Biological control of Setophoma terrestris isolated from onion rhizosphere in Costa Rica

Setophoma terrestris is a fungus that produces a disease named “pink root” in onion. It is a biotrophic organism that causes losses, decreasing the onion’s weight and diameter. It is difficult to have a pure culture because it is slow growth. In this study, it was improved a protocol to isolate the pathogen from infected roots, which were obtained from farms in Costa Rica. The principal isolate was characterised through microscopic and molecular tests and confirmed as S. terrestris. The Koch’s postulates also were confirmed. Additionally, it was evaluated the antagonism of Trichoderma virens, Trichoderma harzianum and Bacillus licheniformis in vitro dual culture assays. After 6 and 8 days, T. virens showed the greatest value of growth inhibition. For 12 days T. virens had the most important effect. The results are promissory for evaluation of these microorganisms as part of an integrated management program to reduce the use of agrochemicals in onion production.