CO-INOCULATION EFFECTS OF Rhizobium AND Bacillus species ON GROWTH OF BELL PEPPER (Capsicum annuum var. grossum) IN A SCREEN HOUSE

Abstract

ABSTRACT The persistent use of agrochemicals for red pepper cultivation in Nigeria raises concern about environmental contamination andhuman health hazards which requires the development of an alternative strategy to increase food production. The rhizosphere bacteria may provide direct or indirect plant growth stimulus. This research dealt with the co-inoculation of the Bell pepper (Capsicum annuum var. grossum) at the screen house using the Rhizobium and Bacillus species. The Bacillus species were isolated in the Rhizosphere of the Capsicum annuum var.grossum plants, identified and screened to fit plant growth promotion characteristics whereas the Rhizobium was procured through International Institute of Tropical Agriculture Ibadan and identified through biochemical test. The Bacillus isolates having more capability of growth promotion were investigated following the 16SrRNA Sequencing method and were adopted to In-vitro seedling bio-assays and screenhouse trials. C. annuum var. grossum seeds were obtained at National Centre for Genetic Resources and Biotechnology and sterilized. The In-vitro germination assay was conducted using potential plant growth-promoting Bacillus isolates and Rhizobium followed by screen house experiments which was conducted in Federal University of Agriculture, Abeokuta. Each experiment was performed in a Completely Randomized Design with six treatments (no Bacillus, B. licheniformis,B. subtilis, Rhizobium, B.licheniformis +Rhizobium andB.subtilis +Rhizobium) in triplicates. Data on agronomic traits were collected and analyzed using One-way analysis of variance. The in-vitro germination assay revealed that inoculation of C.annuumvar.grossum seeds with Rhizobium and Bacillus strains resulted in 20 % to 33.3 % germination increase and vigour index of 18.30 - 105.0 % over un-inoculated seeds.The screen house growth experiment showed a significant enhancement(p ≤ 0.05) in the growth attributes(plant height,stem girth, number of branches, number of leaves and leaf length) with bacterial inoculation using the soil inoculation and seed treatment methods.The growth attribute of the inoculated plants using the soil inoculation method ranged from 36.58-38.93 m,7.80-8.98 mm, 14.75-17.23 cm, 7.15-8.23 cm, 0.35-0.50 cm respectively. The seed treatment growth attributes ranged from 37.52-39.93 m,7.75-9.0 mm, 15.50-18.23 cm, 7.23-8.98 cm, 0.40-0.52 cm. In contrast, un-inoculated plants has lower range 23.35 m, 5.78 mm, 10.42, 5.65 and 0.21 cm (seed treatment) and 25.13 m, 5.89 mm, 11.50 cm, 5.78 cm, 0.28 cm (soil inoculation). The interaction between the bacterial strains used and the inoculation methods of growth traits of C.annuum var. grossum was also examined which indicates that the inoculation methods influenced all the growth attribute of the plant.The result in the screen house experiment revealed that irrespective of the application method, inoculations with B. licheniformis, B. subtilis and Rhizobium significantly enhanced C. annuum var.grossum plants compared to the non-inoculated plants. Inoculations by seed treatment was generally more effective, produced taller plants than the soil inoculation. Therefore, this study has shown the potential benefits of co-inoculation of B. licheniformis, B. subtilis, and Rhizobium which could be utilized as effective bioinoculants to promote growth of C.annuum var. grossum under screen house conditions.