Growth promotion and biological control of root-knot nematodes in micropropagated banana during the nursery stage by treatment with specific bacterial strains

The effect of strains EPS291 and EPS817 of Pseudomonas fluorescens to improve plant growth and nutrition as well as to reduce root-knot nematode in roots was investigated in micropropagated banana. Plantlets, cultured under commercial nursery conditions, were treated twice with bacteria after transplanting from in vitro conditions. Bacterial application was performed by drenching bacterial suspension containing approximately 10⁸ CFU (colony-forming units) g^-1 of substrate. Both strains significantly increased aerial fresh weight, plant length and leaf area, while the effect on other growth parameters depended on the strain. N content was also significantly increased after both bacteria treatments. A second experiment was performed to determine the potential biocontrol effect against the root-knot nematode Meloidogyne javanica. Following the same experimental conditions, Meloidogyne inoculum containing 10 500 nematodes was applied 15 days after the second bacteria treatment. At the end of the experiment, 135 days later, nematode reproduction in roots of bacterised bananas was significantly reduced. In both experiments, the inoculated bacteria colonised the root system and population levels in root, 5.5 months after transplanting were 6.8 × 10³ to 1.6 × 10⁴ CFU g^-1 fresh weight of root. The potential use of this technology to improve hardening stages in banana plant production in commercial nurseries is discussed.