Elicitation of defense responses in tomato against Meloidogyne javanica and Fusarium oxysporum f. sp. lycopersici wilt complex

In this study, Trichoderma harzianum BI was evaluated for its capability to reduce the incidence and severity of the root-knot nematode, Meloidogyne javanica, and Fusarium wilt, F. oxysporum f. sp. lycopersici, as causal agents of a complex disease of tomato in the laboratory and greenhouse conditions. Initial in vitro studies revealed that the parasitism of M. javanica eggs by T. harzianum BI was up to 49.6%. In dual culture tests, maximum growth inhibition of F. oxysporum f. sp. lycopersici by T. harzianum BI (55%) was observed on the fifth day in laboratory. In greenhouse studies, the efficiency of treatments was appraised by using nematode-related factors such as diameter of galls, number of galls per plant, number of egg masses per plant and also incidence of Fusarium wilt. The antagonistic fungus was further tested for its ability to induce production of defense related enzymes in tomato. The activity of phenylalanine ammonia lyase (PAL) was increased significantly in the seedlings treated with the antagonistic fungus in comparison with control and its maximum amount was reached on the fourth day after inoculation with T. harzianum BI. Thus, the present study shows that in addition to direct antagonism, induction of defense-related enzymes, by T. harzianum BI that are involved in PAL pathway contributed to enhanced resistance against invasion of M. javanica and F. oxysporum f. sp. lycopersici in tomato.