Institut für Phytomedizin

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

Browse

Now showing 1 - 20 of 115

Sensor‐based inter‐ and intra‐row weed control methods in sugar beet, sunflower, and maize
(2025) Gerhards, Roland; Spaeth, Michael; Alagbo, Oyebanji O.; Saile, Marcus; Gerhards, Roland; Weed Science Department, University of Hohenheim, Stuttgart, Germany; Spaeth, Michael; Weed Science Department, University of Hohenheim, Stuttgart, Germany; Alagbo, Oyebanji O.; Weed Science Department, University of Hohenheim, Stuttgart, Germany; Saile, Marcus; Weed Science Department, University of Hohenheim, Stuttgart, Germany
Sensor‐guidance and camera‐based weed detection systems have improved weed control, resulting in higher weed control efficacy (WCE), less herbicide use, and less crop damage. In this study, four sensor‐guided inter‐ and intra‐row weeding systems were tested in sugar beet, maize, and sunflower. Those four systems included (1) camera‐guided inter‐row hoeing (HOE), (2) HOE + intra‐row finger weeding (HOE+F), (3) HOE + camera‐guided intra‐row hoeing (HOE + InRow) and (4) HOE + intra‐row band spraying (HOE + BS). A broadcast herbicide treatment and an untreated plot were included as control. Six experiments were conducted in 2022 and 2023 in Southwestern Germany. Inter‐row and intra‐row weed density and crop density were assessed before and after treatment. Yield was measured for each plot. The systems were evaluated based on WCE, crop losses (CL), yield, and herbicide savings. All sensor‐based weeding systems controlled at least on average 77% of the weeds. HOE+BS achieved 91% WCE and was similar to the broadcast herbicide application (92% WCE). HOE on average controlled 90% of the inter‐row weeds but only 69% of the in‐row weeds. HOE and HOE+F had 14% less intra‐row WCE than inter‐row WCE. HOE+InRow resulted in 77% inter‐row and intra‐row WCE. Sensor‐guided weed control did not cause significant CL or yield reduction compared to the broadcast herbicide application, except for HOE+InRow in maize 2023 because of wrong setting in the segmentation and weed/crop classification algorithm. This study underlines that sensor‐guided hoeing and the combination of band spraying with inter‐row hoeing provide effective and robust alternatives to conventional broadcast herbicide application in row crops.
Herbicide reduction through Convolutional Neural Network (CNN)-based technologies for advanced weed control
(2024) Allmendinger, Alicia; Gerhards, Roland
Weeds are plants that can grow in agricultural fields and can compete with cultivated crops for essential resources, including light, water and nutrients. Such competition can result in yield losses, thereby necessitating the implementation of weed control measures by farmers. Traditional weed control is performed by the use of herbicides, which in previous years were applied in a uniform manner across the entire field. In recent years, there has been a growing awareness of the detrimental impact of herbicides on the environment, as well as on human health. Furthermore, the impact on the crop, biodiversity in agriculture and fauna was examined. Given that herbicides have been found in both groundwater and the food chain, there is an urgent need to develop alternative methods for site-specific weed control, rather than a uniform application. In addition to the complete avoidance of herbicides through mechanical weed control, such as in-row hoeing, methods including site-specific herbicide application and spot-spraying, represent a promising approach for consideration. In the context of a site-specific weed control the use of herbicides is confined to areas where weeds are actually present. Additionally, the use of a selective herbicide can be employed, which is targeted to specific weed species. Furthermore, the application of species is possible above a specific threshold. Site-specific weed control includes methods like spot-spraying, where only single weeds are treated, and also mechanical solutions such as in-row hoeing, which can also control weeds intra row. However, reliable detection and identification of the plants or plant species is essential to implement any of these methods effectively. The process of recognition in digital images is currently often facilitated by convolutional neural networks (CNNs). These systems are either used as online or offline systems. In online systems images are gathered with f.e. a camera mounted to the front of a tractor and plant species are identified directly on a tractor´s onboard computer by an image classifier. This process allows a real-time application of herbicides during a single pass. In offline systems, the field is scanned in