Abstract

One of the most restricting macronutrients for crop yield worldwide is phosphorus, which is often less than 1% of the total amount contained in soils. To promote its bioavailability, there are microorganisms considered vital that can solubilize and mineralize their pools in soils. In the current study, we assessed the potential of phosphate-solubilizing bacteria (PSB), isolated from the olive tree rhizosphere grown on phosphate sludge, to solubilize phosphate, promote plant growth, and tolerate abiotic stresses. Based on 16S rRNA gene sequencing, twenty-four PSB strains were identified and retained for in vitro analysis. According to the results, all the strains were able to solubilize the Moroccan rock phosphate, with soluble phosphate concentrations ranged from 5.34 µg/mL to 227 µg/mL. Furthermore, the majority of the strains are thermo-tolerant and halotolerant. Nonetheless, only five strains produced indole acetic acid. Regarding biocontrol potentialities, several PSB strains were characterized by producing hydrogen cyanide and hydrolytic enzymes (cellulase, and chitinase), of which three strains identified as Pseudomonas moraviensis, Bacillus cereus, and Bacillus aryabhattai, with a remarkable multi-trait combination were selected for antagonism and co-inoculation tests. The findings revealed that these PSB strains significantly inhibited Fusarium oxysporum (17.65%–62.35%) and Verticillium dahliae (52.35%–66.87%) and promoted common bean growth. The consortium of the three strains showed the best results by significantly increasing both plant height and tap root length and dry biomass compared to individual inoculation. The PSB selected from the olive tree rhizosphere growing on phosphate sludge have the potential to be useful as biofertilizer and biocontrol agents for attaining sustainable food crop production.

摘要

磷是对全球作物产量影响最大的常量营养素之一，通常不到土壤中总含量的 1%。为了提高其生物利用度，有些微生物被认为是至关重要的，它们可以溶解和矿化土壤中的池。在当前的研究中，我们评估了从磷酸盐污泥上生长的橄榄树根际中分离出来的解磷细菌（PSB）溶解磷酸盐、促进植物生长和耐受非生物胁迫的潜力。基于16S rRNA基因测序，鉴定出24株PSB菌株并保留用于体外培养分析。结果表明，所有菌株均能够溶解摩洛哥磷矿，可溶性磷酸盐浓度范围为5.34 µg/mL至227 µg/mL。此外，大多数菌株具有耐热性和耐盐性。尽管如此，只有五株菌株产生吲哚乙酸。在生防潜力方面，一些PSB菌株具有产生氰化氢和水解酶（纤维素酶和几丁质酶）的特点，其中3株被鉴定为摩拉维假单胞菌（Pseudomonas moraviensis ） 、蜡状芽孢杆菌（Bacillus cereus）和雅氏芽孢杆菌（ Bacillus aryabhattai），具有显着的多性状组合，被选用于拮抗作用和联合接种试验。研究结果表明，这些 PSB 菌株显着抑制尖孢镰刀菌(17.65%–62.35%) 和大丽轮枝菌(52.35%–66.87%) 并促进菜豆生长。与单独接种相比，三个菌株的联合体显示出最佳结果，显着增加了植物高度、主根长度和干生物量。从磷酸盐污泥上生长的橄榄树根际中选择的 PSB 有潜力用作生物肥料和生物防治剂，以实现可持续粮食作物生产。