We present a series of newly identified chemical compounds that can induce resistance of plants and crops against various plant fungal (e.g. Botrytis cinerea) and oomycete diseases (e.g. downy mildew) as well as insect pests. These compounds act as elicitors of the plant’s induced resistance (IR), without killing the disease/pest-inducing organism. The series was obtained through an extensive screening for IR inducing
potential, of which one of the hits was selected (K14) and its structure further optimized, resulting in the current compound series. The mode of action of the best performing elicitor of the series was unravelled.
Despite the use of chemical pesticides, an estimated 17-30% of the 5 major commercial crops (wheat, maize, rice, potato and soybean) are still lost globally due to plant pests and diseases. Moreover, concerns on the negative impact of these cidal compounds on human health and the environment are raising, as well the number of pesticide-resistant pathogens/pests. To counteract these negative effects, the EU increased legislation stringency leading to the withdrawal of several successful pesticides from the market. The EU complementarily promotes low-pesticide-input disease management through programs such as Integrated Pest Management (IPM), which emphasizes the growth of a healthy crop with the least possible input of pesticides. The application of elicitors of the plant’s own resistance against diseases and pests perfectly fits into such IPM strategy.
So far commercial availability of such elicitors registered for crop protection is limited. Their discovery is challenging as it requires in planta studies in a tripartite interaction (plant-pathogen-elicitor) setup. To facilitate the discovery of new IR-elicitors, we developed an innovative high-throughput IR-marker-based screening platform. The latter was successfully applied to screen a library of 15,000 molecules, predesigned (i) for “agro-like” physiochemical properties, (ii) to exclude a priori generally toxic/cidal structures (as found in pesticides), and (iii) with low production cost.
One of the hits of this IR marker-based screening, was further validated in planta indicating broad spectrum IR against a variety of fungal/oomycete pathogens with wide-ranging lifestyles (necrotrophy and (hemi)biotrophy) in multiple plant species and through different application modalities (including on leaves, roots, or via hyodroponics).
Moreover, through an in-depth Structure-Activity Relationship (SAR) study, a series of analogues with improved IR-inducing activity were developed. For one of them induction of IR in the agricultural-relevant crop tomato against Botrytis cinerea, lasted for at least 2 weeks.