Phosphorus (P) is one of the major bioelements limiting agricultural production. Phosphate solubilizing fungi play a noteworthy role in increasing the bioavailability of soil phosphates for plants. The present study was aimed at isolating and characterizing phosphate solubilizing fungi from different rhizospheres using both solid and liquid Pikovskaya (PVK) medium. A total of 359 fungal isolates were obtained from 150 rhizosphere soil samples of haricot bean, faba bean, cabbage, tomato, and sugarcane. Among the isolates, 167 (46.52%) solubilized inorganic phosphate. The isolated phosphate solubilizing fungi belonged to genera of Aspergillus (55.69%), Penicillium spp. (23.35%), and Fusarium (9.58%). Solubilization index (SI) ranged from 1.10 to 3.05. Isolates designated as JUHbF95 (Aspergillus sp.) and JUFbF59 (Penicillium sp.) solubilized maximum amount of P 728.77 μg·mL−1 and 514.44 μg mL−1, respectively, from TCP (tricalcium phosphate) after 15 days of incubation. The highest (363 μg mL−1) soluble-P was released from RP with the inoculation of JUHbF95 in the PVK broth after 10 days of incubation. The present study indicated the presence of diverse plant associated P-solubilizing fungi that may serve as potential biofertilizers.

BackgroundCaylusea absyssinica, a plant used as vegetable and for medicinal purposes was selected for in vitro antibacterial evaluation in this study. The main aim of this study was to isolate compounds from the plant roots and evaluate their antibacterial activities on clinical bacterial test strains.MethodsCompounds from roots of Caylusea absyssinica (fresen) were identified based on observed spectral (1H-NMR, 13C-NMR and IR) data and physical properties (melting point) as well as reported literature. Disk diffusion method was employed to evaluate the antibacterial activities of the isolated compounds on four test bacterial strains namely, Staphylococcus aureus (ATCC25903), Escherichia coli (ATCC25722), Pseudomonas aeruginosa (DSMZ1117) and Salmonella thyphimurium (ATCC13311).ResultsTwo compounds, CA1 and CA2 were isolated from the methanol crude extract of the roots of Caylusea absyssinica (fresen). The compounds were identified as β-sitosterol and stigmasterol, respectively. Evaluation of antibacterial activities revealed that the compounds are active against all the bacterial strains in the experiment, showing inhibition zones ranging from 12 mm-15 mm by CA1 and 11 mm-18 mm by CA2 against the different test strains. However, the compounds were less active than the reference drug (Gentamycine), which showed minimum inhibition zone of 21 mm (Pseudomonas aeruginosa) and maximum of 28 mm (Escherichia coli) inhibition zone.Discussion and conclusionThe isolation of the compounds is the first report from roots of Caylusea abyssinica and could be potential candidates for future antibacterial drug development programs.Electronic supplementary materialThe online version of this article (doi:10.1186/s12941-015-0072-6) contains supplementary material, which is available to authorized users.

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Haricot bean (Phaseolus vulgaris L.) is one of the most important cash crops and export commodities besides its use in human food and soil fertility improvement. Phosphorus (P) is one of the major bio-elements that limits agricultural production. However, phosphate-solubilizing fungi play a noteworthy role in increasing the bioavailability of soil phosphates for plants. The purpose of this study was to evaluate the effects phosphate solubilizing fungi on the growth of haricot bean plants. Cultural and morphological features were used to tentatively identify the fungal isolates to genus level. Based In vitro phosphate solubilization efficieny conducted in both solid and liquid PVK medium following standard procedures, two best isolates were selected and evaluated under greenhouse for their performance on haricot bean. Under greenhouse experiment, shoot height (47.31 cm plant ), P content (0.59%) and N content (1.96%) were significantly increased by co-inoculation of two isolates (PSFAP) in the soil amended with rock phosphate (RP) compared to control. Moreover, the highest number of leaves (59.55 leaves plant -1 ) and root fresh weight (14.19 g plant -1 ) were recorded as a result of inoculation with isolate PSFP compared to control. The present study indicated the presence of potential plant associated fungi that possess phytobeneficial traits for extending their use as microbial biofertilizers after testing their suitability for the desired purpose.

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