Effect of arbuscular mycorrhizal fungi inoculation on growth and physiology performance of olive trees under regulated deficit irrigation and partial rootzone drying

Abstract

Agriculture water resources are limited in several Mediterranean regions. In this context, the current study was conducted to examine the response of mychorrizal olive plants to two water-saving irrigation techniques, namely partial-root zone drying (PRD) and regulated deficit irrigation (RDI). Young olive (Olea europaea L., cv Picholine marocaine) trees were grown with (+AMF) or without (-AMF) Rhizophagus irregularis using a split-root experiment, which consists in dividing the root system of the plant in two parts placed in separate pots. The pots were exposed simultaneously to three different water regimes: Control, with both root compartments well irrigated; RDI, with both compartments irrigated (50% of the control); and PRD, with one compartment irrigated (50% of the control), while the other compartment was kept dry switching every 10 days. Stomatal conductance (gs), leaf relative water content (RWC), vegetative growth (shoot length, total leaf area and leaf number), proline and sugar contents and leaf carbon isotope discrimination (δ13C) were measured in order to evaluate the influence of arbuscular mycorrhizal (AM) symbiosis on the tolerance of the olive tree to water stress induced by RDI and PRD. The low soil moisture under this two water treatments have a negative effect on all studied parameters. However, the olive plants inoculated with the AM fungi (AMF) generally have significant great growth indices in comparison with the non-inoculated ones. Furthermore, at physiological (gs and RWC) and biochemical (proline, sugar and δ13C) level, +AMF olive plants exhibit better performance under drought than -AMF ones. These responses were mostly, earlier under PRD treatment. AM olive plants can tolerate better the water deficit stress of RDI and PRD treatments saving up to 50% of the irrigation water.