PGP Activities of Halophilic and Thermophilic Actinobacteria Derived From AlgerianEcosystem and Inoculation Effects on Triticum durum

Abstract

under rainfed conditions, on the high plateaus, where drought represents a major limitation to crop production. Yield gap between irrigated and rainfed trials indicated that gain yield reduction owing to water deficit ranged from 24 to 80%, depending on rainfall amount and dis­tribution patterns. In addition, salinity stress, which in­duces both ionic, osmotic and oxidative damages, impairs plant growth and causes severe reductions in cropyield. To achieve the salt tolerance, damages must be firstly prohibited or all eviated; secondly, homeostatic conditions should be recovered in the new stressful con­dition; and finally, the growth must restart, although at al ower rate. The use of efficient micro-organisms like plant growth-pro-moting rhizobacteria (PGPR) is helpful in boosting and improving sustainable agriculture and environmen­tal stability. Currently, soil salinity is one of the major concerns in agriculture that limits water absorption and induces ac­cumulation of toxic ions in the different plants’ organs. The application of halotolerant and ther­mophilic plant-growth- promoting (PGPB) actinobacteria can be a valid tool to reduce the harmful effects of saline stress and to improve crop productivity. PGPR can promote growth via different mechanisms including phytohormones production (e.g. auxin, cytoki­nin, ethylene and gibberellins), nitrogen fixation, nutri­ent mobilization and siderophore production. PGPR can induce salinity stress tolerance through the modulation of physiological and biochemical process. They can also induce systemic resistance. The aim of the present work was to select actinomycete strains with plant-growth-promoting capacities, and to de­termine their effects on the growth of Triticum durum. Actinomycete isolates were firstly screened through sever­al in vitro plant-growth-promoting (PGP) traits (i.e., phos­phate solubilization ability, production of indole-3-acetic acid, hydrocyanic acid, and ammonia, nitrogen fixation, growth at different temperatures and NaCl concentra­tion, antifungal activities and several enzymatic activities). Strains with interesting traits were investigated for their biostimulant effects on Triticum durum.