Isolation of phosphate-solubilizing rhizosphere fungi from jabon merah (Neolamarckia macrophylla) stand of Sidrap Provenance, South Sulawesi

Phosphate is an essential macro element that has a necessary function as a constituent of ATP and DNA in plants. However, the availability of dissolved phosphate in the soil is minimal because it tends to bind with soil minerals to form phosphate complexes. With rhizosphere fungi, the low available phosphate in the soil can be overcome. This study aimed to determine the character and potential of fungi capable of dissolving phosphate. The source of the isolates used was a collection of rhizosphere fungus isolates under the red jabon stand. Purification was carried out using the point method on PDA media. The phosphate dissolving ability test was done using the standard method using liquid pikovskaya media and then analyzed descriptively and quantitatively. Eighteen rhizosphere fungus isolates were observed, two of which could dissolve phosphate, respectively, obtained from isolates JCS16 with a concentration value of 10.48 ppm, JCS 13 with a concentration value of 10.06 ppm.

Root carbon interaction with soil minerals is dynamic, leaving a legacy of microbially-derived residues

Minerals preserve the oldest most persistent soil carbon, and mineral characteristics appear to play a critical role in the formation of soil organic matter (SOM) associations. To test the hypothesis that carbon source and soil microorganisms also influence mineral-SOM associations, we incubated permeable minerals bags in soil microcosms with and without plants, in a 13CO2 labeling chamber. Mineral bags contained quartz, ferrihydrite, kaolinite, or native soil minerals isolated via density separation. Using 13C-NMR, FTICR-MS, and lipidomics, we traced plant-derived carbon onto minerals harvested from microcosms at three plant growth stages, characterizing total carbon, 13C enrichment, and SOM chemistry. While C accumulation was rapid and mineral-dependent, the accumulated amount was not significantly affected by the presence of plant roots. However, the rhizosphere did shape the chemistry of mineral-associated SOM. Minerals incubated in the rhizosphere were associated with a more diverse array of compounds with different C functional groups (carbonyl, aromatics, carbohydrates, lipids) than minerals incubated in a bulk soil control. These diverse rhizosphere-derived compounds may represent a transient fraction of mineral SOM, rapidly exchanging with mineral surfaces. Our results also suggest that many of the lipids which persist on minerals are microbially-derived with a large fraction of fungal lipids.