TaReCa – Cascade utilization of horticultural biomass for a resource efficient production of valuable bioactive substances

Viele pflanzliche Sekundärmetabolite haben antioxidative oder andere bioaktive Eigenschaften, weshalb sie einerseits wichtige Bestandteile der menschlichen Ernährung sind, andererseits aber auch als pharmazeutische Verbindungen oder als Substrat für die chemische Synthese von bioaktiven Substanzen verwendet werden. Pflanzen induzieren die Produktion solcher nutzbaren Sekundärmetabolite wie z.B. Flavonoiden als Reaktion auf abiotischen Stress. Die Produktion von Gemüse und Früchten in Gewächshäusern hinterlässt große Mengen an ungenutzter pflanzlicher Biomasse, welche eine potentielle Ressource für die Gewinnung wertvoller Metabolite darstellt. Durch eine kaskadenartige Verwendung von Gartenbaukulturen zur Produktion von Früchten und Gemüse mit einer anschließenden Gewinnung hochwertiger Substanzen aus der verbleibenden Restbiomasse würde ein erheblicher Mehrwert generiert. Das Projekt TaReCa bearbeitet die Entwicklung einer maßgeschneiderten Kaskadenverwertung von Paprikapflanzen-Restbiomasse aus dem Gartenbau. Dabei soll der pflanzliche Sekundärmetabolismus durch spezifische abiotische Stressbedingungen nach der Fruchternte gezielt induziert werden, um die Konzentrationen der Zielmetaboliten zu steigern. Durch umweltfreundliche und wirtschaftliche Extraktionsprozesse und eine anschließende Verwertung des verbleibenden Pflanzenmaterials in einer Bioraffinerie wird die Wertschöpfungskette erweitert. Eine Analyse der Anwendungsgebiete sowie Untersuchungen zur Akzeptanz der induzierten Inhaltsstoffe, Prozesse und Technologien werden helfen, das Marktpotenzial der Restbiomasse für die Nutzung in Kaskaden zu evaluieren. Die maßgeschneiderte Nutzung von Gartenbaubiomasse durch Lebensmittelproduktion, Extraktion bioaktiver Sekundärmetabolite und Bioraffinerien kann wirtschaftlich relevante, biobasierte Produkte für industrielle Anwendungen erzeugen und somit zur Entwicklung einer nachhaltigen, effizienten und integrierten Bioökonomie beitragen, ohne mit der Lebensmittelproduktion zu konkurrieren.Many plant secondary metabolites have antioxidant or pharmaceutically relevant properties, which makes them important components of the human diet, but also as pharmaceutical compounds or for the chemical synthesis of bioactive substances. Plants induce the production of secondary metabolites, e.g. flavonoids in response to environmental stress stimuli. The production of vegetables and fruits in greenhouses leaves huge amounts of so far under-utilized biomass after fruit harvest, which is a potential source for production of valuable metabolites. A cascade utilization of horticultural crops to produce fruits and vegetables with subsequent extraction of high quality compounds would generate significant added value. The project TaReCa is working on the development of a tailored cascade utilization of bell pepper plant residues from horticulture. The secondary metabolism will be induced by specific abiotic stress treatments after the last fruit harvest, in order to increase the concentrations of the target metabolites. Eco-friendly and economical extraction processes and subsequent utilization of the remaining plant material in a biorefinery will expand the value chain. An analysis of the application areas as well as studies on the acceptance of the induced ingredients, processes and technologies will help to evaluate the market potential of the residual biomass for the proposed cascaded use. The tailored utilization of horticultural biomass in food production, extraction of bioactive secondary metabolites and biorefineries can produce economically relevant bio-based products for industrial applications and thus contribute to the development of a sustainable, efficient and integrated bioeconomy without competing with food production

Effects of Cercospora leaf spot disease on sugar beet genotypes with contrasting disease susceptibility

The fungal pathogen Cercospora beticola causes the most destructive foliar diseas eof sugar beet, namely Cercospora leaf spot (CLS), which results in economically important yield losses. Current breeding efforts aim at developing sugar beet lines with lower fungal susceptibility as well as high productivity to ensure reduced fungicide applications in the context of integrated pest management. However, the main challenge remains to select sugar beet genotypes that produce the required yield quality and quantity, and to quantify their defense ability. Well-established visual disease scoring can be supported and supplemented by new techniques that enable earlier disease detection and genotype resistance classification. In this thesis, visual disease scoring was combined with novel invasive and non-invasive techniques toanalyze shoot and root disease responses to Cercospora infection. The fungal growth within the sugar beet leaf tissue was quantified using molecular analysis of the fungal calmodulin gene. This allows for the pre-selection of resistant genotypes before disease symptoms were visible. It could be shown that plants with high susceptibility (HS) allowed a stronger fungal colonization in the leaf tissue than ones with low susceptibility (LS). These results correlated with the respective disease severity. The HS genotypes consistently displayed more severe disease symptoms than LS plants. In particular, the moderately susceptible (MS) genotype seemed to be a promising candidate according to its variable response indicating a more adaptable reaction to changing environmental conditions. Therefore, this MS genotype might produce more yield under low-to-moderate disease pressure compared with HS plants, which would be comparatively more strongly infected and deliver reduced yield. The cuticle forms a barrier between the plant and the environment and therefore provides resistance against pathogens. Cuticular wax may affect host-pathogen recognition and conidia adhesion on the leaf surface. In this study, LS plants werefound to contain larger amounts of cuticular waxes. Mature leaves, which showed reduced fungal colonization, also had higher wax levels than immature leaves. Further experiments are needed to investigate the precise role of sugar beet cuticular waxes on C. beticola infections.[...

