Effects of Rhizobacteria Inoculum and Metabolite Treatments on Germinability of Cowpea (Vigna unguiculata) Seeds

Abstract

The aim of this study was to assess the growth promotion potentials of inoculums and metabolites of previously isolated rhizosphere bacterial strains on cowpea (Vigna unguiculata) seeds under soil conditions. A total of 15 bacterial isolates that comprise of B. cereus (6), B. thuringiensis (1), S.liquifasciens (2), P.rettgeri (4), P.vermicola (2). were used for the study. Growth promotion was evaluated using two different treatments: seed treatment and soil drenching. For all the treatments, 10 seeds were withdrawn from each treatment type and planted in the transparent plastic soil pots and observed for 20 d with daily watering. Every 5 d, for the 20 d planting duration, percent germination, plant height and vigor index of the seeds in the respective treatments were estimated.In the respective treatments, plant height showed consistent increases with days of planting. This observation was irrespective of the inoculums or water control setups. In the inoculum-treated seeds, a general increase in plant height over time was observed, although significant improvements in germination and vigor index were largely limited to specific strains. For the metabolite treated seeds, no significant differences in growth were observed, when compared to control seeds, with some treatments even resulting in lower vigor indices and germination rates. Seed treatment with inoculums resulted in some notable increases in vigor indices, while soil drenching with inoculums and metabolites indicated potential for enhanced plant development, though with varying efficacy across different strains.In conclusion, while promising, the use of rhizosphere bacterial strains and their metabolites as growth promoters for cowpea requires further refinement and field validation to maximize their agronomic benefits and ensure consistent, reproducible outcomes.