advance by for example unmanned aerial vehicles (UAVs), which capture georeferenced images of the field. These images are analysed in the next step by an image classifier, which generates a weed control map, that is later uploaded to the tractor's terminal and an application of herbicides based on RTK-GNNS can be performed. This dissertation presents a summary of the current research in this field and offers an empirical test of an offline system in a practical agricultural setting. Moreover, multiple CNNs were trained using weed and crop images, and their efficacy for real-time detection was evaluated. The first article presents an overview of the current research in the domain of site-specific herbicide application. The article provides a summary of the existing technology and situates it within the context of current trends. Furthermore, a CNN-based modular spot sprayer is presented, which has been designed to facilitate communication between the tractor and the mounted implement via an ISOBUS connection. The second article addresses the utilisation of unmanned aerial vehicles (UAVs) for the generation of weed control maps in maize. Field trials were conducted on four fields at two locations in 2023 as part of the study. The efficacy of pre-emergence and post-emergence herbicides was evaluated and the post-emergence herbicide was applied in both broadcast and spot application. The timing of the post-emergence herbicide application was varied, with the first application occurring at the two-to-four-leaf stage and the second at the six-to-eight-leaf stage of the maize. The image classifier utilized for the weed control maps exhibited a detection accuracy of 94%. Weed control efficacy in spot spraying was 86%, comparable with the efficacy of the broadcast application. Using weed control maps resulted in a reduction of herbicide by up to 47% without any negative impact on the yield. This approach has the potential to reduce operational costs and the negative impact of herbicides on the environment. The third article presents the use of different CNNs for the differentiation between diverse plant species and the differentiation between crops, monocotyledonous weeds and dicotyledonous weeds. Therefore, all models of the networks YOLOv8, YOLOv9, YOLOv10 and RT-DETR that were available at that time were trained on different central processing units (CPUs) and graphic processing units (GPUs). The results demonstrated that a differentiation between individual weed species is feasible with a mean Average Precision (mAP) of up to 43.82 % at an Intersection over Union (IoU) threshold of 0.5 to 0.95. Nevertheless, greater accuracy can be attained by distinguishing only between crops, monocot and dicot weeds with mAP50-95 scores of up to 47.26 %. Moreover, it is evident that there are considerable fluctuations in inference time across the various models, with detection times ranging from 8.46 ms for YOLOv8n on the NVIDIA GeForce RTX 3090 GPU to 120.44 ms on the AMD Ryzen 9 5950X 16-Core CPU for species wise object detection. These findings underscore that GPU´s, with their faster processing times, are most suited for real-time application. The studies conducted show that precise distinguishing between plant species, and between weeds and crops, is achievable with precision scores exceeding 80 %. Nevertheless, for site-specific herbicide application or spot spraying this level of accuracy may be sufficient. In other applications, such as in-row hoeing, an accuracy of 80% may be insufficient, as this might cause great crop losses. Nevertheless, the implementation of CNN-based technologies, particularly the emerging RT-DETR, has the potential to significantly reduce the amount of herbicides used, thereby achieving the objectives of the EU Green Deal. Furthermore, these techniques allow for the implementation as online systems where suitable, as well as offline systems when more appropriate. However, for online systems it is essential to verify that the on-board computer of the tractor provides the necessary computational resources to support real-time applications. Additionally, for practical deployment on farms, the spraying technology must be available, with the compatible nozzles, that ensure for example accurate and effective spot spraying. Overall, spot-spraying can only be conducted with post-emergence herbicides; however, it would be beneficial reducing or even avoiding pre-emergence herbicides in order to achieve further savings, as these necessitate a broadcast application. When all of these optimisations are considered, it becomes evident that the objectives of the EU Green Deal are being met without compromising agricultural production yield.
