Abstract
Some plant-pathogenic microorganisms are known as causes of wilt symptom of plant. The main cause of wilt symptom was described as invasion of vessel elements by microorganisms and blocking water-flow. Phomopsis sclerotioides causes black root rot of cucurbitaceae with wilt symptom. To reveal the mechanism of wilt symptom production by this fungi, xylem sap of inoculated seedlings of cucumber was measured. Xylem sap of seedling indicating wilt symptoms was only 1/10 of non-inoculated plants at 21 days after inoculation. Xylem sap of inoculated seedlings without wilt symptoms was slightly decreased. Furthermore, the plant which grafted one shoot onto two root indicated no wilt symptoms while only one root was infected. But in the root tissue of infected plants, spread of mycelium was detected, but invasion xylem was not detected. This suggest that P. sclerotioides infection cause water flow disturbance in the root tissue by unknown mechanisms.
