Genetic diversity and population densities of endophytic Bacillus spp. in yam plants

Abstract

This study was conducted as a first step in exploiting endophytic bacteria to improve yam production. Little information is available on population densities and genetic diversity of endophytic bacteria in yam cultivated in tropical regions. This study demonstrated that higher densities of total endophytic bacteria and Bacillus occur in the interior of roots and decrease as the sampled plant organ departs from soil. Bacillus represents approximately 1% of the total bacterial endophytic population. Random Amplified Polymorphic DNA (RAPD) analyses performed with 88 randomly-selected Bacillus isolates resulted in 28 groups, and sequence analyses of the 16S region of the ribosomal DNA of 24 isolates representing all major RAPD groups revealed that they could be clustered in 2 clades: Bacillus cereus and B. pumilus. While B. cereus was able to colonize the entire plant, B. pumilus remained confined to the rhizophores. Further research should concentrate on the application of these isolates in biotechnological processes, such as biocontrol and yam growth promotion.