Isolation and characterization of rhizosphere bacteria with potential to improve the plant growth of banana plants in Juja, Kenya

Abstract

Banana (Musa spp.) is the world’s third most important starchy food. It is widely grown in developing countries and requires large amounts of nitrogen fertilizers which are expensive to the poor resource farmers and may be hazardous to the environment. Phosphorus is another mineral nutrient which is essential for plant development and growth but it is usually unavailable to the plant due to its insolubility. Plant growth promoting rhizobacteria are found in the rhizosphere in association with roots and can enhance the growth of the plant. This study isolated rhizobacteria associated with bananas (Musa spp.) from rhizosphere soil samples collected from seven banana farms in Juja, Kenya and evaluated their potential as biofertilizers. Out of the 20 bacterial isolates obtained, nitrogenase activity was recorded in 19 isolates and 18 isolates solubilized phosphates. Phylogenetic analysis clustered the isolates into three phyla represented by six different genera; Pseudomonas, Bacillus, Staphylobacterium, Chryseobacterium, Streptomyces and Paenibacillus. The Bacillus and Pseudomonas spp. isolates recorded the highest phosphorus solubilization of 1.6 and 1.5 on the phosphate solubilization index. There was significant differences in the plantlet’s mean height (p<0.0001) and mean mass in dry weight (p<0.0006) in all the five strains tested as compared to the control. Bacillus megaterium (KP797917) and Streptomyces sp.(KP797931) bacterial strains isolated from banana rhizosphere in Juja, Kenya had a significant difference in mean number of green leaves (p=0.000) as compared to the control. Plantlets treated with Streptomyces sp. registered a significantly higher growth in all parameters (p<0.05). The intake of zinc and iron was not influenced by inoculants (banana plantlets growth with the five bacterial isolates). The study showed that certain banana rhizosphere bacterial isolates such as Streptomyces sp. and Bacillus megaterium have plant growth promoting traits that could be utilized as biofertilizers in agriculture in the production of bananas.