Investigation of plant growth promoting properties of microorganisms obtained from various sources

This thesis aimed to determine the plant growth-promoting properties of isolated bacteria from various environmental sources. The obtained isolates were tested for nitrogen fixation, phosphate solubilization, production of indole-3-acetic acid (IAA), 5-Aminolevulinic acid (ALA), siderophore, hydrogen cyanide (HCN), exopolysaccharide (EPS), 1-Aminocyclopropane-1-Carboxylic Acid (ACC) deaminase, chitinase, protease and cellulase. According to the results of each test, the isolates showing the highest values were selected, and 16S rRNA sequence analyses were performed. According to this, the isolates were PB4 Stenotrophomonas rhizophila, PB25 Stenotrophomonas maltophilia, PB41 Serratia liquefaciens, PB47 Bacillus pumilus, PB71 Enterobacter sp, PB72 Enterobacter ludwigii, PB77 Raoultella sp., PB136 Bacillus cereus, PB89, PB90, PB122 and PB182 Pseudomonas sp., PB146, PB148 and PB149 Citrobacter freundii. PB149 isolate gave the best result in nitrogen fixation at 13.82 mg/L. PB25 was the best isolate in IAA production by 44.37 μg/mL. Activity measurements based on zone diameter, best isolates in phosphate solubilization, chitinase, protease, cellulase, ALA, ACC-deaminase, siderophore, HCN, and EPS production were determined as PB148, PB136, PB4, PB122, PB90, PB47, PB4, PB136, PB89, PB90, and PB77. In addition, PB25, PB41, PB72, PB89, PB90, PB122, PB136, and PB182 isolates showed antagonistic effects against Phytophthora infestans, Botrytis cinerea, and Monilinia laxa species which are the plant pathogens. KEYWORDS : Plant growth promoting bacteria, Nitrogen fixation, Phosphate solubilization, Phytohormone, Antagonism