Effect of symbiotic association of rhizobia and endomycorrhizae from Moroccan arid littoral dunes on Acacia cyanophylla tolerance to drought

Abstract

Abstract. Hatimi A, Tahrouch S, Bouizgarne B. 2018. Effect of symbiotic association of rhizobia and endomycorrhizae from Moroccan arid littoral dunes on Acacia cyanophylla tolerance to drought. Asian J For 2: 39-45. Coastal sand dunes in arid region serve as habitat of coastal biotas including rhizobia and mycorrhiza. This research aimed to investigate the effect of selected symbiotic rhizobia native from coastal dunes of Souss-Massa, Morocco, alone or in association with endomycorrhiza to improve the tolerance of Acacia cyanophylla plants to drought stress. A symbiotic indigenous endomycorrhizal fungi M, and three rhizobia isolates (i.e., two slow-growing isolates R1 (Bradyrhizobium sp. RCM6), and R2 (Bradyrhizobium sp. RLC3) and a fast-growing isolates R3 (Rhizobium sp. S21)) were inoculated to A. cyanophylla under drought stress conditions in greenhouse. Results showed that the growth and nutrition of seedlings of A. cyanophylla were drastically affected after two months in drought stress conditions. However, inoculation of the symbiotic microorganisms either alone (treatments M, RMC6, R2 or R3) or as inoculums consisting of combination of the rhizobia with the endomycorrhiza (treatments MR1, MR2 or MR3) resulted in enhanced tolerance of A. cyanophylla seedlings to drought stress. At 100% of field capacity (fc), all treatments showed a significant improvement of plant growth compared to non-inoculated plants in stress conditions. In addition, Bradyrhizobium RCM6 (R1) holds a high efficiency to improve the growth and nutrition of the host plant. Indeed, higher number of nodules/plant and higher amount of total nitrogen were recorded in the seedlings inoculated with Bradyrhizobium sp. RCM6 in comparison with plants inoculated with the two other rhizobia Bradyrhizobium sp. RLC3 (R2) and Rhizobium sp. S21 (R3), and control plants. Dual inoculation with each of the three rhizobia and the endomycorrhizal complex (M) led to higher water content (WC) and relative water content (RWC) and a significant increase in Phosphorus content of the aerial part. While positive effects were recorded for Phosphorus, no such effects were recorded for nitrogen. However, the overall results showed the importance of the use of microorganisms in the dune coastal environment particularly adequate tripartite association: rhizobia Endomycorrhizes-A. cyanophylla in enhancing tolerance to drought stress.