Yellow mealworm waste amendment in the control of Fusarium wlit and root-knot nematode in tomato

Abstract

Fungi that cause vascular wilt (Fusarium oxysporum) and the phytonematodes (Meloidogyne spp.) they are among the pathogens of importance to Brazil and global agriculture, impacting the productivity of most agricultural crops of economic or subsistence importance. The incorporation of organic waste amendments into the soil has several beneficial effects. They can act against pathogens through the release of toxic compounds produced during decomposition, and/or by stimulating of antagonistic soil microorganisms and inducing systemic resistance in plants. Thus, the present study aimed to evaluate the efficiency of yellow mealworm waste amendment (Tenebrio molitor) against Fusarium oxysporum f. sp. lycopersici race 3 (Fol 3) and Meloidogyne incognita race 1. The phytotoxicity of the waste was evaluated in the production of tomato seedlings and its effect on plant growth promoting. The effect of the aqueous extract was evaluated on mycelial growth and microconidia germination of Fol 3, and on the hatching, mobility and mortality of J2 of M. incognita. The effect of volatile compounds emitted by the waste on the mycelial growth of Fol 3, and on the hatching, mobility and mortality of J2 of M. incognita was evaluated. The suppressiveness of the waste was evaluated against Fol 3 and M. incognita in tomato plants. There was no toxicity to plants when the waste was incubated into the soil, and the weight was proportional to the waste concentrations. The lowest concentration of the aqueous extract reduced the germination of Fol 3 microconidia. The mycelial growth of the fungus was increased with extract concentrations. The J2 mobility of M. incognita was reduced with the lowest concentration of the extract. It also showed efficiency against J2 mortality and reduced its hatching. Regarding the volatile compounds emitted by the waste, the lower concentration reduced the Fol 3 mycelial growth. It also reduced mobility, had a nematicidal effect and affected the hatching of J2. All concentrations of the waste reduced the external severity of Fusarium wilt in tomato, represented by the AUDPC. There was an increase in photosynthesis, water use efficiency, and aerial and root system biomass. All waste concentrations reduced the J2 population in the soil. There was a reduction in the number of galls and eggs + J2 in the tomato root system. An increase in aerial and root system biomass was observed with concentrations of waste, with a reduction in physiological damage. Tomato productivity increased with waste concentrations. This is the first study relating yellow mealworm waste and its suppressive effect against pathogens, Fol 3 and M. incognita. The waste incubation into the soil provides a greater quantity of nutrients to plants, promoting their growth without causing phytotoxicity. The waste contains a microbiota, that can play several ecological roles for plant, and chitin, an important polymer in agriculture. Chitin oligomers and other toxic compounds, volatile or not, are involved in reducing mobility, increasing mortality and reducing J2 hatching of M. incognita, in addition to reducing mycelial growth and microconidia germination of Fol 3.