Evidence of variability in the structure and recruitment of rhizospheric and endophytic bacterial communities associated with arable sweet sorghum (Sorghum bicolor (L) Moench)

Abstract

Sorghum is the second most cultivated crop in Africa and is a staple food source of many African communities. Exploiting the associated plant growth promoting bacteria (PGPB) has potential as an agricultural biotechnology strategy to enhance sorghum growth, yield and nutritional properties. Here we use Terminal-Restriction Fragment Length Polymorphism (TRFLP) and Denaturing Gradient Gel Electrophoresis (DGGE) to evaluate the factors that potentially shape rhizospheric and endophytic bacterial communities associated with sorghum farmed in South Africa. Microbial diversity was typically higher in the rhizosphere and rhizoplane compared to the endophytic zones (root, shoot and stem). Geographical location was one of the main drivers in describing microbial community assemblages found in rhizospheric and endophytic sorghum-linked niches. NO3-N, total nitrogen and pH were clearly identified as the main abiotic factors shaping sorghum-associated soil communities. Our results also suggest that specific bacterial taxa with potential N-fixing capacities (Acetobacter sp., Azospirillum sp., Pantoea sp., Bacillus sp. and cyanobacteria) are consistently detected in sorghum-created rhizospheric and endophytic environments, irrespective of environmental factor effects.