Abstract

Sensitivity to fungicides of wild and mutant strains of Trichoderma spp. for integrated control of tomato root and crown rot Rodrigo Herrera1 , Jaime Montealegre1 , David Nuñez1 , Natalia Romero1 , Ximena Besoaín2 , Luz M. Pérez3 1 Departamento de Sanidad Vegetal, Facultad de Ciencias Agronómicas, Universidad de Chile, Casilla 1004, Santiago, Chile, e-mail: [email protected]; 2 Pontificia Universidad Católica de Valparaíso, e-mail: [email protected]; 3 Universidad Andrés Bello, e-mail: [email protected] Abstract: In vitro sensibility of mycelia and conidia of Trichoderma strains to fungicides was studied. Trichoderma wild strains of several species (T. harzianum: Th 650, Th V, Th 291, Th 11, Th12; T. viride: Tvir 32; T. piluliferum: Tpi 33, and T. polisporum: Tpo 34) previously characterized and selected as good bioantagonists to control tomato root and crown rot (Fusarium oxysporum f. sp. lycopersici, F. solani, Pyrenochaeta lycopersici, Phytophthora nicotianae, and Rhizoctonia solani) were tested. Mutants were obtained with nitrosoguanidine and UV light, and their biocontrol activity was assessed on the pathogens mentioned above. The fungicides evaluated which are used normally or should be used to control tomato root and crown rot diseases, were Aliette, Enzone, Hymexazol, Mertec, Metalaxil, Monceren, Phyto-Fos, Rovcap and Rovral, The Trichoderma wild strains ThV, Tpi 33 and Th 11, had higher EAC50 at least for two fungicides, being less sensitive to the agrochemicals evaluated than the other wild strains. Fungicides Hymexazol and Phyto Fos caused little effect on the growth of the wild strains. None of the wild and mutant strains were affected by Monceren. On the other hand, fungicides Mertec and Rovral had the highest inhibitory effect. The mutant strains obtained from wild strains Th 11, Th 12 and Tvir showed higher EAC50 and MIC values, being less sensitive to the fungicides evaluated than their respective wild type.