INDUCED RESISTANCE IN TOMATO PLANTS AGAINST FUSARIUM-WILT INVOKED BY FUSARIUM-OXYSPORUM F SP DIANTHI

Tomato plants, susceptible to Fusarium oxysporum f. sp. lycopersici, were inoculated by immersing the roots in a conidial suspension of F. oxysporum f. sp. lycopersici race 1, F. oxysporum f. sp. dianthi race 2 or a mixture of both fungi. Plants inoculated with F. oxysporum f. sp. lycopersici showed disease symptoms after 2 weeks, whereas plants inoculated with F. oxysporum f. sp. dianthi or a mixture of both fungi remained symptomless for over 7 weeks, the duration of the experiment. In another experiment root systems of plants were split and each half was separately inoculated. One half was firstly inoculated with F. oxysporum f. sp. dianthi or treated with water, followed after a week by a second inoculation of the other half with F. oxysporum f. sp. lycopersici or by a water treatment. The disease symptoms in the half firstly inoculated with F. oxysporum f. sp. dianthi were significantly delayed, compared to plants of which that half had been treated with water. Because F. oxysporum f. sp. dianthi reduced disease symptoms caused by F. oxysporum f. sp. lycopersici without any direct interaction with this pathogen, it is concluded that F. oxysporum f. sp. dianthi is able to induce resistance against F. oxysporum f. sp. lycopersici in tomato plants.