Study of some growth promotion properties of bacterial isolates from animal manures and Identification selected isolates

Study of some growth promotion properties of bacterial isolates from animal manures and identification of selected isolates


Abstract
Background and objectives: Plants growth in agricultural soils are affected by several biological factors. Plant growth promoting bacteria can improve growth and yield of agronomic plants through direct and indirect mechanisms. Minimizing consequences of using high amount fertilizers and obtaining sustained level is the aims sustainable agriculture. Using of microorganisms due to improving soil fertility and nutrients uptake, lead to increasing growth and yield of plants and ameliorate soil health. The aim of this research was to isolation and purification of bacterial isolates from animal manures, evaluation of their plant growth promotion characteristics and identification of selected isolates.
Material and methods: In order to characterization of growth promotion characteristics of bacteria in this study, 10 samples of animal manures from different regions were collected. 27 isolates based on halo production, growth rate and morphological characteristics in NBRIP medium were purified and then and their typical PGP including auxin, Siderophore, HCN production, insoluble phosphates solubilization and secretion of protease, Cellulase, α-amylase and phytase were evaluated and finally selected isolates based on 16SrRNA were identified.
Results: Among all of the isolates, maximum phosphorous from tri-calcium phosphate (373 mg/l) and aluminum phosphate (13.3 mg/l) was released by isolates NO. 7. Significant negative correlation (r= -0.86, P≤ 0.01)between maximum solubilization of tri-calcium phosphate and pH was observed. Isolate NO.21 produced greatest amount of auxin (52.8 mg/l). Only isolates NO. 30 and 53 were positive in HCN production. Among 27 isolates only three of them had the ability to secret protease, cellulase and α-amylase. The utmost halo was measured by isolate NO.49 in production of these three enzymes. Evaluation of extracellular phytase production showed that only 6 isolates capable to produce the enzyme. The analysis of the 16S rRNA of the selected isolates showed highly similarity to bacteria belonging to the genera Enterobacter, Sphingobium, Serratia. Only one of the three selected isolates produced weak halo in CAS-agar medium and another two isolates didn't show the siderophore prodction capability.
Conclusion: Plant growth promotion characteristics of bacterial isolates, in this research, showed that some of the isolates had the potential to use as PGPB. Those isolates capable of producing protease, amylase and cellulase enzymes not only have usability in agriculture but also because of the importance of this group of enzymes, especially protease and amylase in industry, can also be considered.

Keywords: tri-calcium phosphate, aluminum phosphate, auxin, phytase, plant growth promotion