Advancing cover cropping in integrated weed management through novel modelling approaches, management strategies, and allelopathic investigations
(2025) Merkle, Michael; Gerhards, Roland
Climate change, herbicide-resistant weeds, and the lack of new herbicidal modes of action are increasing the pressure on farmers to reduce herbicide usage. Environmentally friendly and integrated weed control methods, such as cover cropping – where cover crops (CCs) provide various ecosystem services, including the suppression of weeds and volunteer crops – can be implemented in crop rotations to minimize herbicide use. The intensity of this suppression var-ies between cover crop (CC) species. Additionally, it is influenced by the competitiveness, allelopathic activity, and biomass production of the CCs, as well as by the CC establishment method, sowing time, soil type, and climatic conditions. The prediction of weed suppression by CCs in the field, as well as the enhancement of their abilities to suppress weeds and volun-teer crops, is challenging. Furthermore, there are unstudied allelochemicals in CCs that could serve as herbicidal active ingredients in bioherbicide formulations. Therefore, this dissertation focused on the following research objectives: • Identifying models to predict weed suppression by winter-kill fall-to-spring CC spe-cies in the field; • Examining the impact of different establishment methods for winter-kill fall-to-spring CC species, including various sowing dates, to enhance their weed and volunteer cere-al suppressive abilities in the field; • Enhancing the allelopathic potential of winter-kill fall-to-spring CC species at an early growth stage by applying artificial stresses to improve their ability to suppress weeds and volunteer cereals; • Investigating phytocannabinoids derived from Cannabis sativa L. and aqueous C. sati-va shoot tissue extracts regarding their allelopathic effects on Zea mays L. and weeds, as well as their potential use as herbicidal active ingredients in bioherbicide formula-tions. The objectives of the dissertation were addressed in four research articles. The first research article compared two non-linear models to predict the weed suppressive ef-fect of six different winter-kill fall-to-spring CC species in the field. The models considered the shoot dry matter of the CCs and weeds (including volunteer crops) approximately 12 weeks after CC sowing, based on 11 field studies conducted between 2010 and 2020. Addi-tionally, the allelopathic potential of the CCs was considered in the models by investigating the allelopathic effects of aqueous shoot extracts from the shoot biomass of field-grown win-ter-kill fall-to-spring CCs on the seed germination of four different annual weed species in laboratory Petri dish bioassays. The three-parameter Weibull model was more accurate for predicting weed and volunteer crop suppression by CCs in the field than the Cousens model. Furthermore, the study showed that CCs with high allelopathic potential, such as Avena stri-gosa Schreb., can suppress weeds just as effectively (>80%) as Brassicaceae or Polygonaceae species, while requiring only one-third of the shoot biomass. The second research article compared three different establishment methods as well as differ-ent sowing dates for five different in monoculture sown winter-kill fall-to-spring CC species, along with a CC mixture, in a three-year field trial (2020–2022). The aim of this study was to improve the development, biomass production, and weed and volunteer suppression ability of CCs by identifying the most suitable establishment method and sowing date for each CC spe-cies and the CC mixture. The results showed that, 10 weeks after the harvest of the main crop, the establishment methods of pre-harvest sowing into the maturing cereal crop 10 days before harvest and direct sowing after cereal harvest without tillage resulted in, on average, 30% and 42% higher CC shoot dry matter and 81% and 78% lower weed density, respectively, com-pared to the post-harvest establishment method with reduced tillage. In contrast, the volunteer cereal densities and the weed and volunteer cereal control efficacies were consistent across the three CC establishment methods. However, the results varied among the different CC species and the trial years. The CC mixture demonstrated greater stability than monocultures regard-ing shoot biomass production under varying climatic conditions and establishment methods. In addition, the sowing date and climatic conditions had a significant impact on the success of CC establishment. The third research article investigated the effect of artificially induced stress on plant physio-logical processes and the allelopathic potential of CCs with the aim to enhance their suppres-sive effects on weeds and volunteer cereals during an early growth stage. Three different types of stress (mechanical stress through harrowing (1), phytohormonal stress by applying methyl jasmonate (2), and insect stress by applying Hermetia illucens paste with leaf injuries (3)) and a stress combination (1 + 3) were applied in greenhouse trials (2021–2022) to the CCs A. strigosa, C. sativa, and Sinapis alba L. at the 3-4 leaf stage. All applied stress types resulted in no or minimal changes in shoot biomass production and photosystem II activity of the CCs a few days after the stress application. The aqueous shoot tissue extracts from the shoot bio-mass of C. sativa subjected to combined stress and S. alba plants subjected to insect stress showed 1.7 and 1.9 times significantly higher total phenolic content, respectively, five