PTS and PTSO, two organosulfur compounds from onion by-products as a novel solution for plant disease and pest management

Background Over the past decade, the great impact of agricultural crop diseases has generated considerable economic losses and has compromised the production of edible crops at a time when the world population is only expected to rise, leading to the search for new pest management strategies. Besides that, the environmental impact resulting from the continued use of chemical pesticides has led to the search for natural and sustainable alternatives. One of the existing solutions that currently stands out for its effectiveness is the use of bioactive plant extracts. This study aims to evaluate the antimicrobial activity of propyl propane thiosulfinate (PTS) and propyl propane thiosulfonate (PTSO), two organosulfur compounds (OSCs) derived from Allium cepa , against a wide range of target bacteria and fungi. To this end, various in vitro procedures were conducted as well as soil sanitization tests using sterile substrate inoculated with soil-borne pathogens. In addition, this study also evaluates the pesticidal activity of both compounds through in vitro mortality and repellence tests. Results PTS and PTSO revealed inhibition activity on all the pathogens tested, belonging to different taxonomic groups. Moreover, both significatively reduced the population of bacteria and fungi in soil. The quantification of active substances in soil carried out in parallel to the microbial quantification showed that their use reduces the risk of residue accumulation since they break down quickly when applied. The set of antimicrobial tests performed demonstrated that the antifungal effect of both compounds is higher than the bactericidal effect. Lastly, PTS and PTSO showed a concentration-dependent significant biocidal and repellent effect against aphids. Conclusions The results presented in this work demonstrate that both PTS and PTSO have a significant antimicrobial and pesticidal activity against the great majority of phytopathogens tested, being a promising tool to improve pest management in crops. Graphical Abstract