InducTomE: optimizing plant performance under controlled stress conditions aiming towards increased accumulation of secondary metabolites in tomato leaves

InducTomE is an interdisciplinary, translational research project focusing on the potential of stress-induced accumulation of secondary metabolites (SM) in tomato for industrial utilization. Further aims are to establish the practical implementation of SM extraction and to evaluate the economic chain, from the supplier of raw material to industrial partners enabling the use of the compounds e.g., in the food or health care segments (www.biosc.de /inductome). The challenge in commercial-like greenhouses is the establishment and control of tolerable and well-reproducible stress levels that ensure highest yield and quality of fruit but at the same time also favour accumulation of SM in ‘waste-materials’, such as removed leaves, side-branches, stems and plant residues (at the end of the cultivation cycle). In this study we evaluated the impact of controlled water and nitrogen stress on plant performance and on the accumulation of selected secondary leaf components by non-invasive optical sensors, such as hyperspectral and fluorescence devices. Besides, SMs were quantitatively determined by high-pressure liquid chromatography (HPLC). PRI (photochemical reflectance index) and NDVI (normalized difference vegetation index) revealed an increased xanthophyll and decreased chlorophyll content in leaves indicating photoprotective processes. Fluorescence indices as well as rutin and solanesol content exhibited changes, apparently as consequence of changing environmental conditions, but not as direct response to the reduced water and nitrogen supply, as selected for our experiments. We conclude that slightly reduced nitrogen and water supply are promising treatments to increase contents of SM in leaves. However, intensity and timing of the treatments needs to be optimized in order to significantly increase SM accumulation without inducing fruit yield loss. The concept of the InducTomE project, e.g., SM induction, extraction and economic evaluation, will open up perspectives for other waste streams and metabolites and contribute to added value in horticultural production and to regional and national bio-economy.