Isolation of Phosphate-Solubilizing Bacteria from Oat Rhizosphere

Rhizosphere samples were collected from two different sites in the northwest of Morocco (33°32′ 00″N, 7°35′00″W) in November 2018. In each field, five different oat plants were randomly selected for sampling, collected and stored at 4°C before analysis (Romano et al., 2020 (link)). The main physical and chemical properties of the rhizosphere samples are summarized in Table 1. For bacterial isolation, 10 g of the samples was shaken for 30 min in 90 ml of quarter strength Ringer’s solution (Oxoid, Milan, Italy) containing tetrasodium pyrophosphate (16% w/v) as previously described (Ventorino et al., 2014 (link)). Dilutions were performed from each sample followed by streaking in modified Pikovskaya’s (MPVK) without yeast extract (Nautiyal, 1999 (link)) and containing CaHPO₄ as the only inorganic phosphate source. After incubation for 7 days at 30°C, colonies distinguished based on phenotypic features such as morphology and biochemical characteristics (Gram reaction and catalase activity) were picked from plates and purified by repetitive streaking on plate count agar (PCA, Oxoid). The isolates obtained were stored at 4°C as slant cultures for further analysis.