days after stress application compared to the extracts of the control plants. Moreover, Petri dish bioassays were carried out under laboratory conditions using aqueous extracts derived from the shoot biomass of both treated and untreated CCs to assess stress-induced alterations in the allelopathic potential of their shoot tissues. The bioassays demonstrated that aqueous shoot tissue extracts from the shoot biomass of phytohormonally, insect- and combined-treated C. sativa and S. alba, as well as mechanically treated A. strigosa, exhibited stronger germination-inhibiting effects on the seeds of the two different annual weed species, as well as on volun-teer cereal seeds, compared to the seeds of the control plants that were treated with the aque-ous shoot tissue extracts from the shoot biomass of untreated CCs. In the fourth research article, five different phytocannabinoids derived from C. sativa and aqueous C. sativa shoot tissue extracts were investigated for their allelopathic effects on the cereal crop Z. mays and four different annual weed species in laboratory Petri dish bioassays and pre-emergence trials in the greenhouse (2021–2022). The application of phytocanna-binoids and aqueous shoot tissue extracts at the highest concentration significantly reduced root length in Z. mays and the four weed species by up to 91% in the bioassays, 10 days after treatment, compared to the untreated control plants. The application of phytocannabinoids in high concentrations in the bioassays primarily decreased the germination rate of the weed seeds by up to 53% compared to the untreated control plants. Depending on the weed species, the type of phytocannabinoid, and the concentrations applied, stimulatory effects on weed seed germination were also observed. In contrast, the germination of Z. mays seeds was not affected by the phytocannabinoids in the bioassays. However, high concentrations of the aqueous C. sativa shoot tissue extracts suppressed the germination rate of Z. mays seeds by 34% and that of the four weed species by 76–96%. In pre-emergence greenhouse experiments, stimulatory effects on the germination of Z. mays and four weed species were observed 21 days after the application of bioherbicidal formulations containing phytocannabinoids such as cannabidiol, cannabidivarin, or aqueous C. sativa shoot tissue extracts as active ingredients. In summary, this dissertation demonstrates that the suppression of weeds by winter-kill fall-to-spring CCs can be predicted using non-linear models and can be enhanced, along with the suppression of volunteer cereals, through suitable establishment methods, sowing dates, and CC species. The allelopathic potential of CCs, particularly that of their shoot tissues, can be increased through stress induction, and phytocannabinoids can have both stimulating and sup-pressive effects on Z. mays and weeds. These findings enhance the understanding of cover cropping in integrated weed management, particularly highlighting management strategies to improve the weed and volunteer cereal suppressive abilities of CCs.
Extracellular vesicles isolated from dsRNA-sprayed barley plants exhibit no growth inhibition or gene silencing in Fusarium graminearum
(2022) Schlemmer, Timo; Lischka, Richard; Wegner, Linus; Ehlers, Katrin; Biedenkopf, Dagmar; Koch, Aline; Schlemmer, Timo; Institute of Phytomedicine, University of Hohenheim, Stuttgart, Germany; Lischka, Richard; Centre for BioSystems, Land Use and Nutrition, Institute of Phytopathology, Justus Liebig University, Giessen, Germany; Wegner, Linus; Intitute of Botany, Justus Liebig University, Giessen, Germany; Ehlers, Katrin; Intitute of Botany, Justus Liebig University, Giessen, Germany; Biedenkopf, Dagmar; Centre for BioSystems, Land Use and Nutrition, Institute of Phytopathology, Justus Liebig University, Giessen, Germany; Koch, Aline; Institute of Phytomedicine, University of Hohenheim, Stuttgart, Germany
Numerous reports have shown that incorporating a double-stranded RNA (dsRNA)-expressing transgene into plants or applying dsRNA by spraying it onto their leaves successfully protects them against invading pathogens exploiting the mechanism of RNA interference (RNAi). How dsRNAs or siRNAs are transferred between donor host cells and recipient fungal cells is largely unknown. It is speculated that plant extracellular vesicles (EVs) function as RNA shuttles between plants and their pathogens. Recently, we found that EVs isolated from host-induced gene silencing (HIGS) or spray-induced gene silencing (SIGS) plants contained dsRNA-derived siRNAs. In this study, we evaluated whether isolated EVs from dsRNA-sprayed barley ( Hordeum vulgare ) plants affected the growth of the phytopathogenic ascomycete Fusarium graminearum . Encouraged by our previous finding that dropping barley-derived EVs on F. graminearum cultures caused fungal stress phenotypes, we conducted an in vitro growth experiment in microtiter plates where we co-cultivated F. graminearum with plant EVs isolated from dsRNA-sprayed barley leaves. We observed that co-cultivation of F. graminearum macroconidia with barley EVs did not affect fungal growth. Furthermore, plant EVs containing SIGS-derived siRNA appeared not to affect F. graminearum growth and showed no gene silencing activity on F. graminearum CYP51 genes. Based on our findings, we concluded that either the amount of SIGS-derived siRNA was insufficient to induce target gene silencing in F. graminearum, indicating that the role of EVs in SIGS is minor, or that F. graminearum uptake of plant EVs from liquid cultures was inefficient or impossible.
