Study of plant growth promoting rhizospheric microorganisms from black pepper piper nigrum l

Abstract

Black pepper is a climbing vine known for its pungent fruit used as a spice worldwide The native population of phosphate solubilizing microbes was studied from the rhizosphere of Piper nigrum L plants grown in the Western Ghats of Karnataka India A variety of phosphate solubilizing bacteria and fungi were isolated from the rhizosphere soil samples of P nigrum plants in Karnataka India Low phosphate solubility is one of the most important factors limiting the plant growth in Indian soils Many microorganisms can enhance phosphate solubility but little is known about the magnitude of their phosphorus solubilizing ability The native populations of phosphate solubilizing bacteria and fungi were studied in different rhizospheric soil samples obtained from betel vine plants Piper betel L in order to compare the results Phosphate solubilizing capacity of different isolates was studied on Pikovskaya s media The isolates were tested for their phosphate solubilizing capacity in vitro with three different phosphate sources tricalcium phosphate potassium dihydrogen phosphate KHP and rock phosphate in the concentrations of two point five g L mines one five point zero g L mines one and seven point five g L mines one The three sources of phosphates were solubilized by the isolates in varying proportions The dominant PSM flora obtained from the samples included Bacillus and Aspergillus The study showed that PSM utilised the three phosphate sources tricalcium phosphate potassium dihydrogen phosphate and rock phosphate with considerable variability The phosphatase activity of the isolates showed that the predominant microorganisms were Bacillus subtilis five point thirty three U m L mines one and Aspergillus eleven point five U mL mines one The predominant organisms were identified up to molecular level Six bacterial and fungal isolates were selected from the rhizosphere of black pepper Piper nigrum L plants and were tested in vitro for their plant growth promoting abilities in the soil The species of Aspergillus selected were tested for the siderophore production indole acetic acid production catalase enzyme activity and biological control of pathogens through antagonism Siderophore production was quantitatively assayed using Chrome azurol S agar and the broth media The catalase activity was estimated colorimetrically The ability of the species of Aspergillus to inhibit the growth of pathogens Fusarium equiseticus and Mucor sp was tested by dual culture technique The results indicated high degree of PGP ability in case of Aspergillus niger followed by A flavus str1 with respect to all parameters It is well documented from ancient times that the active principles present in several plants have been used as medicines for various diseases and microbial infections These plant products have crucial molecules that act against several pathogenic bacteria and fungi Black pepper is a common house hold spice the extracts of which have been extensively used in medicines by our ancestors in India Pepper contains a spicy compound that adds flavour and pungency to the foods The active principle was found to be a tangy substance called piperine Piperine is an alkaloid found naturally in plants belonging to the family Piperaceae and is known to have antimicrobial and anti oxidant properties Pepper extract was obtained with ninety five percentage ethanol The extract was purified with acetone and KOH The percentage of piperine in the extract was determined using high pressure liquid chromatography analysis The crude extract acetone extract and different concentrations of commercially available pepper oil were tested for their anti bacterial and anti fungal activities with several species of Aspergillus and bacterial isolates from the rhizosphere of pepper The acetone extract with ninety four percentage piperine showed better antimicrobial property The bacterial and fungal isolates tested showed varying degrees of sensitivity towards pepper oil pepper alcoholic extract and acetone extract of pepper A niger seventy eight point eight mm was completely inhibited with acetone extract while Bacillus subtilis forty six point one mm Bacillus sp forty four point seven mm and other bacterial species were significantly inhibited by the pepper extracts MIC of pepper extracts and was pepper oil resulted in a higher value for acetone extract indicating its efficiency as an antimicrobial agent Antioxidant activity of various pepper extracts showed variable results Antioxidant activity of pepper oil and extracts were determined by three different methods two two Diphenly one picry one hydrazyl DPPH superoxide dismutase scavenging and scavenging by nitric oxide Pepper ethanolic extract showed the greatest activity with DPPH method