Institut für Phytomedizin

Permanent URI for this collectionhttps://hohpublica.uni-hohenheim.de/handle/123456789/14

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3D-surface MALDI mass spectrometry imaging for visualising plant defensive cardiac glycosides in Asclepias curassavica
(2021) Dreisbach, Domenic; Petschenka, Georg; Spengler, Bernhard; Bhandari, Dhaka R.
Mass spectrometry–based imaging (MSI) has emerged as a promising method for spatial metabolomics in plant science. Several ionisation techniques have shown great potential for the spatially resolved analysis of metabolites in plant tissue. However, limitations in technology and methodology limited the molecular information for irregular 3D surfaces with resolutions on the micrometre scale. Here, we used atmospheric-pressure 3D-surface matrix-assisted laser desorption/ionisation mass spectrometry imaging (3D-surface MALDI MSI) to investigate plant chemical defence at the topographic molecular level for the model system Asclepias curassavica. Upon mechanical damage (simulating herbivore attacks) of native A. curassavica leaves, the surface of the leaves varies up to 700 μm, and cardiac glycosides (cardenolides) and other defence metabolites were exclusively detected in damaged leaf tissue but not in different regions of the same leaf. Our results indicated an increased latex flow rate towards the point of damage leading to an accumulation of defence substances in the affected area. While the concentration of cardiac glycosides showed no differences between 10 and 300 min after wounding, cardiac glycosides decreased after 24 h. The employed autofocusing AP-SMALDI MSI system provides a significant technological advancement for the visualisation of individual molecule species on irregular 3D surfaces such as native plant leaves. Our study demonstrates the enormous potential of this method in the field of plant science including primary metabolism and molecular mechanisms of plant responses to abiotic and biotic stress and symbiotic relationships.
Efficacy of various mechanical weeding methods - single and in combination - in terms of different field conditions and weed densities
(2021) Naruhn, Georg-Peter; Peteinatos, Gerassimos G.; Butz, Andreas F.; Möller, Kurt; Gerhards, Roland
Public awareness and environmental policies have increased interest in applying non-herbicide weed control methods in conventional farming systems. Even though mechanical weed control has been used for centuries in agricultural practice, continuous developments—both in terms of implements and automation technologies—are continuously improving the potential outcomes. Current mechanical weed control methods were evaluated for their weed control efficacy and effects on yield potential against their equivalent herbicide methods. Furthermore, not much is known about the correlation between weed control efficacy (WCE) of different mechanical methods at varying weed density levels. A total of six experiments in winter wheat (2), peas (2), and soybean (2) were carried out in the years 2018, 2019, and 2020 in southwestern Germany. Harrowing and hoeing treatments at different speeds were carried out and compared to the herbicide treatments and untreated control plots. Regarding the average WCE, the combination of harrowing and hoeing was both the strongest (82%) and the most stable (74–100%) mechanical treatment in the different weed density levels. Whereas, in average, hoeing (72%) and harrowing (71%) were on the same WCE level, but harrowing (49–82%) was more stable than hoeing (40–99%). The grain yields in winter wheat varied between 4.1 Mg∙ha−1 (control) and 6.3 Mg∙ha−1 (harrow), in pea between 2.8 Mg∙ha−1 (hoe slow) and 5.7 Mg∙ha−1 (hoe fast) and in soybean between 1.7 Mg∙ha−1 (control) and 4 Mg∙ha−1 (herbicide). However, there were no significant differences in most cases. The results have shown that it is not possible to pinpoint a specific type of treatment as the most appropriate method for this cultivation, across all of the different circumstances. Different field and weather conditions can heavily affect and impact the expected outcome, giving, each time, an advantage for a specific type of treatment.
Enhancing weed suppression in plants by artificial stress induction
(2025) Merkle, Michael; Petschenka, Georg; Belz, Regina; Gerhards, Roland
