اثر قارچ Trichoderma asperellum بر بیماری پژمردگی فوزاریومی خربزه در حضور و عدم حضور نماتد ریشه‏گرهی (Meloidogyne javanica)

Fusarium wilt disease of melon caused by the fungus Fusarium oxysporum f. sp. melonis, which is considered an important disease in melon. Since plant-parasitic nematodes facilitate the entrance of pathogenic fungi to the roots of plants, in this study, in order to investigate the effect of Trichoderma asperellum on fusarium wilt disease, root knot nematode (Meloidogyne javanica) was also considered as a treatment. This experiment was conducted in a completely randomized design in greenhouse conditions with eight treatments including field soil (control), soil inoculated with Trichoderma at a dose of 108/ml (control), soil infected with Fusarium at a dose of 109/ml (control), soil infected with root-knot nematode with a population of two eggs/g of soil (control), soil infected with root-knot nematode + Fusarium (control), soil infected with Fusarium + Trichoderma, soil infected with root-knot nematode + Trichoderma, soil infected with root-knot nematode + Fusarium + Trichoderma with three replications for each treatment. For this, seedling planting was done three days after fusarium and root-knot nematode inoculation and Trichoderma treatment was carried out three days after planting. Finally, after 18, 25, 35 and 50 days of soil contamination with both pathogens, melon plants were checked for wilt symptoms. Based on the results, the first mortality was observed in the treatment of the plant infected with root-knot nematode and Fusarium, which indicated the increase in mortality with the presence of the second pathogen (root-knot nematode). The mortality rate in this treatment intensified with the time and on day 35, all replications were completely eliminated. In the Fusarium infected control treatment, all replicates showed symptoms of yellowness and reduced growth after 25 days, and all the plants died after 50 days. From the observation at the end of the experiment, it is noted that the treatment of the plant infected with root-knot nematode + Fusarium + Trichoderma recorded a mortality rate of 100%, similar to that of the root-knot nematode + Fusarium, thus rendering the treatment using Trichoderma useless. The mortality rate in the treatment of plants infected with the Fusarium + Trichoderma-inhibiting fungus was 34% on the 25th day, stayed put on the 35th day, and reached 67% at the end of the experiment. For the plants receiving the root-knot nematode + Trichoderma infection, there was no difference compared with the treatment of plants infected by root-knot nematode concerning mortality. In general, the results showed that the presence of Trichoderma in the plants infected by Fusarium delayed the emergence of the symptoms caused by Fusarium.