Diversity of plant-parasitic nematode communities associated with olive nurseries in Morocco: Origin and environmental impacts

Abstract

Plant-parasitic nematodes (PPN) are key impediments to efficient global crop production and impair the quality of susceptible plants in nurseries as well. In this context, nematode communities were determined in 305 solid substrate samples collected from 25 olive (Olea. europaea. subsp. europaea) nurseries in Morocco. Taxonomical and functional diversity as well as the structures of PPN communities were described and then compared between regions, cultivars as well as according to biotic and abiotic factors. A high diversity of PPN was observed, with the detection of 63 species and 26 genera. The most dominant taxa detected were spiral nematodes (Helicotylenchus spp. and Rotylenchus spp.), stunt nematodes (Tylenchorhynchus spp.), grazer nematodes (Tylenchus spp.) and root-knot nematodes (Meloidogyne spp.). Hoplolaimidae nematodes (Helicotylenchus spp. and Rotylenchus spp.) and Tylenchus spp. were better adapted to rainy conditions that prevailed in the northern regions of Morocco. Multiblock analyses demonstrated that functional diversity (cp and trophic groups) was more affected by the environment than taxonomical diversity (total number, species richness, locale diversity and evenness). They also indicated that PPN communities were more impacted by climatic variables (rainfall and minimum temperature) and nursery substrate origins than by soil physic-chemical factors. Nevertheless, a co-inertia analysis showed that N, P and K amendments in olive nurseries enhanced the development of harmful PPN, especially root-knot nematodes.