Papaya seedlings colonized by the bio-agents Trichoderma harzianum and Pseudomonas fluorescens to control root-knot nematodes


  • M. S. Rao


Experiments were conducted to produce seedlings of papaya with roots colonized by Trichoderma harzianum and Pseudomonas fluorescens for the control of the root-knot nematode Meloidogyne incognita. Seed treatment with P. fluorescens (108 cfu/g) and application of P. fluorescens and T. harzianum (106 cfu/g), each at 5 g/kg soil, reduced significantly the eggs/egg-mass of Meloidogyne incognita. Nursery soil treated with formulations of either P. fluorescens or T. harzianum was not significantly effective in reducing the nematode root-galling index. However, root-knot nematode control was improved when both bio-agents were used in the nursery soil at a rate of 5 g/kg each. Combined use of P. fluorescens and T. harzianum did not affect root colonization by either bio-agent. Seed and soil treatment with the formulations of the bio-agents produced highly vigorous seedlings with significantly increased growth. The seedling roots were colonized by both the bio-agents, which, therefore, would be carried to the field on transplanted seedlings. Thus, the results outline the potential for the production of papaya seedlings with roots colonized by combined formulations of P. fluorescens and T. harzianum for the control M. incognita under field conditions.