Diversity of root-knot nematodes in Moroccan olive nurseries and orchards: does Meloidogyne javanica disperse according to invasion processes?

Abstract

BackgroundRoot-knot nematodes (RKN) are major pest of olive tree (Olea europaea ssp. europaea), especially in nurseries and high-density orchards. Soil samples were collected from main olive growing areas of Morocco, to characterize Meloidogyne species and to discuss the contribution of biotic and abiotic factors in their spatial distribution.ResultsRKN were found in 159 soil samples out of 305 from nurseries (52.1% occurrence) and in 11 out of 49 soil samples from orchards (23.2% occurrence). Biochemical and molecular characterisation (PAGE esterase and SCAR) revealed the dominance of M. javanica both in nurseries and orchards with minor presence of M. incognita only in nurseries, and M. arenaria in only one nursery. RKN were distributed on aggregated basis. Frequent presence of M. javanica in orchards might have come from nurseries. In contrast, the detection of M. incognita in nurseries alone suggests that this species could not reproduce in orchards because of either the competition with other plant-parasitic nematodes or unfit local habitats. The impact of environmental variables (climate, habitat origin and physicochemical characteristics of the substrates) on the distribution of Meloidogyne species is also discussed.ConclusionOlive nurseries in Morocco are not able to guarantee the safety of rooted plants. As a result, olive production systems are exposed to strong RKN invasion risks. Consequently, the use of healthy substrates in nurseries may prevent plant-parasitic nematode induction in orchards.

Diversity of root-knot nematodes of the genus Meloidogyne Göeldi, 1892 (Nematoda: Meloidogynidae) associated with olive plants and environmental cues regarding their distribution in southern Spain

“…arenaria (2.7%)] [ 28 ] compared to our results in cultivated fields. Similar results were obtained between RKN species found in olive nurseries and their distribution in olive fields in Morocco [ 19 ]. Hamza et al .…”

“…One of the likely major sources of root-knot nematode inoculum in the field could be the use of infected rooted plantlets, as suggested by other authors [ 19 , 28 ]. In Spain, a study in olive nurseries reported higher percentages of root-knot nematodes in infected plantlets [ Meloidogyne incognita (14.7%), M .…”

“…Understanding the drivers of community structure, however, is an essential point for increasing our knowledge regarding ecological phenomena involved in RKN management. In this context, recent studies have been performed on cultivated olives with the aim of finding the important factors influencing RKN population dynamics [ 18 , 19 ]. Although both these studies suggested that the presence of RKN species could be determined by human activities (i.e.…”

“…Although both these studies suggested that the presence of RKN species could be determined by human activities (i.e. widespread introductions from nurseries), they also found habitat factors driving the distribution of RKNs among cultivated Moroccan olives [ 18 , 19 ]. Nonetheless a general pattern for statistically significant environmental factors affecting RKN distribution in olive plants is lacking for Spain, which furthermore differs somewhat from African environmental conditions.…”

Evaluation of the Phytopathological Reaction of Wild and Cultivated Olives as a Means of Finding Promising New Sources of Genetic Diversity for Resistance to Root-Knot Nematodes

“…Furthermore, the recent transition to intensive olive growing, with high-density planting, irrigation and substantial amounts of fertilizers, could increase the nematode population densities to further damaging levels. Based on confirmed levels of pathogenesis (Sasanelli, 2009) and frequent association with olive (Hamza et al 2017;Archidona-Yuste et al 2018), M. javanica was used as a standard species for the study. This species proved to be suitable to this role, and, following controlled inoculations, produced levels of infection readily measurable by root galling and nematode reproduction.…”