A Study of the Interaction of Root-Knot Nematode Meloidogyne javanica and Wilt Agent Verticillium dahliae on Seedlings of some Olive Cultivars

In the course of the present study, samples were taken from the non-defoliant strain of Verticillium dahliae (SS-4) from infected olive groves in Toshan area in Southern Gorgan. Root-knot nematode, Meloidogyne javanica, was recovered from infested olive seedlings and after identification was reaned on tomato seedlings cv. Rutgers. During the study, one-year-old seedlings of olive cultivars Zard, Roghani, Koroneiki (resistant to verticilliosis) vs. Manzanilla (sensitive to verticilliosis), were transplanted to pots containing 2000g of sterilized sandy loam soil. The experimental study was conducted in a completely randomized design of 32 treatments and five replications. Treatments consisted of: control, mere nematode, fungus alone, and fungus + nematode. Pots were inoculated with (2000, 3000, 4000) J2 of the nematode and/or (10 no/g soil) microsclerotia of fungus as according to the treatments. Pots were placed on glasshouse benches at a temperature of 25-27°C and in natural light. The experiment was terminated after 10 months past with the following parameters determined: fresh weight of root and stem, no. of galls and egg masses per each root system, percentage of incidence of symptom on aerial parts, browning of vascular tissue, decrease in seedling height and stem/root tissue colonization by the fungus. Results indicated that presence of nematode caused reduction in colonization of the fungus in the root and stem and vice versa, meaning that presence of fungus caused reduction in no. of galls and egg masses produced by the nematode. This was when a maximum percentage of disease symptoms on aerial parts was observed in fungus + nematode treatments. Severe fungal wilt on aerial parts of Zard cultivar was observed in fungus + nematode treatments and mild fungus wilt was observed in mere fungus treatments and in the case of Koroneiki cultivar. The reduction of gall and egg mass production in root system occurred respectively in cvs. Manzanilla, Zard, Roghani and Koroneiki cultivars (p?0.05).