Effects of Single and Dual Applications of Selected Trichoderma and Bacillus Isolates on Performance of Dry Bean Seedlings Grown in Composted Pine Bark Growth Medium under Shadehouse Conditions

ABSTRACT

A shadehouse pot trial was conducted to study the efficiency of single and dual inoculations with selected Trichoderma and Bacillus isolates on performance of dry bean plants (Phaseolus vulgaris L.) grown in composted pine bark (CPB) potting medium. All the plant treatments inoculated with Trichoderma spp. and/or Bacillus spp. had higher photosynthetic efficiency (Fv/Fm values). Of the treatments, only B. subtilis B69 showed a significant increase (P = 0.02) in Fv/Fm values over the growth period. The Trichoderma and Bacillus treated plants showed increase in dry shoot biomass. The greatest degree of nodulation was observed in Trichoderma and/or Bacillus treated plants. Increase in nitrogen concentrations were observed in leaves of plants inoculated with Trichoderma and Bacillus isolates. Only T. atroviride SY3A significantly increased phosphorus concentrations in leaves. These results depict and highlight the role these organisms can play in plant root-plant growth promoting rhizobacteria or plant growth promoting fungi (PGPR/PGPF) interaction in a nutrient-poor growth medium.

Keywords:

• bacillus
• dry bean
• photosynthetic efficiency
• mineral uptake
• nodulation
• trichoderma

ACKNOWLEDGMENTS

The authors would like to thank the University of KwaZulu-Natal for funding this study and Dr. Isa Bertling for the PEA equipment used in this study.

Notes

^a Slope (Regression coefficient) describing the linear regression increase/decrease of Fv/Fm values for each treatment over the 4 week period in the shadehouse.

^b Significance level of increase/decrease of weekly measurements of Fv/Fm values for each treatment over a period of 4 weeks in the shadehouse.

∗,

∗∗Significant at P < 0.05 and P < 0.01, respectively.

^a Fv/Fm values from 0.8 indicates optimum efficiency of light usage; values between 0.7–0.8 indicates that plants are not stunted and efficiency of photosystem II is almost maximum; values between

∗,

∗∗Significantly different at P < 0.05 and P < 0.01 respectively.

∗∗∗Significantly different at P < 0.001.

∗∗∗Significantly different at P < 0.001;