HyperART: non-invasive quantification of leaf traits using hyperspectral absorption-reflectance-transmittance imaging

BackgroundCombined assessment of leaf reflectance and transmittance is currently limited to spot (point) measurements. This study introduces a tailor-made hyperspectral absorption-reflectance-transmittance imaging (HyperART) system, yielding a non-invasive determination of both reflectance and transmittance of the whole leaf. We addressed its applicability for analysing plant traits, i.e. assessing Cercospora beticola disease severity or leaf chlorophyll content. To test the accuracy of the obtained data, these were compared with reflectance and transmittance measurements of selected leaves acquired by the point spectroradiometer ASD FieldSpec, equipped with the FluoWat device.ResultsThe working principle of the HyperART system relies on the upward redirection of transmitted and reflected light (range of 400 to 2500 nm) of a plant sample towards two line scanners. By using both the reflectance and transmittance image, an image of leaf absorption can be calculated. The comparison with the dynamically high-resolution ASD FieldSpec data showed good correlation, underlying the accuracy of the HyperART system. Our experiments showed that variation in both leaf chlorophyll content of four different crop species, due to different fertilization regimes during growth, and fungal symptoms on sugar beet leaves could be accurately estimated and monitored. The use of leaf reflectance and transmittance, as well as their sum (by which the non-absorbed radiation is calculated) obtained by the HyperART system gave considerably improved results in classification of Cercospora leaf spot disease and determination of chlorophyll content.ConclusionsThe HyperART system offers the possibility for non-invasive and accurate mapping of leaf transmittance and absorption, significantly expanding the applicability of reflectance, based on mapping spectroscopy, in plant sciences. Therefore, the HyperART system may be readily employed for non-invasive determination of the spatio-temporal dynamics of various plant properties

Heat-Induced Cross-Tolerance to Salinity Due to Thermopriming in Tomatoes

Global plant production is challenged by unpredictable (a)biotic stresses that occur individually, simultaneously or staggered. Due to an increasing demand for environmentally friendly plant production, new sustainable, universal, and preventive measures in crop protection are needed. We postulate thermopriming as a suitable procedure that fulfills these requirements. Therefore, we performed thermopriming as a pre-conditioning on tomato transplants in combination with two subsequent salt stress treatments to evaluate their single and combined physiological effects on leaves and fruits with regard to plant performance, fruit yield and quality. We identified a cross-tolerance to salinity that was triggered by the preceding thermopriming treatment and resulted in an accumulation of phenols and flavonols in the leaves. Plant growth and fruit yield were initially delayed after the stress treatments but recovered later. In regard to fruit quality, we found an increase in carotenoid and starch contents in fruits due to thermopriming, while sugars and titratable acidity were not affected. Our results indicate that thermopriming can mitigate the impact of subsequent and recurrent stress events on plant performance and yield under production-like conditions

Novel S. pennellii × S. lycopersicum Hybrid Rootstocks for Tomato Production with Reduced Water and Nutrient Supply

Drought stress and nutrient deficiency are limiting factors in vegetable production that will have a decisive role due to the challenges of climate change in the future. The negative effects of these stressors on yield can be mitigated by crop grafting. The increasing demands for resource-use efficiency in crop production, therefore, require the development and phenotyping of more resilient rootstocks, and the selection of appropriate scions. We tested the effect of combined drought stress and nutrient deficiency on yield and fruit quality of the two tomato cultivars ‘Lyterno’ and ‘Tastery’ in the greenhouse, grafted onto different rootstock genotypes. The use of four different rootstocks, including two novel S. pennellii × S. lycopersicum hybrids and the proven-effective use of ‘Beaufort’, as well as self-grafted plants, allowed conclusions to be drawn about the differential stress mitigation of the rootstocks used. The stress-induced yield reduction of the scion ‘Lyterno’ can be mitigated more significantly by the novel hybrid rootstocks than by the commercial rootstock ‘Beaufort’. At the same time, however, the individual fruit weight and the lycopene content of the fruits were significantly reduced when grafted onto the hybrid rootstocks. In contrast, the cultivar ‘Tastery’ showed a weak stress response, so that a generally positive influence of the rootstocks independently of the scions could not be demonstrated. We conclude that, particularly for more sensitive cultivars, the selection of more resilient rootstocks offers the potential for sustainable and resource-efficient production not competing with the overall quality of tomatoes