Arbuscular mycorrhizal fungi associated with Citrus sinensis L. in relation to soil physicochemical properties in Tunisian citrus orchards

The relationships between arbuscular mycorrhizal fungi (AMF) development levels and soil physicochemical properties remain poorly known in citrus. In our study, rhizospheric soil and root samples of Maltaise sanguine blood orange (Citrus sinensis) have been collected from thirteen representative sites in the Cape region in the Northeastern part of Tunisia. Soil physicochemical properties, spore density (SD), AM colonization rate, and the contents of easily extractable glomalin-related soil protein (EE-GRSP) and total glomalin-related soil protein (T-GRSP) were determined in the rhizosphere soils. The results indicated that SD, the frequency of mycorrhizal colonization, and T-GRSP concentration were significantly different among the study sites. Pearson correlation analysis showed that SD was negatively correlated with T-GRSP and available phosphorus. The frequency of mycorrhizal colonization was positively correlated with soil pH. The intensity of mycorrhizal colonization was negatively correlated with the soil concentration of exchangeable Na while arbuscules abundance was positively correlated with soil-available phosphorus. T-GRSP was positively correlated with available phosphorus, soil organic matter, and total nitrogen while negatively correlated with soil pH. The obtained results demonstrated that soil physicochemical properties are important in determining AMF development in Maltaise citrus orchards.