Biological Control of Root-knot Nematode (Meloidogyne javanica) by Pseudomonas fluorescens CHA0 and Trichoderma harzianum BI in Tomato

Root-knot nematodes (Meloidogyne spp.) are among the most important groups of plant-parasitic nematodes, causing damage and yield losses to most cultivated plants. The bacterium Pseudomonas fluorescens CHA0 and the fungus Trichoderma harzianum BI were investigated for biological control capability and systemic induction of resistance against the nematode M. javanica under glasshouse conditions. Furthermore changes of peroxidase (POX) and polyphenol oxidase (PPO) activity in tomato were evaluated. In glasshouse tests, the results showed that tomato plants inoculated with both T. harzianum BI and P. fluorescens CHA0, nematode pathological indexes significantly decreased compared to P. fluorescens CHA0 inoculated as the sole biological agent and control (nematode), but there was no significant difference with T. harzianum BI inoculated plants. Results showed that the POX activity was started at the first day after nematode inoculation and reached to maximum level after the fourth day and then were decreased, There was no significantly different between T. harzianum BI and P. fluorescens CHA0 inoculated plant in comparison to P. fluorescens CHA0 inoculated plant alone. The polyphenol oxidase (PPO) activity reached to maximum level after five day in T. harzianum BI and P. fluorescens CHA0 inoculated plants. There was significant difference between treatments. So the both antagonists can induce plant defense mechanisms such as POX and PPO in tomato plant against nematode infection.