Bacterial Abundance under Soil Rhizosphere of Drought Tolerant Tree Species in Sudan Savannah Ecozone of Northern Nigeria

The rhizosphere soil has a high potential for natural resources and contains many microorganisms that remain unexplored in the Sudan Savannah Ecozone. This study aimed to assess the bacterial abundance in the rhizosphere soil of drought-tolerant tree species in the Sudan Savannah ecozone of Northern Nigeria. Pour plate techniques were used to evaluate the bacterial abundance in the rhizosphere of drought-tolerant tree species. Bacterial colonies were isolated using nutrient agar medium and identified using macroscopic and microscopic characteristics of the bacteria. Bacterial count increased from 1.3 x 106 to 5.08 x 106 CFU/g at the depth of 0 – 30cm for soil under Pakia biglobosa (P. biglobosa) and Balanite aegyptiaca (B. aegyptiaca) respectively. Whereas at the depth of 30 – 60 cm 1.62 x 106 and 9.37 x 105 CFU/g were recorded in soils under B. aegyptiaca and A. digitata respectively. Under the B. aegyptiaca rhizosphere, the dominant bacterial species at 0-30 cm included Bacillus cereus, Bacillus mycolides, Aeromonas veronii, and Staphylococcus prophyticus. At the deeper 30-60 cm, Bacillus coagulans, Bacillus mycolides, Bacillus subtilis, and Aeromonas hydrophila were isolated. The A. digitata rhizosphere showed a presence of Staphylococcus prophyticus, Micrococcus luteus, Bacillus mycolides, Pseudomonas syringae, and Bacillus megaterium. Also P. biglobosa rhizosphere, Bacillus papilliae, Bacillus megaterium, and Aeromonas veronii were identified at 0-30 cm. At 30-60 cm, the bacterial community shifted to include Bacillus subtilis, Bacillus megaterium, and Aeromonas hydrophila. Hence, bacterial counts were consistently higher under rhizosphere of drought tolerant tree species at the shallower 0-30 cm depth compared to the deeper 30-60 cm depth in the Sudan Savannah Ecozone of Northern Nigeria. It is recommended that indigenous drought tolerant tree species should be protected to avoid their extinction from the Sudan Savannah ecozone there by preventing the soil microflora.