Biological control of the root-knot nematode Meloidogyne javanica by Trichoderma harzianum

The filamentous fungi Trichoderma spp. is currently developed as biocontrol agents against many plant pathogens. Recent studies have shown that these fungi are able to infect nematode eggs and juveniles. In this research, biological control of root-knot nematode (Meloidogyne javanica) by Trichoderma harzianum BI was investigated in greenhouse and laboratory experiments. Results showed that different concentrations (102–108 spores/ml) of T. harzianum BI decreased nematode infection and other parameters significantly, compared to control. T. harzianum BI was able to penetrate nematode egg mass matrix and significantly decreased nematode egg hatching level. Specific activities of resistance-related enzymes, namely peroxidase (POX), polyphenol oxidase (PPO) and phenylalanine ammonia lyase (PAL) increased significantly in T. harzianum BI inoculated plants. Maximum activities of POX, PPO and PAL were observed at the 5, 5 and 6 days after inoculation, respectively. Chitinase activity was also increased in culture filtrates of T. harzianum BI grown on wheat bran moistened with salt solution supplemented with colloidal chitin or nematode eggs. Maximum activity of chitinase was recorded at the 4 days after inoculation, in media supplemented with colloidal chitin (1.15 U/min per ml) and nematode eggs (0.85 U/min per ml). Results suggested that direct parasitism of eggs through the increase in extracellular chitinase activity, which would be indicator of eggs infection capability, and inducing plant defense mechanisms leading to systemic resistance are two main suppression mechanisms used by T. harzianum BI against nematode.