Various plant species from the Poaceae, Cannabaceae, and Brassicaceae families are used as cover crops to suppress weeds and volunteer crops through competition and allelopathy. This study examined the effects of artificially induced stress on the physiological processes, total phenolic content (TPC), and allelopathic potential of the plant species Avena strigosa, Cannabis sativa , and Sinapis alba at an early growth stage with the aim to increase their weed suppression abilities. Stress was induced at the 3–4 leaf stage in greenhouse-grown plants via harrowing, methyl jasmonate (MeJA) application, insect stress simulation, or a combination of insect stress and harrowing. Maximum quantum yield of photosystem II and shoot dry matter in the three plant species were only minimally or not affected a few days after treatment (DAT). Insect stress caused visible symptoms on treated leaves in all plants. The TPC in the shoot extracts of combined stress-treated C. sativa and insect-stressed S. alba was significantly higher by 1.7 and 1.9 times, respectively, five DAT compared to the shoot extracts from untreated control plants. Additionally, laboratory bioassays with aqueous shoot extracts from the untreated and treated plants were conducted to identify changes in allelopathic potential within the shoot tissues. The application of shoot extracts from MeJA-treated C. sativa and S. alba resulted in the lowest seed germination rates for the two weed species Alopecurus myosuroides and Stellaria media , as well as for the volunteer wheat Triticum aestivum , which were up to 65% lower 10 DAT compared to seeds treated with shoot extracts from non-stressed plants. However, the root-suppressing effect of the shoot extracts on weeds was not influenced by the stress treatments. This study reveals that artificial stress induction can be a suitable management strategy to enhance weed and volunteer cereal suppression in plants in an early growth stage but may vary between stress types and plant species, and requires further optimization and field testing.
The potential of farnesene isomer mixtures to support the control of aphids in the cultivation of lettuce crops
(2025) Kuhn, Denise; Bauer, Philipp; Tolasch, Till; Petschenka, Georg; Steidle, Johannes L. M.; Kuhn, Denise; Department of Chemical Ecology 190 T, Institute of Biology, University of Hohenheim, 70599, Stuttgart, Germany; Bauer, Philipp; Department of Applied Entomology 360 C, Institute of Phytomedicine, University of Hohenheim, 70599, Stuttgart, Germany; Tolasch, Till; Department of Chemical Ecology 190 T, Institute of Biology, University of Hohenheim, 70599, Stuttgart, Germany; Petschenka, Georg; Department of Applied Entomology 360 C, Institute of Phytomedicine, University of Hohenheim, 70599, Stuttgart, Germany; Steidle, Johannes L. M.; Department of Chemical Ecology 190 T, Institute of Biology, University of Hohenheim, 70599, Stuttgart, Germany
(E)-ß-farnesene (EBF) acts as an alarm pheromone of many aphid species and is also used as an aphid repellent by plants. Upon perception of EBF, aphids exhibit avoidance behavior. They walk away, stop feeding or drop from leaves. Moreover, EBF is an attractant for natural enemies of aphids. However, EBF is not used in pest management because it is expensive in its pure form. Therefore, we assessed the effect of a less expensive farnesene isomer mixture (FIM) on Myzus persicae (Sternorrhyncha: Aphidiae) on lettuce ( Lactuca sativa var. Ulmo) in the laboratory and under field conditions. First, we tested under laboratory conditions if FIM has the same effect on M. persicae as it is described for pure EBF. The aphids were influenced by EBF. They stopped feeding, withdrew their stylets, went away from the danger zone, or developed and reproduced more slowly. Therefore, we studied the behavioral response of the aphids after FIM application and aphid reproduction under permanent exposure of FIM. Second, we tested in the field the reaction to FIM either directly applied to lettuce or released by dispensers. In the lab experiments, we found that M. persicae reacts to FIM by walking away and that reproduction tends to be reduced in the presence of FIM. In the field, we found lower numbers of aphids in the treatments with FIM. In particular, dispenser application caused higher aphid reduction compared to spray application on lettuce. In addition, more natural enemies of aphids could be found in dispenser-treated plots. Taken together, these results indicate that the use of FIM could contribute to insecticide-free aphid control in lettuce, but possibly also in other crops.

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