IN VITRO AND IN VIVO INVESTIGATION OF PLANT GROWTH PROMOTING AND BIOPROTECTING RHIZOBACTERIA ON EARLY MAIZE PLANT GROWTH

Abstract

The use of soil microorganisms as biofertilizers and biocontrol agents in agriculture is important in maintaining the soil ecological balance and sustainability of agroecosystems. Rhizobacteria were isolated and identified from the rhizosphere of matured field grown with maize (Zea mays L.) at the field of Federal University of Agriculture, Abeokuta teaching and research farm. The effect of inoculation of maize seeds (Oba super 2) with rhizobacteria on growth promotion and bioprotection against Fusarium moniliforme were investigated in vitro and in pot experiment in a screen house. Eight treatments representative of at least all the different genera of the isolated rhizobacteria and an uninoculated control in both cases were used. Treatments were replicated 3 times in a completely randomised design. Data obtained were subjected to analysis of variance (ANOVA) and means separated using Fisher’s LSD test (P<0.05). Fifty four rhizobacteria were isolated and identified consisting of Bacillus cereus (22%), Pseudomonas aeruginosa (2%), Micrococcus acidophilus (26%), Proteus morganii (11%), Staphylococcus aureus (9%), Streptococcus faecium (28%) and Staphylococcus parasiticus (2%). The in-vitro growth promotion study revealed that there was no significance difference among treatments in plant height and root mass. However, Pseudomonas aeruginosa and Bacillus cereus significantly increased the plant height length (0.13-0.21) and root mass (0.10-0.12) above control. The in-vitro biocontrol screening revealed that none of the treatments except Pseudomonas aeruginosa and Bacillus cereus showed inhibition (2.0-2.5mm) against Fusarium moniliforme. Results from the screen house study showed that treatment significantly increased the plant height and root mass except Staphylococcus aureus and Staphylococcus parasiticus and only Bacillus cereus and Pseudomonas aeruginosa increased only the root mass. Bacillus cereus, Pseudomonas aeruginosa, Micrococcus acidophilus, Proteus morganii greatly reduce the recovery of the pathogen (Fusarium moniliforme) from infected seeds whereas Streptococcus faecalis was slightly effective. It was observed from the study that only Pseudomonas aeruginosa and Bacillus cereus had traits of plant growth and bioprotection and as such they have prospects for use as plant growth promoting and as biocontrol.