Identification of culturable bacteria associated with the rhizosphere of Lablab purpureus growing in Namibia

Abstract

Abstract Dolichos lablab ( Lablab purpureus (L.) Sweet)) is a multipurpose drought tolerant protein-rich legume crop native to Africa and grown in warm temperate to tropical climates for its edible seeds and manure. Lablab purpureus holds significant benefits to subsistence farmers and offers a great promise for sustainable crop productivity, especially in marginalised areas. Its uses range from human consumption as a vegetable to improving soil fertility, and as forage. Notwithstanding Lablab purpureus crucial potential functions in Namibia, there is currently limited information regarding the plant’s rhizosphere bacteria. The study aimed at identifying Lablab purpureus’ natural rhizosphere bacteria. Isolation of rhizosphere bacteria involved the use of general media (Luria Bertani agar and tryptic soy agar); selective media such as Rhizobium and Yeast Extract Mannitol (YEM) Congo red from soil sample extracts. Eighty-five strains of bacteria were isolated and were subsequently identified by 16S rRNA gene sequencing analysis. The results showed that they belonged to the following genera, Bacillus, Streptomyces, Exiguobacterium, Stutzerimonas, Rhizobium, Acidovorax, Agrobacterium, Psychrobacter, Priestia, Planococcus, Bhargavaea, Stenotrophomonas, Caulobacter, Peribacillus, Niallia, Athrobacter, Sphingobium, Enterobacter, Sphingobacterium, Sinorhizobium, Flavobacterium, Microbacterium, Metabacillus, Neobacillus , and Pseudomonas which are reported to have growth promoting substances. The study highlighted the potential use of these plant growth promoting rhizobacteria for inocula production or biofertilisers for enhancing growth and nutrient content of beans and other crops under field conditions. The study was the first report of Lablab purpureus’s rhizosphere associated bacteria in Namibia.