Plant-parasitic Nematodes Associated with Olive Tree in Southern Morocco

Abstract

Plant-parasitic nematodes affect significantly the production of susceptible plants, including olive trees. In this context, nematode communities were determined in soil samples collected from 23 olive growing sites in the Haouz and Souss regions (southern Morocco). These sites corresponded to various modalities: wild (Olea europaea L. ssp. sylvestris) or cropped olive (Olea. europaea L. ssp. europaea), traditional or high-density cropping, rainfed or irrigated. Even free-living nematodes prevailed in most of the sites, high population levels of plant-parasitic nematodes were observed in rainfed cropping systems than in irrigated systems. Ten nematode families and 14 genera were identified. The most important plant-parasitic nematodes detected, in order decreasing frequency of infestation (percentage of samples), were spiral nematodes Helicotylenchus spp. (100%) and Rotylenchus spp. (87%), lesion nematodes Pratylenchus spp. (100%) and root-knot nematodes Meloidogyne spp. (40%). Most of the nematode species were assigned to more or less colonizer nematodes, whereas only one family (Longidoridae) was assigned to persistent nematodes. Considering the two producing areas, plant-parasitic nematodes were significantly more abundant in the Souss region than in the Haouz region, but nematode diversity was higher in the second one. The prevalence of Meloidogyne spp. in the Haouz region would be related to the predominance of irrigated cropping systems in this region. Hoplolaimidae nematodes (Helicotylenchus spp. and Rotylenchus spp.) are better adapted to rainfed conditions that prevail in the Souss region. Co-inertia analysis showed the importance of soil physic-chemical characteristics (e.g., pH, texture and nutrients) on the structure of the plant-parasitic nematode community patterns. The high occurrence of Helicotylenchus spp. in olive orchards may be induced by fertilization. Aphelenchoides spp., Gracilacus spp., Pratylenchus spp., Rotylenchidae and Tylenchidae were supported by coarse textures as it was observed in the Souss region.

How anthropogenic changes may affect soil-borne parasite diversity? Plant-parasitic nematode communities associated with olive trees in Morocco as a case study

“…These conditions induce favourable environments for PPN multiplication, especially irrigation, which enhances the development of roots [ 14 ]. This was consistent with others observations in southern Morocco [ 59 ]. This could explain the high abundance of colonizer species and, consequently, the high pathogenicity (PPI value) of the communities recorded in these cropping conditions.…”

Plant-parasitic nematodes parasitizing saffron in Morocco: Structuring drivers and biological risk identification

“…Relationships between the distribution of PPN genera and soil physico-chemical factors were highlighted. The most dominant genera in Taliouine and Taznakht regionss were positively correlated with loamy and clay soils, in agreement with previous studies (Salahi et al, 2014;Aït-Hamza et al, 2015;Aït Hamza et al, 2018). High abundances of PPNs were observed in loamy soils whilst clay soils exhibited low PPN abundances.…”

Diversity and Management Strategies of Plant Parasitic Nematodes in Moroccan Organic Farming and Their Relationship with Soil Physico-Chemical Properties

“…Similarly, clay, sand, and silt contents were significantly (P < 0.05) associated with the PPN communities in this study and could separately define PPN population structures [74,75]. Previous studies [76][77][78] revealed the same results with loamy and clay soils. The sand content effect on PPN occurrence on organic crops is due, probably, to its irreversible impact on soil temperature and pH as well.…”