Diversity of plant-parasitic nematode communities infesting olive orchards in Tunisia in relation to agronomic factors

Tunisian olive cultivation constitutes one of the principal economical and agricultural strategic sectors. In order to increase olive production, the olive management systems are changing towards intensification with irrigation, the introduction of new varieties, the use of intercropping, and high inputs of pesticides and fertilizers. These practices may create an environment more favorable to soil borne pathogens and plant-parasitic nematodes. Therefore, this study was performed to explore for the first time the plant-parasitic nematodes infesting olive roots and their diversity in the main producing areas of olive in Tunisia including 123 olive orchards. It aims also to determine which agronomic factors influence the multiplication and the diversity of plant-parasitic nematode communities. These investigations identified 11 genera of plant-parasitic nematodes viz. Criconemoides spp., Helicotylenchus spp., Heterodera spp., Meloidogyne spp., Paratylenchus spp., Pratylenchus spp., Rotylenchulus spp., Rotylenchus spp., Tylenchorhynchus spp., Tylenchus spp., and Zygotylenchus spp. It is revealed that the intensification of olive orchards with irrigation and the association of intercrops are the main agronomic factors influencing the multiplication and the diversity of plant-parasitic nematodes infecting olive trees. In particular, olive orchards under super-intensive regimes are more conducive to the multiplication of Pratylenchus spp. while the presence of irrigated intercrops enhances the multiplication of Meloidogyne spp.. Therefore, for the establishment of new olive orchards, it is suggested to choose certified olive plants and avoid infested soils or intercrops that can host dangerous nematodes.