ABSTRACT
Disease diagnosis is very important for developing effective strategies for disease management. Without diagnosis, there can be no disease management. Crop disease diagnosis is an art as well as a science (Holmes et al., 2000). The diagnostic process involves the recognition of symptoms (which are associated with disease) and signs (which are not outwardly observable) and requires intuitive judgment as well as the use of scientific methods. Several conventional techniques are followed to diagnose disease incidence. These techniques include visual inspection and recognition of symptoms and isolation and examination of crop pathogens using microscopy. Such techniques are time-consuming and may not be able to detect latent infections. Several diagnostic assays have been developed for early and rapid diagnosis. These include immunoassays, nucleic acid probe-based methods, and PCR-based techniques. The use of these techniques in the diagnosis of fungal, bacterial, viral, viroid, and phytoplasma diseases is described here.
