The significance of volatile compounds of selected vegetables in the indirect defense of plants against slugs

Slugs and snails are economically important pests in agriculture. When attacked by harmful organisms, many plant species release volatile organic compounds (VOCs), which attract natural enemies of herbivores. VOCs act as chemical signals that directly influences both herbivores and their natural enemies. Mollusc feeding triggers quantitative and qualitative changes in certain metabolites in wounded leaves as well as in belowground roots. Among the many defence reactions, the synthesis of antioxidants and the activation of antioxidant enzymes that protect the plant from reactive oxygen species (ROS) are induced after attack. One of the most important antioxidants in plants is the tripeptide glutathione (GSH), and together with ascorbate, GSH is a key factor involved in the elimination of reactive oxygen species (ROS). GSH is involved in redox reactions and in the assimilative reduction of sulfur. It is further involved in the coordination of sulfate uptake and assimilation and in the plant's response to stress, as it activates defence genes and contributes to the development of sulfur-induced resistance (SIR). In herbivores, GSH further participates in the detoxification of harmful substances, including isothiocyanates, that are formed after the breakdown of glucosinolates by the enzyme myrosinase upon feeding with Brassicaceae. Biological control is a way of controlling harmful organisms in agriculture and forestry by using living natural enemies (beneficial organisms) or pesticides of biological origin. It is directed towards the protection, stimulation and targeted introduction of beneficial organisms outdoors or indoors. Biological preparations are ecologically more suitable, and their effects are more specific, so their formulation and application should be given particular attention, and optimal times of application should be strictly observed. The research aims to determine whether damage to aboveground parts of lettuce (Lactuca sativa) and cabbage (Brassica oleracea var. capitata) plants by different species of slugs (Spanish slug (Arion vulgaris) and grey field slug (Deroceras reticulatum)) induces the secretion of VOCs in the root system and to determine the role that these substances play in directing the movement of slug parasitic nematodes (SPN) (Phasmarhabditis hermaphrodita, Phasmarhabditis papillosa, Oscheius myriophila). We hypothesize that slug mucus, relative to wounding alone, induces the ascorbate-glutathione cycle. The aim of the proposed project is to determine whether increased glutathione levels in plants influence the chemotactic movement of slug nematodes and have a deterrent effect on slugs. For this purpose, we will promote sulfur-induced resistance (SIR) in plants by pretreatment of plants with sulfate. The objectives of the project are as follows: (1) our research aims to enrich the existing knowledge of multitrophic communication between organisms; (2) the main purpose of the research is primarily to determine which is the main communicator with SPN: plant or slug; (3) if the thesis that a plant or slug produces semiochemicals that are attractive to SPN is confirmed, it will be possible in the future to develop pheromone capsules based on the main active substance that would attract SPN to plant roots in greater numbers and this would provide better protection for plants; (4) this study also aims to optimize the methods of biological control of plants against harmful organisms and their implementation in food production; and (5) the study explores the development of optimized procedures for sampling and analysis of semiochemicals in selected organisms. Knowledge of communication among plants, herbivores and their natural enemies is crucial for more effective implementation and optimization of biological control in food production systems.