Cultivation, identification, and application of arbuscular mycorrhizal fungi associated with date palm plants in Drâa-Tafilalet oasis

Abstract

Arbuscular mycorrhizal fungi (AMF) have been frequently reported as effective tools for alleviating environmental stresses and promoting plant growth and yield. In this study, we aimed to isolate, culture, and identify molecular and morphological AMF species associated with date palms and spontaneous plants present at eight sites in the arid agroecosystem of the Drâa-Tafilalet oasis of Morocco. We tested the capacity of AMF to colonize micropropagated date palm seedlings at their first acclimatization stage. Soil and root samples were collected to propagate indigenous AMF strains using trap culture techniques under greenhouse conditions and, at the same time, their root colonization potential was evaluated. We used freshly propagated spores to establish a collection of single spore-derived cultures. Morphological, microscopic, and molecular approaches were adopted to quantify AMF communities in the roots and rhizosphere and identify the recovered AMF species present at the eight sites. In an inoculation experiment, a micropropagated date palm was inoculated with a consortium of four cultured AMF strains, alone or in combination with synthetic fertilizer or compost. Our results showed that after two cycles of trap culturing, the frequency and intensity of AMF colonizing host plant roots significantly increased, exceeding 91% and 50%, respectively. Using three trap plant species and favorable growing conditions helped increase root colonization rates and AMF proliferation. AMF propagation resulted in the cultivation of 13 AMF strains. Molecular and morphological analyses revealed six different AMF species within our cultures: Pervetustus simplex, Claroideoglomus etunicatum, Albahypha drummondii, Septoglomus xanthium, Funneliformis mosseae, and Rhizoglomus irregulare. Results of the inoculation experiment revealed that root colonization was higher in treatments augmented with synthetic fertilizers than those supplemented with compost with 84.4% as against 46.7% and 26.1% as against 12.3%, respectively, for colonization frequency and intensity. In contrast, shoot length and stem diameter of date palms were significantly higher in treatments augmented with compost and AMF than that with synthetic fertilizers. Synthetic fertilizers might have been partially immobilized directly after application, limiting availability and resulting in lower growth performance of date palms. These findings indicated that date palm groves are a niche for efficient indigenous AMF strains that can colonize and enhance date palm growth at the early stages.