Abstract
Many plant pathogens are host-selective, and specificity between varieties is often observed among cultured plants. In a few cases, the cause of the specificity is attributable to the toxins produced by pathogens, which are called host-specific toxins in these cases. So far, 13 microbes are known to produce 15 host-specific toxins, and 8 of them have their structures elucidated. Recent revelation by the studies we have been concerned with, that HMT- toxins, produced by H. maydis, race T, have structures analogous to PM-toxins produced by P. maydis, a microbe alien to H. maydis, gave stimulus to the re-recognition of importance of these toxins as pathotoxins, that are the conceived ultimate causal agents of plant diseases. Studies on structure-activity relationships and active molecular sites in progress, aided by synthetic chemical techniques. The chemical and biological aspects of these host-specific toxins are reviewed, including the results of our recent studies on ACRL-toxins, which are produced by 1 of 3 varieties of A. citri, which are specifically pathogenic to different citrus varieties.
