Abstract

Arbuscular mycorrhiza (AM) is the most abundant and important terrestrial symbiosis due to its role improving the absorption of water and nutrients and increasing the plant tolerance to biotic and abiotic stress. Here, we evaluated the effect of AM fungal inoculation on the growth of lettuce (Lactuca sativa) under salt stress. The assay was conducted under greenhouse conditions (21°C, 50-60% relative humidity, at day/night 16/8 h, respectively). A completely randomized factorial design was used with three inoculation levels: i) without inoculation, ii) inoculation with native AM consortium from saline soils of Tarapacá Region, and iii) inoculation with an isolate of Claroideoglomus claroideum. Agricultural soil from Camiña Valley was used as substrate (pH 7.7; MO 2.2%; 10 mM NaCl kg-1; CE 2.7 dS cm-1), diluted with sand at a ratio 1:1 v/v, and autoclaved at 121° C for 30 min. Three sodium chloride (NaCl) concentrations were applied trough the irrigation (0, 40 and 80 mM). A harvest at 45 days after seeding (5 plants per treatment) was performed. The production of shoot and root biomass, chlorophyll content, proline synthesis, root colonization and density of AM fungi spores and mycelium were determined. The results showed a higher AM colonization and density of mycelium in plants inoculated with C. claroideum compared with plants inoculated with the native AM consortium. An increase on the production of shoot and root biomass, chlorophyll content and proline in plants AM inoculated compared to uninoculated plants were detected. These effects were more evident in plants growing under 40 and 80 mM NaCl inoculated with C. claroideum. These results demonstrate a high adaption to salt stress induced by C. claroideum, which support its use as inoculant for the lettuce production in saline soils or those lettuce crops that use saline waters.