Influence of mycorrhizal inoculation on the salt tolerance of hybrid artichoke seedlings

In the Mediterranean region many horticultural crops as well as artichoke have to cope with increasing salinization of irrigation water. Arbuscular mycorrhizal fungi (AMF) are known to improve plant tolerance to salt stress in some crops. In this study, the role of mycorrhizal symbiosis in the alleviation of salinity stress induced by sodium chloride (NaCl) in three hybrid artichokes, Madrigal F1, Opal F1 and Concerto F1 (Nuhems company), was examined. The root systems of 2- month-old artichoke plantlets, with or without mycorrhizal fungus (Glomus viscosum), were placed in distilled water enriched with different salt concentrations (0, 50, 100, 150, 200 mM NaCl) to study the wilting response. To study the wilting trend, a visual rating system was developed defining the following wilting indexes: T0, no wilting; T1, foliar damage on less than 50% of vegetal tissues of oldest leaves; T2, initial wilting and foliar damage on more than 50% of vegetal tissues of oldest leaves; T3, foliar damage on youngest leaves; T4, total wilting. The required time to reach different wilting indexes was monitored both for mycorrhizal and not-mycorrhizal plants. Electrolyte leakage by leaves was assessed 28 hours after stress imposition to estimate the extent of cell damage induced by salt. Electrolyte leakage was performed on young and old leaves to evaluate the different foliar damage that visual analysis showed. The mycorrhizal symbiosis improves tolerance to salt stress in all hybrid artichoke seedlings tested. However the results show a different sensitivity among Madrigal F1, Opal F1 and Concerto F1. The greatest tolerance observed in inoculated plants could be in agreement with the improvement of growth stimulated by mycorrhizal symbiosis, which lead to the resulting dilution of toxic ions.