Influence of colonization by arbuscular mycorrhizal fungi on three strawberry cultivars under salty conditions

Plant adaptation to hyperosmotic environments is generally associated with reduced growth and ultimately yield loss, making farming difficult. The potential of mycorrhizal symbioses to alleviate salt stress has been documented and benefits to plant revealed to be specific and dependent to both plant cultivars and fungal strains.  A factorial greenhouse experiment was performed to determine the effects of three arbuscular mycorrhizal fungi (AMF) species (Funneliformis caledonius, F. mosseae and Rhizophagus irregularis) on three ‘day-neutral’ strawberry (Fragaria × ananassa Duch.) cultivars (‘Albion’, ‘Charlotte’ and ‘Seascape’), and a mixture of R. irregularis and F. mosseae on ‘Seascape’, under four salt conditions (0–200 mM NaCl).  The overall results showed that plant biomass decreased with increasing salinity.  The cultivars responded differently to both AMF and salinity, and ‘Seascape’ was more tolerant to salinity than the other cultivars.  AMF enhanced plant growth and improved salt tolerance by increasing the proportion of medium (0.5<ɸ≤1.5 mm) and coarse (ɸ>1.5 mm) diameter roots. The mixture of two AMF species increased root and shoot mass to a higher degree than each species alone at low salinity (0–50 mM) but reduced fruit quality.  At higher levels (100–200 mM), R. irregularis alleviated salt stress and improved fruit quality to a higher degree than the other AMF species.  Our results support the use of bio-inoculants in saline horticultural areas.  Because cultivars respond differently to fungal inoculants, and inoculants prefer specific environmental conditions, fungal inoculants need to be screened on a cultivar- and condition-specific basis.