Interactions between mineral fertilization and arbuscular mycorrhizal fungi improve nursery growth and drought tolerance of Prosopis alba seedlings

Prosopis alba Griseb. (algarrobo blanco) is an important tree legume in semiarid regions of South America. Under field conditions, their seedlings are subjected to a wide range of environmental conditions that might produce stress, reducing their survival and/or growth. The aim of this work was to evaluate the combined effect of two native arbuscular mycorrhizal fungi (AMF) inocula and fertilization on growth variables of P. alba seedlings under nursery conditions and after drought stress. P. alba seedlings received different levels of basic fertilization (0%, 25% and 100%) and were inoculated with native AMF isolated from different rainfall regions of Parque Chaqueño Argentino: Colonia Benítez (CB, 1300 mm rainfall) and Padre Lozano (PL, 650 mm rainfall) or a mixture of both inocula (MIX), while the control group remained uninoculated. The combined application of native AMF and fertilization did not affect mycorrhizal colonization but allowed the formation of the different AMF structures. Moreover, when comparing the PL inoculum from a low rainfall region with other treatments, it significantly increased growth and development under nursery conditions and drought stress tolerance in the greenhouse. Therefore, AMF benefits for P. alba were related to inoculum source, being improved by the application of low fertilizer rates. This work supports the development of sustainable P. alba seedlings production and their field establishment under symbiotic conditions with native AMF.