A preliminary comparative study of root – associated microbial communities in plantain (Musa paradisiaca L.) grown in natural and herbicide polluted soils in Toru Orua, Bayelsa State

This preliminary comparative study was conducted to assess the impact of herbicides on the microbial communities of plantain (Musa paradisiaca L.). Rhizospheric samples were collected from natural and herbicide polluted soils within the campus of the University of Africa, Toru-Orua, Bayelsa State, Nigeria. Samples were serial diluted where 10-6 and 10-7 were adopted. Microbial populations in both herbicide polluted soil (HP) and Normal Soil (NS) were carefully compared on PDA, MAC and NA media and morphological characteristics differences were carefully analysed. The results revealed clear differences between HP soil and NS. The HP soil sample had a significantly higher overall microbial load and species richness compared to the NS sample. Total culturable bacteria in HP soil made up 43.75% of the isolates while NS soil had 25%. In HP soil, fungi constituted 25% of the isolates while only 6.25% fungi were found in NS soil. key organisms isolated include Cryptococcus spp. and Fusarium spp. (pathogenic) were more in occurrence than other commensal fungi such as Rhizopus spp., Basidiomycetes, Aspergillus spp. where Basidiomycetes which are known decomposers. Bacterial isolates are Micrococcus luteus (mostly abundant) Enterobacter spp, Enterobacter aerogenes, Bacillus spp., Proteus spp. and Pseudomonas spp. While studies have reported a decline in overall microbial presence and diversity after herbicide use due to general toxicity, the increased abundance and richness in the HP soil reflects an ecological trend of selective adaptation as previously reported by a few authors. The study concludes that the use of herbicides as effective weed control, compromises the microbial balance of the plantain's rhizosphere. Thus, herbicide application does not directly destroy the plant microbiome but creates an imbalance that lead to the elimination of organisms which are not tolerant and the subsequent selective promotion of herbicide degrading microorganisms.