Abstract
In nature, a microbe tries an invasion to a plant by using every opportunity, but many plants can prevent an invasion as a non-host plant. However, in the case of plant disease, a plant is unable to prevent an infection causing growth inhibitions, then a relation of plant-plant pathogen occur, and various interactions are performed. Various chemical substances such as microbe-producing phytotoxins and plant-producing phytoalexins, incorporated in their interactions, have been elucidated. Investigation of quantitative/qualitative biological activities against man/animal of these chemical substances, and of accumulation situation are necessary, to circumvent the danger of becoming mycotoxin or mycotoxin mimic. If phytotoxins such as host-specific-toxins showed an important activity, their accumulation amount in resistance varieties/non-host plants/post-harvests should be investigated. Similar investigations are also required in the case of plant-protecting substances.
