Antagonismo de Trichoderma sp. ante el patógeno Stromatinia cepivora en el cultivo de cebolla

In Cost Rica, the onion crop is an important source of income for small and middle size farmers. The fungus Stromatinia cepivora, it has worldwide importance and specifically in Cartago (Granados, 2005, 2013; Metcalf et al., 2004). The control of S. cepivora is not easy, there are few resistant and commercial onion varieties and there are not many fungicides for this control. Due to these factors, biological control is a good option against white rot. Trichoderma is a soil fungal genus that includes species widely used as biological control agents in agriculture. The objective of the research was to evaluate the antagonism in vitro and in the field of Trichoderma isolated from producing areas in Cartago, Costa Rica, against S. cepivora. Isolation and characterization studies were conducted from onion bulbs with symptoms of the disease. Then antagonism essays were developed to show the effectiveness of selected strains. The strain identified as T. asperellum was antagonistic against S. cepivora, both in vitro and in the field test. This effectiveness was determined by the interaction between a specific antagonistic strain and a specific pathogenic strain. For the application of this control strategy, it is necessary to emphasize to farmers the importance of the actions to maintain the health and the preparation of the soil, which allow for the reduction in the inoculum levels, an essential factor for obtaining good crop yields. En Costa Rica, el cultivo de cebolla (Allium cepa) es una importante fuente de recursos para los pequeños y medianos agricultores. La pudrición blanca provocada por el hongo Stromatinia cepivora es una enfermedad importante del cultivo a nivel mundial y en Costa Rica específicamente en la provincia de Cartago (Granados, 2005, 2013; Metcalf et al., 2004). El manejo de S. cepivora no es fácil, ya que existen pocos cultivares comerciales resistentes y pocos fungicidas para combatirlo, estos factores hacen que el control biológico sea una opción contra la pudrición blanca. Trichoderma sp es un género de hongos que incluye especies utilizadas como agentes de control biológico. El objetivo de esta investigación consistió en evaluar el antagonismo de aislamientos de Trichoderma sp. provenientes de zonas productoras de cebolla de Cartago con respecto a S. cepivora. Se realizaron estudios de aislamiento y caracterización de S. cepivora y Trichoderma sp. a partir de bulbos con síntomas de la enfermedad. Posteriormente, se desarrollaron pruebas