Histochemistry of Foliage Diseases

Abstract

About 30 years ago, when Dufrenoy started histochemical studies on host-parasite interactions, very little was known concerning the substantial chemical activity of host and parasite. This line of study was followed by several plant pathologists, but they soon realized that the mere application of histochemical techniques was suggestive but not conclusive in elucidating the mechanism of resistance, or the establishment of parasitic relationship, Since then great efforts have been concentrated in the biochemical analyses of the pathogenic activity of parasites, defence reaction of hosts, and the metabolic changes in host-parasite complexes. To date, there is much knowledge concerning toxins, toxic enzymes of parasites, phytoalexins, phenolic compounds, and enzymes which take part in the defence reaction of hosts, and the metabolism occurring in the host-parasite complex of obligate parasitism. The working hypothesis, which was postulated on the knowledge obtained by chemical analyses, should be substantiated by histochemical studies on host-parasite interaction at the site of contact. Recent advances in histochemistry and autoradi-ography under the electron microscope, immunochemical techniques involving the fluorescent- and ferritin-conjugated antibody techniques, and immuno-electrophoresis may facilitate the study. Recent electron microscopic studies on obligate parasitism showed some possibility that the active secretion of RNA, carrying presumably the information of the parasite gene, and the active intake of protein from host cytoplasm take place in the host-parasite interface. If this is true, and if we can interpret the gene-for-gene interaction as protein-to-protein interaction, this may possibly be visualized by the application of immunochemical techniques to the infection site. There is a bibliography of 127 references.