Diversity of Phosphorus-Solubilizing Microbes Isolated From Different Cropping Systems of Zimbabwe for Use as...

Soil phosphorus deficiency and the high cost of mineral fertilizers necessitate research into alternative strategies. Inoculating seeds with adapted phosphorus-solubilizing microorganisms (PSMs) could be a cost-effective option. This study explored diversity, including phenotypic and genotypic characteristics of PSMs from selected soils and cropping systems of Zimbabwe, for coapplication with rock phosphate (RP). Culturable PSMs were isolated from preincubated or cowpea rhizosphere soil. Over 91% of the 37 isolates (PSM1-PSM37) were bacteria, while 8% were fungi. Diversity was higher in Dorowa (H' 2.99; DMn 8.49) than that in Marondera (H' 2.85; DMn 7.57), and under groundnut and maize (H' 3.26) than other crops. Some PSMs occurred only in Marondera (8%) and Dorowa (14%). The P solubilization index on RP-amended Pikovskaya medium, ranged between 1.00 and 15.9. Sixty-five percent of the best 28 isolates were Gram-negative cocci or bacilli, while 35% were Gram-positive cocci. A dendrogram based on morphological, biochemical, and functional characterization grouped the isolates into two major clusters and four subgroups. On the basis of 16S recombinant DNA analyses, the Bacillus genus predominated (61%), with the highest P solubilization capacity (Bacillus amyloliquefaciens), while the rest (39%) were Enterobacter, Microbacterium, Paenibacillus, Klebsiella, Priestia, Acinetobacter, Nocardioides, and Kocuria genera. In conclusion, studied soils harbor diverse PSMs that solubilize RP, indicating their potential to develop affordable bioinoculants for improved productivity on P-limited soils. The study pioneers the discovery of diverse PSMs native to Zimbabwean soils. Further studies are required to evaluate PSM-RP efficacy with various crops under glasshouse and field conditions and benchmark with conventional fertilizers.