Rapid methods for diagnosis of soil‐borne plant pathogens

. Root diseases are often hard to identify or quantify visually, particularly by the inexperienced, so several modern methods of diagnosis from other branches of biology have been modified for soil‐borne plant pathogens. Though very sensitive, most of these techniques are slower and more laborious than the routine inspection of plants for disease symptoms, yet they need less expertise and are consistently accurate. Apart from immunology, most laboratory diagnostic procedures have so far proved ill‐suited for field use, as they are neither sufficiently flexible nor portable. Despite the rapid detection and identification of numerous viruses by routine enzyme‐linked immunosorbent assays (ELISA), there have been until recently few suitable protocols adapted for fungi. DNA hybridization forms the basis of another group of fairly rapid diagnostic techniques which will probably be restricted to the laboratory for some while yet. Nevertheless, DNA techniques have proved valuable in various investigations, such as unravelling the phylogeny of some species of soil‐borne pathogens. For the foreseeable future methods based on antibodies and DNA probes are likely to extend their domination of detection and diagnosis techniques. By making recognition easier, these techniques play complementary roles in expanding our understanding of the biology, taxonomy and ecology of soil‐borne pathogens.