Legume-derived phenolic acids influence Fusarium oxysporum f.sp. strigae compatibility and biocontrol potential in a Striga push–pull system
(2025) Assena, Mekuria Wolde; Schöne, Jochen; Rasche, Frank
Biological control of Striga hermonthica (Del.) Benth. includes push–pull, intercropping using legumes, and soil-borne fungi such as Fusarium oxysporum f.sp. strigae (FOS). Efficacy of both technologies is compromised by various environmental factors. Combining them could potentially overcome their limitations and enhance control of S. hermonthica. It was hypothesized that FOS inoculation is compatible with push–pull intercropping, allowing consistent S. hermonthica suppression. Effects of selected phenolic acids and crude root exudates from three legume species (Mucuna pruriens, Desmodium uncinatum, Crotalaria juncea) on FOS mycelial growth and spore germination were studied. Bioassays showed that most phenolic acids (e.g., caffeic, p-hydroxybenzoic, syringic) had no effect on FOS development, except for piperonylic (80 %, 38 %) and t-cinnamic (53 %, 33 %) acids, which strongly inhibited growth at concentrations of 1 and 0.5 mM, respectively. Crude root exudates from Crotalaria inhibited FOS mycelial growth at 1 (44 %) and 0.5 (32 %) mg ml-1. Desmodium and Mucuna exudates showed no inhibition. Greenhouse results showed that legume intercropping and FOS inoculation reduced S. hermonthica emergence, with their integration achieving over 95 % suppression and boosting maize biomass. Legume presence enhanced FOS proliferation, with Mucuna and Desmodium increasing FOS gene copy numbers by over 44 %. LC-MS analysis identified nine phenolic acids, with p-coumaric (85–128 µg g−1) and p-hydroxybenzoic (50–97 µg g−1) acid being most abundant; the latter positively correlated with FOS abundance. In this setting, legume intercropping with maize did not impair FOS proliferation in rhizosphere soil and effectively suppressed S. hermonthica, demonstrating compatibility of FOS inoculation with push–pull for effective S. hermonthica management.
Mating-type analysis in Diaporthe isolates from soybean in central Europe
(2025) Hosseini, Behnoush; Käfer, Lena Sophia; Link, Tobias Immanuel; Cai, Lei
Species of the genus Diaporthe have a mating-type system with the two mating types MAT1-1 and MAT1-2, like other ascomycetes. They can either be heterothallic, which means that any isolate only possesses one of the two mating types and needs a mating partner for sexual reproduction, or homothallic, which means that they possess both mating types and are self-fertile. For several Diaporthe species, no sexual reproduction has been observed so far. Using PCR with primers specific to the defining genes MAT1-1-1 and MAT1-2-1 , we determined the mating types of 33 isolates of Diaporthe caulivora , D. eres , D. longicolla , and D. novem from central Europe. In addition, we partially sequenced the mating-type genes of 25 isolates. We found that different D. longicolla isolates either possess MAT1-1-1 or MAT1-2-1, making the species heterothallic, which is in contrast to previous studies and the general assumption that D. longicolla only reproduces asexually. D. eres and D. novem were also found to be heterothallic. Using genomic sequence information and re-sequencing of DNA and RNA, we identified the MAT1-1-1 gene in D. caulivora and present here the full sequence of the mating-type locus of this homothallic species. Finally, we used sequence information from MAT1-1-1 and MAT1-2-1 , respectively, for improved phylogenetic resolution of our isolates.
