Isolation and characterization of bacterial root endophytes from Kenyan basmati rice with potential to enhance plant growth

Abstract

Rice is an important food crop. Its grain serves as a staple food for a large part of the world's human population especially in urban areas. An endophyte is an endosymbiont, often a bacterium or fungus, that lives within a plant for at least part of its life without causing apparent disease. In this study, a survey of bacterial root endophytes was carried out. 73 bacterial pure isolates were obtained from the root samples collected from farmers’ and research fields in Mwea and Ahero. They were morphologically characterized and screened for biological activities. The biochemical tests were used to characterize all the isolates. 10 isolates produced indoleacetic acid (IAA) implying potential to enhance plant growth. 67 isolates were positive for phosphate solubilisation. These 73 isolates were further grouped according to morphological and biochemical similarity and 37 were selected for molecular characterization. All the 37 selected isolates were confirmed to have the potential to fix nitrogen based on acetylene reduction assay (ARA). The phylogenetic analysis of 28 potential isolates clustered them into four different genera namely Pseudomonas, Bacillus, Enterobacter, and Micrococcus. Results of the phylogenetic analysis of the potential isolates were supported by the outcome on morphological and biochemical characteristics. Isolates M31 and M32 obtained from Mwea Basmati 370 rice were shown to promote plant growth. Endophytes are useful in agriculture for enhancement of growth and production which would consequently enhance affordable production of Kenyan basmati rice. This will not only eradicate poverty and increase food security, but also help conserve microbial diversity.