This work was aimed to select the proper Arbuscular Mycorrhizal (AM) inocula strain to enhance the growth of squash plants in calcareous P-deficient soil. Three treatments of phosphorus fertilizer of calcium triple phosphate, 15.5% P2O5 were tested at different rates. In parallel, pots were inoculated with 4 AM strains (Rhizoglomus irregulare) namely M49; M139; M301 and M 510. Treatments were repeated 5 times and arranged in the greenhouse in a randomized completely block design (RCBD) and plants were harvested after 57 days. In conclusion, from the results and under the same conditions of this experiment, we recommended that all mycorrhizal strains were effective in improving plant growth. The strain M301 enhanced squash plants growth and P uptake. Also, inoculation with this strain could improve P availability in soil. The two mycorrhizal strains (M49 and M139) can be used for improving the growth of squash plants under low P level and in calcareous soil conditions. This study is one of the few studies that indicate the specialization of mycorrhizal fungi strains on the host plant and this study must be followed by many other studies in different climatic conditions, different soil properties and on different genus and strains of AM fungi on different plants family to confirm or deny this hypothesis.