Arthropods as possible vectors of grapevine trunk disease pathogens in German vineyards
(2025) Brandenburg, Elisa; Vögele, Ralf
The health of grapevines worldwide is highly threatened by grapevine trunk diseases (GTDs), which are caused by various fungal pathogens that colonize and destroy the vascular system of the vine wood. The esca disease complex is one of the most important GTDs. Typical symptoms are the characteristic "tiger stripe" patterns on leaves, gummosis, necrosis and white rot inside the vine wood as well as the sudden dying of individual shoots or even the entire vine. The ascomycetes Phaeomoniella chlamydospora and members of the genera Phaeoacremonium and Cadophora can cause the death of even young vines. Air currents and/or rain splashes carry the pathogenic spores to their entry points in the vine wood, which are mainly susceptible winter pruning wounds. The involvement of arthropods has also been described in South African studies. The aim of this dissertation was to determine and evaluate the risk of arthropod-mediated transmission of GTD pathogens for German vineyards. Over the course of two years (2019-2020), the spectrum of possible vectors was determined in two different vineyards and arthropod visits of presumably susceptible winter pruning wounds were documented using camera-based monitoring in April 2019. The presence of esca-related pathogens on the exoskeletons of various arthropods was examined using nested multiplex PCR. Of the total of 2099 samples, 35 %, 21 % and 7 % tested positive for Pa. chlamydospora, Phaeoacremonium spp. and C. luteo-olivacea, respectively. The European earwig (Forficula auricularia) and various spiders were the most common arthropods on vines, with frequencies of 30 % and 27 %, respectively. Under artificial conditions, it was confirmed that earwigs and black garden ants (Lasius niger) can transmit the pathogens Pa. chlamydospora and Pm. minimum to healthy potted vines. The potential of earwig feces as an inoculum source for Pa. chlamydospora and Pm. minimum was also discussed. Under artificial conditions, it was shown that the germination ability of the spores is not impaired by earwig gut passage and that healthy potted vines can be infected with contaminated earwig feces. However, fecal samples from earwigs collected in vineyards showed only a very low detection rate of at least esca pathogens. The number of Pa. chlamydospora spores on the exoskeletons of earwigs, ants and two jumping spider species collected in vineyards was determined by qPCR. The spore number was in 40 % of the samples that had previously tested positive for Pa. chlamydospora in the nested PCR below the detection limit of the qPCR. In 56 % of the samples analyzed by qPCR, fewer than 1000 spores were detected. Under natural conditions, a number of 100-2000 Pa. chlamydospora-spores is sufficient to infect susceptible wounds in the vine wood. In this work, the mycobiome of the surface of the exoskeleton of earwigs collected in vineyards was analyzed for the first time. Nine GTD-associated genera were detected, of which Phaeomoniella and Eutypa were found to have relative abundances of 6.6 % and 2.8 %, respectively. This could indicate a possible involvement of earwigs in the dissemination of esca and eutypiosis. The present investigations have shown that arthropod-mediated transmission of GTDs, especially esca pathogens, is theoretically possible in vineyards. However, the practical relevance of this fact seems low compared to the numbers of airborne spores of the pathogens, especially Pa. chlamydospora, detected during the presumed period of susceptibility of winter pruning wounds. In addition, the simultaneous occurrence of susceptible winter pruning wounds and potential vectors in the field is only present with late-pruned vines, while the risk of wounds during the growing season requires a more detailed assessment. The results of this work underline the importance of protecting all types of wounds in the vine wood in order to reduce the invasion of pathogens.
