Isolation and characterization of beneficial indigenous endophytic bacteria for plant growth promoting activity in Molelwane Farm, Mafikeng, South Africa

Abstract

Plant-associated bacteria that live inside plant tissues without causing any damage to plants are defined as endophytic bacteria. The present study was carried out to analyze the phenotypic and genotypic diversity of endophytic bacteria associated with Amaranthus hybridus, Solanum lycopersicum and Cucurbita maxima. A total of 50 bacteria were isolated from the roots of the plants. All the isolates were screened for morphological features (Gram reaction, pigmentation, odour, colour, motility and sharp). Isolates exhibiting difference in morphological features were selected for molecular identification. Eight isolates that exhibited differences in phenotypic aspect were subjected to partial 16S-rDNA gene sequencing using polymerase chain reaction (PCR) for phylogenetic analysis. Sequence analysis using Clustal-X version 1.83 software identified the following isolated bacteria: Stenotrophomonas maltophilia KC010525, Pseudomonas putida KC010526, P. putida KC010527, P. putida KC010528, S. maltophilia KC010529, Achromobacter xylosoxidans KC010530, A. xylosoxidans KC010531 and Achromobacte sp. KC010532. Further evaluation of the bacterial isolates for phosphate solubilization capacity, indole acetic acid (IAA), hydrogen cyanide (HCN) and ammonium gas production, showed all eight bacterial isolates were able to produce IAA (0.32-2.42 mg/mgl^-1). However, seven isolates excluding S. maltophilia KC010525 showed ability to produce ammonium. HCN was observed in six isolates: A. xylosoxidans KC010530, A. xylosoxidans KC010531, A. KC010532, P. putida KC010526, P. putida KC010527, and P. putida KC010528. When determining the phosphate solubilizing capacity, it was observed that seven solubilized insoluble phosphate in Pikovskya’s agar plates produced halo zones (1 to 4 mm). Seven tested bacteria were active against Fusarium oxysporum. Therefore, the results indicate that the bacteria isolates may be used as a promising microbial inoculant for plant growth and productivity.

Keywords: Plant growth promoting rhizobacteria (PGPR), 16S-rDNA sequencing, HCN production, indole acetic acid (IAA), phosphate solubilization, antifungal activity.

African Journal of Biotechnology Vol. 12(26), pp. 4105-4114