Optimal environmental conditions for production of plant growth regulators by rizobacteria

ABSTRACT

This study was carried out to isolate and identify some plant growth promoting rhizobacteria [PGPR]. The optimum incubation condition, i.e. temperature and fermentation period, for plant growth regulators [PGRs] production were limited. Obtained data revealed that rhizosphere of cereal crops showed higher PGPR isolates compared to rhizosphere of other crops. Among the examined isolates, fifteen were highly efficient for auxins production. The most potent isolates for indoles production were chosen and these isolates were identified as Azotobacter chroococcum [R19] and Bacillus megaterium var, phosphaticum [R44]. The optimum incubation temperature for highest production of auxins, gibberellic acid [GA[3]] and cytokinins were 32 and 30°C for A. chroococcum and B. megaterium var. phosphaticum, respectively. In addition, the highest production of these phytohormones were obtained by the two strains after four and two days fermentation period, respectively