The phosphate-solubilising ability of Penicilium guanacastense and its effects on the growth of Pinus massoniana in phosphate limiting conditions.

Microbes in soil can degrade insoluble inorganic and organic phosphorus, which are components of the soil phosphorus cycle and play an important role in plant growth. Pinus massoniana is a pioneer tree species used for afforestation in southern China and grows in poor, acidic soil. A shortage of available phosphorus in soil limits the growth of Pmassoniana To alleviate this situation, it is necessary to improve soil fertility. A fungal strain (JP-NJ2) with the ability to solubilize phosphate was isolated from the Pmassoniana rhizosphere. The ability of JP-NJ2 to solubilize inorganic and organic phosphorus and promote the growth of Pmassoniana was evaluated. It showed that JP-NJ2 could grow in NBRIP inorganic phosphate (AlPO₄, FePO₄·4H₂O, and Ca₃[PO₄]₂) fermentation broths, with the highest phosphorus concentration (1.93 mg/mL) and phosphate-solubilizing rate (43.7%) for AlPO₄ and in Monkina organic phosphate fermentation broth with a phosphorus concentration of 0.153 mg/mL. The phosphate-solubilizing capability in inorganic and organic fermentation broths was negatively correlated with pH. JP-NJ2-produced acids at a total concentration of 4.7 g/L, which included gluconic (2.3 g/L), oxalic (1.1 g/L), lactic (0.7 g/L), and malonic (0.5 g/L) acids. It prioritized extracellular acidic phosphatase and combined with phytase to solubilize organic phosphates. The fungal suspension and extracellular metabolites from phosphate-solubilizing fungi promoted the shoot length of Pmassoniana seedlings by 97.7% and 59.5%, respectively, while increased the root crown diameter by 46.8% and 27.7%. JP-NJ2 was identified as Penicillium guanacastense based on its morphology and phylogenetic analyses of five genes/regions (ITS, ben A, cmd, cox1, and tef). This is the first report on Pguanacastense isolated from pine tree rhizosphere soil in China and its high phosphate-solubilization capability, which promoted the growth of PmassonianaPguanacastense JP-NJ2 has potential use as a biological fertilizer in forestry and farming.