Relationships between plant parasitic nematodes and Verticillium dahliae on olive

Abstract

The relationships between the plant parasitic nematodes Meloidogyne incognita and Pratylenchus vublUS and the fungus Verticillium dahliae were studied on the two olive cultivars Leccino and Pendolino. One year old rooted cuttings were planted in July 1998 in 1.2 I clay pots filled with steamed sandy soil. For each cultivar there were uninoculated plants, which served as control, plants inoculated only with M. incognita (4,000 eggs/pot), P. vulnus (200 nematodes/pot) or V dahliae (50 ml!pot of a suspension at a concentration of 4x107 conidia/m!), plants inoculated with either nematode species plus the fungus, and plants inoculated with all three pathogens. Eighteen months after fungus inoculation, when the test was discontinued, plant growth parameters were determined together with vascular discoloration, root gall index and nematode reproduction rate. All plants inoculated with 17 dahliae either as a single pathogen or in combination with nematodes consistently showed wilting and vascular discoloration. Plants of the cv. Pendolino inoculated Simultaneously with the three pathogens exhibited significantly higher wilt severity after six months, but not after 18 months. Olive growth was suppressed by all pathogens when were inoculated singly or in combination. However, the combined inoculation of olive with V dahliae and nematodes did not result in additional growth suppression. Root growth of olive was statistically suppressed by V. dahliae, but not by either of the nematode species. Reproduction of M. incognita was reduced on cv. Leccino by the simultaneous presence of P. vulnus and on cv. Pendolino by the simultaneous presence of P. vulnus or V dahliae alone or in combination. The reproduction of P. vulnus was suppressed by all pathogen combinations on cv. Leccino and only by the simultaneous presence with M. incognita on cv. Pendolino.