Kinetics and dynamics of plant toxins in sequestering insects
(2024) Betz, Anja; Petschenka, Georg
Many plants produce a variety of chemical compounds to protect themselves from herbivorous insects. However, numerous insects have developed adaptations to tolerate and even utilize these toxins. These adaptations can include behavioral changes (feeding on or avoiding toxic plant parts), detoxification (metabolizing or excreting the toxins), barriers (preventing uptake or protecting target sites), or sequestration (storing secondary plant compounds in the body for self-defense). A widely distributed group of phytochemicals are the cardiac glycosides, which have been extensively studied in chemical ecology. These toxic steroids act in a highly specific manner by inhibiting the Na+/K+-ATPase, an essential transmembrane cation carrier that is ubiquitously expressed in animal cells. A cardiac glycoside-resistant Na+/K+-ATPase was first described in the monarch butterfly (Danaus plexippus, Lepidoptera: Danaini), which sequesters cardiac glycosides from its food plants. This led to the hypothesis that the evolution of a resistant Na+/K+-ATPase is linked to the sequestration of cardiac glycosides. It is now known that species from at least six insect orders possess Na+/K+-ATPases with reduced affinity for cardiac glycosides. This resistance is mediated by a few amino acid substitutions in the binding site, a mechanism referred to as "target site insensitivity." Interestingly, the ability to tolerate dietary cardiac glycosides does not necessarily require a resistant Na+/K+-ATPase. For example, the non-sequestering common crow (Euploea core, Lepidoptera: Danaini) can develop on cardiac glycoside-containing plants without expressing a resistant Na+/K+-ATPase. Although plant toxin sequestration has been documented in more than 275 insect species, the underlying kinetics and dynamics of toxin transport - such as the duration and mode of transport, target sites, barriers, and potential modified binding sites - remain largely unknown. Like the Danaini, milkweed bugs (Heteroptera: Lygaeinae) also have the ability to sequester cardiac glycosides. Remarkably, one species within this family, Spilostethus saxatilis, is able to sequester not only cardiac glycosides but also colchicine alkaloids from autumn crocus (Colchicum autumnale, Liliales: Colchicaceae). Colchicine binds to unpolymerized betatubulin at the interface with alpha-tubulin, thereby inhibiting microtubule formation. However, it is not known how colchicine resistance is achieved in S. saxatilis and whether there is also target site insensitivity. In my dissertation, I investigated the mechanisms behind the sequestration of cardiac glycosides in D. plexippus and colchicine in S. saxatilis within a phylogenetic framework. In D. plexippus, I was able to show that sequestration begins at the behavioral level, because unlike related species, caterpillars can increase their toxicity in the adult stage by drinking plant latex containing cardiac glycosides. I also found that a large portion of cardiac glycosides is lost during metamorphosis, suggesting that excessive toxin intake during the larval stage may be important. Furthermore, I could show that the uptake of the toxin by the intestinal epithelium is a very rapid process although probably not specific to D. plexippus, as uptake in nonsequestering lepidopterans does also occur. Regarding the sequestration of colchicine in S. saxatilis, I identified an amino acid substitution in the colchicine binding site of tubulin. Subsequently, an in vitro colchicine binding assays with crude tubulin extract of bug tissue and an in vivo feeding experiment with genetically modified Drosophila with one matching substitution in the colchicine binding site were conducted. Together both experiments suggest that this modification may play a crucial role in the sequestration of colchicine, indicating a novel natural target site resistance. My dissertation provides new insights into how insects adapt to toxic food plants and how they sequester their toxic metabolites. This contributes not only to a better understanding of how insects cope with natural plant toxins, but also to a better understanding of the physiological complexity of these adaptations.
Hohenheimer Lexikon der Agrarbiografien
„Persönlichkeiten aus Land- und Forstwirtschaft, Gartenbau und Veterinärmedizin“
(2025) Boettcher, Hartmut; Raupp, Manfred G.
Development and testing of a precision hoeing system for re-compacted ridge tillage in maize
(2024) Alagbo, Oyebanji O.; Saile, Marcus; Spaeth, Michael; Schumacher, Matthias; Gerhards, Roland
Ridge tillage (RT) is a conservation practice that provides several benefits such as enhanced root growth and reduced soil erosion. The objectives of this study were to develop an autosteered living mulch seeder and hoeing prototype for RT systems using RTK-GNSS (real-time kinematic global navigation satellite systems) created ridges as a guide. It was also aimed to compare weed control efficacy and crop response of ridge-hoeing compared to conventional hoeing in flat tillage (FT). It was further aimed to investigate the impact of a new RT technology (with ridge re-compaction) on maize root development, yield, soil temperature, and moisture compared to FT. Field experiments were conducted with maize in 2021 and 2022 in a two-factorial split-plot design with tillage (RT and FT) as main treatment and weed control (untreated, herbicide, twice hoeing, hoeing + living mulch) as sub-treatment factors. Weed density, coverage, biomass, crop density, weed control efficacy (WCE) and maize silage yield were assessed. Temperature loggers were installed within RT and FT to take temperature readings at 20 min. Soil moisture and root penetrability were measured every two weeks in each plot using soil samples and a penetrometer. The WCE and yield did not differ significantly between the tillage systems. Twice hoeing resulted in 71–80 % WCE, which was equal to herbicide treatment. Hoeing + living mulch achieved 70–72 % WCE. Different from previous studies with ridge tillage, temperatures in the compacted ridges did not consistently differ from the ridge valleys and flat seedbeds. Root penetration (against 1.4 MPa penetrometer cone index) was 40 % higher in RT than in FT. On average, RT maize produced more (53.6 g m−2) root biomass compared to FT. In summary, re-compacted ridges built along RTK-GNSS lines can allow post-emergent hoeing and living mulch seeding along ridges and also provide good growing conditions for maize.
