Screening of endophytic plant growth-promoting bacteria isolated from two Nigerian rice varieties.

Abstract

Probiotic bacteria, inhabiting the endosphere of plants, presents a major opportunity to develop cheap and eco-friendly alternatives to synthetic agrochemicals. Using standard microbiological procedures, culturable bacteria were isolated from the endosphere (root, stem and leaf) of two Nigerian rice varieties (Ofada and ITA 150). Assays including indole acetic acid (IAA) production, phosphate solubilization, seed germination assay, hydrogen cyanide (HCN) and ammonia production, and antifungal assay were conducted to identify the phytobeneficial bacterial strains. A total of 193 bacteria were isolated from all samples. The roots had the highest bacterial count of 45 and 61 x 10⁸ cfu/g in Ofada and ITA 150 respectively when compared with the stem and leaf samples. The bacterial genera isolated were Bacillus, Pseudomonas, Enterobacter, Klebsiella, Staphylococcus, Citrobacter and Escherichia. Eight isolates produced IAA as well as ammonia. Phosphate solubilization was observed in five isolates while four isolates produced HCN. The germination rate of rice seeds coated with bacterial isolates ranged from 81.48% to 100%. Eight bacterial isolates inhibited the growth of Fusarium oxysporum and Rhizoctonia solani, but Citrobacter freundii and Enterobacter cloacae showed the highest antagonism. Thus, eight bacteria isolates showed multiple beneficial abilities and may be considered as promising microbial inoculants for rice plant growth and productivity.

Keywords: Bacteria, endosphere, plant growth, rice