In the rhizosphere, plant growth is facilitated by plant-growth-promoting rhizobacteria (PGPR). PGPRs like Actinobacteria can increase level of phosphate available to plants through P solubilization or mineralization. In this study we evaluated the ability of nine Phosphate Solubilizing Actinobacteria (PSA) to release P from rock phosphate (RP) and to promote maize growth and yield under in vitro and greenhouse conditions. Plate bioassay and pots culture experiment were conducted to investigate the effects of these PSA on maize plants development. High reactive rock phosphate (BG4, from Gantour phosphate mine, Morocco) and triple superphosphate (TSP) from Morocco were used as positive controls. BG4, is a reactive RP directly used to increase the P status of soil according to the Office Chérifien des Phosphates (OCP). For the other treatments, plants were grown in soil amended with low reactive RP obtained from the Khouribga phosphate mine (Morocco) and inoculated with selected PSA strains. Our findings have indicated that, PSA inoculation resulted in increasing of the assessed growth parameters and nutrient content in maize seedlings. Four of the tested strains (BC3, BC10, BC11 and P18) showed high performance efficiency in RP-solubilization and improved plant P nutrition and growth under low-P conditions i.e. amended with low reactive RP. Furthermore, inoculation with these latter strains also showed an important production of acid and alkaline phosphatase in the rhizosphere of the maize. The relative agronomic effectiveness (RAE) index showed that BC3(Streptomyces griseorubens) and BC11 (Norcardiopsis alba) increased the yield by 135.33 and 126.91% over the positive controls BG4. These strains can be considered as the most efficient to use rock phosphate as a crude phosphate fertilizer. Overall, our results demonstrate that PSA could constitute a promising solution to valorize low reactive RP in agriculture. The 16 S rRNA gene sequencing and phylogenetic analysis identified these isolates belong to Streptomyces and Nocardiopsis genera.

在根际中，促进植物生长的根际细菌（PGPR）促进了植物的生长。PGPRs（如放线菌）可以通过P增溶或矿化增加植物可用的磷酸盐水平。在这项研究中，我们评估了9种磷酸盐增溶放线菌（PSA）从磷酸盐岩（RP）释放P并在体外和温室条件下促进玉米生长和产量的能力。进行平板生物测定和盆栽培养实验以研究这些PSA对玉米植物发育的影响。高活性磷酸盐岩（来自摩洛哥Gantour磷酸盐矿的BG4）和来自摩洛哥的三重过磷酸盐（TSP）用作阳性对照。BG4是一种反应性RP，根据OfficeChérifiendes Phosphates（OCP）的规定，可直接用于提高土壤的P状况。对于其他治疗，将植物种植在土壤中，该土壤用从Khouribga磷酸盐矿（摩洛哥）获得的低反应性RP改性，并接种了选定的PSA菌株。我们的发现表明，PSA接种导致玉米幼苗中评估的生长参数和养分含量增加。被测菌株中的四个（BC3，BC10，BC11和P18）在RP增溶方面表现出较高的效率，并在低磷条件下改善了植物P的营养和生长，即使用低反应性RP进行了改良。此外，用这些后代菌株接种也显示了在玉米的根际中重要的酸和碱性磷酸酶的产生。相对农艺学有效性（RAE）指数表明BC3（PSA接种导致玉米幼苗中评估的生长参数和养分含量增加。被测菌株中的四个（BC3，BC10，BC11和P18）在RP增溶方面表现出较高的效率，并在低磷条件下改善了植物P的营养和生长，即使用低反应性RP进行了改良。此外，用这些后代菌株接种也显示了在玉米的根际中重要的酸和碱性磷酸酶的产生。相对农艺学有效性（RAE）指数表明BC3（PSA接种导致玉米幼苗中评估的生长参数和养分含量增加。被测菌株中的四个（BC3，BC10，BC11和P18）在RP增溶方面表现出较高的效率，并在低磷条件下改善了植物P的营养和生长，即使用低反应性RP进行了改良。此外，用这些后代菌株接种也显示了在玉米的根际中重要的酸和碱性磷酸酶的产生。相对农艺学有效性（RAE）指数表明BC3（这些后代菌株的接种也显示了在玉米的根际中重要的酸和碱性磷酸酶的产生。相对农艺学有效性（RAE）指数表明BC3（这些后代菌株的接种也显示了在玉米的根际中重要的酸和碱性磷酸酶的产生。相对农艺学有效性（RAE）指数表明BC3（与阳性对照BG4相比，灰链霉菌（Streptomyces griseorubens）和BC11（Norcardiopsis alba）的收率提高了135.33和126.91％。这些菌株可以被认为是最有效的将磷酸盐岩用作粗磷酸盐肥料的方法。总体而言，我们的结果表明PSA可以成为增值农业中低反应性RP的有前途的解决方案。16 S rRNA基因测序和系统发育分析鉴定出这些分离株属于链霉菌和诺卡氏菌属。