Symbiotic efficiency and infectivity of an autochthonous arbuscular mycorrhizal Glomus sp from saline soils and Glomus deserticola under salinity

The purpose of this study was to compare the effect of salinity on the symbiotic efficiencies and mycelial infectivity of two arbuscular mycorrhizal fungi (AMF), one isolated from saline soils (Glomus sp.) and the other (Glomus deserticola) from nonsaline soils (belonging to the Estacion Experimental del Zaidin collection). Lettuce plants inoculated with either of these two fungi or maintained as uninoculated controls were grown in soil with three salt concentrations (0.25, 0.50 or 0.75 g NaCl kg(-1) dry soil). Both AMF protected host plants against salinity. However, when the results of shoot dry weight and nutrient contents were expressed relative to the total length of mycorrhiza formed, it was found that both AMF differed in their symbiotic efficiencies. These differences were more evident at the two highest salt levels. Glomus sp.-colonized plants grew less and accumulated less N and P, whereas they formed a higher amount of mycorrhiza. The mechanism by which Glomus sp. protected plants from the detrimental effects of salt was based on the stimulation of root development, while the effects of G. deserticola were based on improved plant nutrition. The increase in salinity of soil decreased the hyphal growth and/or viability of Glomus sp. to a higher extent than those of G. deserticola since the mycelial network generated by G. deserticola was more infective than that of Glomus sp.