Use of mycorrhizal fungi as a strategy for improving the drought tolerance in date palm (Phoenix dactylifera)

•Indeginous and selected mycorrhizal fungi improve the drought tolerance in Phoenix dactylifera•The positif effect of mycorrhization on the soil’s water regime (75% or 25% of field capacity).•The levels of phenols, peroxidase and polyphenolxydases have increased by mycorrhization.

This study has highlighted the importance of both indeginous and selected mycorrhizal fungi in improving the tolerance of the date palm (Phoenix dactylifera) under water deficit. A fungal isolate from the palmeraie of Aoufous, Morocco, and three Glomus reference (monosporus, clarum and deserticola) were tested for their efficiency to infect and improve tolerance of date palm to water stress. After 36 weeks of plants mycorrhization, the used fungal isolates have proved infectious with a frequency of mycorrhization higher than 60% and an intensity of palm root colonization that decreases when the soil water deficiency increases. Based on water regime imposed on the soil (75% or 25% of field capacity), the effect of mycorrhization on the enhanced biomass production and improvement of minerals absorption of palm appeared well except in the case of inoculation with Glomus deserticola. The improvement of Aerial dry mass of mycorrhized seedlings by Aoufous complex and Glomus monosporus is 2.4 times more than non mycorrhized plants under the limiting conditions in water. The mycorrhized date palm trees by the same fungi maintain higher relative water content (RWC) and water potential than the control plants subjected to the limiting water condition (25% FC). Under this severe water treatment, the values of stomatal resistance remained significantly higher in non-mycorrhized plants (3.21) than in mycorrhized ones (2.13–2.51). Indigenous fungal isolates have proved to be as effective as the selected Glomus. G. deserticola was ineffective in improving the growth of date palms and was more affected by the drying of the soil. Moreover, the levels of phenols, the activities of both peroxidase and polyphenolxydases have significantly increased in the roots of mycorrhized and non-mycorrhized palms exposed to severe water stress. Overall, these levels are higher in mycorrhized palm than in the control palms. These enzymes involved in stimulation of early oxidative events of stressed plants differ in their intensity and depending on AV fungi tested.