A Study of the Interaction Effect of Verticillium Wilt Verticillium dahliae and Root-knot Nematode Meloidogyne javanica (in Two Sets of Pots Beds) on Olive Seedlings

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Verticillium wilt Verticillium dahliae is now a days commonplace in olive orchards in north of Iran. Root-knot nematode, Meloidogyne javanica, as well is one of the most widely disseminated plant parasitic nematodes in olive orchards of Iran. This study was arranged to find the effects of two sets of pot beds on these pathogens' interaction. Microsclerotia of Verticillium dahliae and J2s of Meloidogyne javanica were employed as the source of inoculum for the experiment. One-year-old seedlings of olive cultivar, Zard, were transplanted to the different sets of pot beds containing 720 cm3 of sterilized sandy loam soil (sand: 72.8%, silt: 13.8%, clay: 13.4%, organic substance: 2.2%, ECE = 2.76 ds/m, pH = 7.76) vs gravel (particle diameter: 5-7mm). The experiment was conducted in a completely randomized design of eight replications: Treatments were: control, nematode alone, fungus alone, nematode and fungus (simultaneously), nematode and fungus (concomitantly, fungus two weeks prior to nematode), nematode and fungus (concomitantly, nematode two weeks prior to fungus). Pots were inoculated with 1500 J2s of nematode and/or 7200 microsclerotia according to the treatment. The experiment was terminated after a lapse of nine months. Results showed that fungus colonization in root was more in seedlings transplanted into sandy loam soil, but female population as well as knots in the root system were higher in pots filled with gravel than in the sandy loam soil. The number of plant chlorotic, necrotic and wilt leaves was more in plants grown in sandy loam soil. In any case, variance within the pots containing sandy loam soil vs gravel was not different (P?0.05). Presence of nematode prior to fungus causes reduction in colonization of the fungus in the root and stem and inversely the presence of fungus prior to nematode caused reduction in number of galls produced by the nematode (P?0.05). Severe symptoms on aerial parts of the plants were observed when both pathogens were inoculated simultaneously (in the sandy loam soil, 97%) (P?0.05).

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