Estimating the contribution of arbuscular mycorrhizal fungi to drought tolerance of potted olive trees (Olea europaea)

The aim of the present study is to investigate the contribution of mycorrhization to the resilience of olive trees to drought. One-year-old olive plants were inoculated (Myc(+)) or not (Myc(-)) with arbuscular mycorrhizal fungi (AMF), and subjected to a 40-day-drought period. At regular intervals of the watering-off period and after rehydration period, water relations and gas exchanges parameters were measured. Similarly, the total soluble sugars, proline, and mineral nutrients concentrations were determined. The results revealed that Myc(+) plants were less affected by drought than Myc(-) plants proving the involvement of the AMF in the alleviation of drought impact on olive tree. In fact, the turgor potential (psi(p)) in Myc(+) plants exhibited positive values during the whole treatment period, while psi(p) in Myc(-) plants was negative mainly under severe stress intensity. Moreover, the stomatal function of Myc(+) plants was less affected by drought compared to Myc(-) plants. The maximum of mycorrhizas relative drought alleviation rate (RDAR) was estimated to be 40% for psi(pd) and RWC, 36% for the osmotic potential (psi(S)), 86% for psi(p), 16% for g(s), and 27% for E. The osmotic adjustment by proline was earlier in Myc(+) plants than in Myc(-) ones. The inoculation with AMF also improved mineral uptake (K, N, Zn, and Fe). After 40 days of drought, Myc(+) plants survive but not Myc(-) ones. In addition, the restoration of the irrigation permitted the Myc(+) plants to recuperate from severe drought stress. To sum up, inoculation of young olive trees with the AMF improved their resilience to drought.