Molecular Diagnosis of Plant Viruses

Makkouk, K.M. and S.G. Kumari. 2006. Molecular Diagnosis of Plant Viruses. Arab J. Pl. Prot. 24: 135-138. Proper virus identification is always the key in developing appropriate practical solutions to manage plant virus diseases. Recent advances in biotechnology and molecular biology have played a significant role in the development of rapid, specific and sensitive diagnostic tests. The use of ELISA, by employing either polyclonal or monoclonal antibodies, was a significant step in adding sensitivity and precision to virus detection. The development of the tissue-blot immunoassay (TBIA), as a variant of ELISA, greatly simplified testing, reduced the cost and permitted virus testing at locations where facilities are limited or even absent. Immuno Chromatographic Assay (ICA), is another ELISA variant which added speed to virus identification, where results can be obtained within 10-15 minutes, as compared to 2-3 hours for TBIA. However, ICA is more expensive than TBIA. The development of nucleic acid-based tools was another new dimension of virus detection. The most common among these techniques are cDNA hybridization and polymerase chain reaction (PCR). In addition, PCR can be used as a confirmatory test for TBIA, where processed blots can be cut individually and tested by PCR. This proved to work well with both DNA and RNA plant viruses. Furthermore, unprocessed plant tissue blots on nitrocellulose membrane represent a good sample for PCR amplification. PCR products can also be used for cloning and subsequent sequencing which is extremely useful for identification of new viruses or virus strains.