Effects of plant growth promoting bacterial isolates from Kavango on the vegetative growth of Sorghum bicolor

Sorghum is an important cereal that is processed into a variety of foods and leisure beverages across the African continent. Low sorghum yields experienced in agriculture is a result of major production constraints such as soil nutrient deficiency and plant disease. It is important that the methods for crop production are of a sustainable nature as the chemical fertilizers in current use are detrimental to the natural environment. The aim of this study was to determine the effects of plant growth promoting (PGP) bacteria on growth of Sorghum bicolor. PGP bacteria isolated from the rhizosphere of Pennisetum glaucum (Pseudomonas stutzeri ACM2-32, Kosakonia cloacae FCM2-50, Bacillus subtilis ASM1-59 and Bacillus amyloliquefaciens LSM1-61) and S. bicolor (Stenotrophomonas maltophilia LCS2-11) plants in Kavango (Namibia), were used as peat-based inoculants to evaluate their effects on the growth of S. bicolor. The combination treatment T9 (B. amyloliquefaciens LSM1-61: K. cloacae FCM2-50: P. stutzeri ACM2-32) significantly (p = 0.032) enhanced the biomass of S. bicolor as compared to the water control. Single inoculants consisting of S. maltophilia LCS2-11, K. cloacae FCM2-50 and B. amyloliquefaciens LSM1-61 and combination inoculants T7, T8 and T9, enhanced S. bicolor root biomass as much as a commercial fertilizer control. These results indicate that the plant growth promoting bacteria induced a beneficial effect on growth of sorghum seedlings. The future work involves testing these promising inoculants on growth of these sorghum plants to maturity stage to determine effects on seed yield over three seasons in multi-location trials.