suspecting virus infection, take samples from those plants exhibiting symptoms.  If there are no symptoms / for screening,  do random sampling in a Zigzag pattern. Take as many leaves for one composite sample as possible to increase chances of picking the virus
  3. Place the sample in a well labelled bag. Plastic bags are usually the best due to limited contamination. The Cropnuts' sample bag is ideal for this work.
  4. NB: More leaves/ leaflets can be collected per variety or line from different plants to form a composite sample.
  5. For your own future reference please note the location of the sample – (Farm & field / or GPS reference)
  6.  Place the collected samples in a cool place and if possible at 4oC to avoid sample deterioration.  Do not freeze the sample!
  7. Ship to the lab immediately.
  • NB: For quick and best results; ship all virus samples to the lab earlier in the week (Monday-Wednesday).
  • Send the samples to CROPNUTS LAB, Limuru, with a sample submission form and LPO.

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