Antagonist Species to Streptomyces sp. that Causes Common Potato Scab

Potato scab is one of the main diseases affecting potato tubers during their development, causing great commercial damage to farmers. The use of some antagonistic microorganisms has been shown as a viable alternative to phytosanitary control of several crops. However, this work aimed to verify in vitro effects of microorganisms antagonistic against phytopathogenic Streptomyces sp. and in vivo treatment of scab in potato tubers. Trichoderma longibrachiatum; Trichoderma harzianum; Pochonia clamydosporia; Bacillus subtilis (except for in vivo test); Bacillus subtilis + Trichoderma longibrachiatum, and Bacillus subtilis + Enterococcus faecium were tested for in vitro growth inhibition of Streptomyces via microorganism radial pairing test, with both volatile and non-volatile metabolites. In parallel, the antagonistic microorganisms were tested in vivo in protected environments by cultivating potato plants in pots with soil contaminated with Streptomyces sp., then evaluating the number of injured tubers, injured area, severity index, production losses and the frequency of tubers by lesion type. The results indicate major in vitro inhibition of Streptomyces sp. by Trichoderma longibrachiatum, Trichoderma harzianum, and Bacillus subtilis + Enterococcus faecium under the antagonism (48 - 80%) and antibiosis tests, as well as a major reduction of tuber lesions size (34 - 60%), severity index, and production losses in the in vivo test.