Arbuscular mycorrhizal fungi associated with Phoenix dactylifera L. grown in Tunisian Sahara oases of different salinity levels

Abstract

Soil salinity continuously threatens the sustainability of several economically strategic crop production systems in Tunisia, especially in the arid and Saharan areas. In addition, it also affects microbial populations associated with the roots of crop plants, which are known to contribute efficiently to crop’s productivity and adaptation to environmental stresses. In this respect, the effect of soil salinity on arbuscular mycorrhizal fungi (AMF) associated with date palm (Phoenix dactylifera L.), the flagship crop of Tunisian oases, is still rarely studied. The present work is the first investigation of the colonization of date palm roots by AMF and the production of easily-extractable glomalin related soil protein (EE-GRSP) in different date palm plantations where soils present high salinity rates up to 7.6 dS m−1. The results revealed a negative correlation between soil salinity and the intensity of mycorrhization on one hand but a positive correlation between soil salinity and EE-GRSP and spore density on the other hand. This suggests that the production of EE-GRSP might be involved in the tolerance of AMF to elevated salinity in the soil. In addition, four AMF species, identified based on spore morphology and molecular phylogenetic analyses, have been recovered in single spore derived cultures, namely Albahypha drummondii, Dominikia disticha, Funneliformis coronatus and Rhizoglomus irregulare. The investigation of the current mycorrhizal status of date palm roots and rhizosphere soil EE-GRSP concentrations along a salinity gradient on one side and isolation and identification of AMF strains native to Tunisian oases ecosystems one the other represent first steps towards the development of sustainable agricultural practices in this region where salinity is the main production-limiting factor.