Systemic Resistance to Fusarium Wilt in Tomato Induced by Phytopthora cryptogea

Under climate chamber conditions, suppression of tomato wilt disease caused by Fusarium oxysporum f. sp. lycopersici (FOL) was obtained by spraying a suspension of Phytophthora cryptogea (Pc) zoospores on the green parts of two tomato cultivars, Danish Export (suscept- ible) and Elin F1 (moderately resistant). Direct compet- itive or antagonistic interaction between Pc and FOL in the soil or on the root surfaces was ruled out, but not interaction within the stems of plants. After Pc applica- tion followed by FOL inoculation, the two cultivars showed no wilt disease symptoms during the 50 days following FOL inoculation, whereas the FOL-control plants were destroyed by wilt within about 40 days. Over a period of 7 weeks, both Pc and FOL were detected inside the stems of plants, for all treatments. Pc and FOL were also found inside the petioles of plants, except for one treatment, Pc application followed by challenge inoculation with FOL. Systemic induced resistance was assumed to be responsible for the observed elimination of disease incidence. It was concluded that, under climate chamber conditions, Pc application to the green parts of tomato plants is a viable alternative for control of disease incidence caused by FOL.