A novel dataset of annotated oyster mushroom images with environmental context for machine learning applications
(2024) Duman, Sonay; Elewi, Abdullah; Hajhamed, Abdulsalam; Khankan, Rasheed; Souag, Amina; Ahmed, Asma
State-of-the-art technologies such as computer vision and machine learning, are revolutionizing the smart mushroom industry by addressing diverse challenges in yield prediction, growth analysis, mushroom classification, disease and deformation detection, and digital twinning. However, mushrooms have long presented a challenge to automated systems due to their varied sizes, shapes, and surface characteristics, limiting the effectiveness of technologies aimed at mushroom classification and growth analysis. Clean and well-labelled datasets are therefore a cornerstone for developing efficient machine-learning models. Bridging this gap in oyster mushroom cultivation, we present a novel dataset comprising 555 high-quality camera raw images, from which approximately 16.000 manually annotated images were extracted. These images capture mushrooms in various shapes, maturity stages, and conditions, photographed in a greenhouse using two cameras for comprehensive coverage. Alongside the images, we recorded key environmental parameters within the mushroom greenhouse, such as temperature, relative humidity, moisture, and air quality, for a holistic analysis. This dataset is unique in providing both visual and environmental time-point data, organized into four storage folders: “Raw Images”; “Mushroom Labelled Images and Annotation Files”; “Maturity Labelled Images and Annotation Files”; and “Sensor Data”, which includes time-stamped sensor readings in Excel files. This dataset can enable researchers to develop high-quality prediction and classification machine learning models for the intelligent cultivation of oyster mushrooms. Beyond mushroom cultivation, this dataset also has the potential to be utilized in the fields of computer vision, artificial intelligence, robotics, precision agriculture, and fungal studies in general.
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.
Role of benzoic acid and lettucenin A in the defense response of lettuce against soil-borne pathogens
(2021) Windisch, Saskia; Walter, Anja; Moradtalab, Narges; Walker, Frank; Höglinger, Birgit; El-Hasan, Abbas; Ludewig, Uwe; Neumann, Günter; Grosch, Rita
Soil-borne pathogens can severely limit plant productivity. Induced defense responses are plant strategies to counteract pathogen-related damage and yield loss. In this study, we hypothesized that benzoic acid and lettucenin A are involved as defense compounds against Rhizoctonia solani and Olpidium virulentus in lettuce. To address this hypothesis, we conducted growth chamber experiments using hydroponics, peat culture substrate and soil culture in pots and minirhizotrons. Benzoic acid was identified as root exudate released from lettuce plants upon pathogen infection, with pre-accumulation of benzoic acid esters in the root tissue. The amounts were sufficient to inhibit hyphal growth of R. solani in vitro (30%), to mitigate growth retardation (51%) and damage of fine roots (130%) in lettuce plants caused by R. solani, but were not able to overcome plant growth suppression induced by Olpidium infection. Additionally, lettucenin A was identified as major phytoalexin, with local accumulation in affected plant tissues upon infection with pathogens or chemical elicitation (CuSO4) and detected in trace amounts in root exudates. The results suggest a two-stage defense mechanism with pathogen-induced benzoic acid exudation initially located in the rhizosphere followed by accumulation of lettucenin A locally restricted to affected root and leaf tissues.
Assessment of a postharvest treatment with pyrimethanil via thermo-nebulization in controlling storage rots of apples
(2021) Büchele, Felix; Neuwald, Daniel A.; Scheer, Christian; Wood, Rachael M.; Vögele, Ralf T.; Wünsche, Jens N.
Apples are very susceptible to infections from various fungal pathogens during the growing season due to prolonged exposure to environmental influences in the field. Therefore, a strict and targeted fungicide strategy is essential to protect fruit and trees. Increased environmental and health concerns and pathogen resistance have resulted in a rising demand to reduce fungicide usage and residues on marketed fruit. Thus, producers must develop new plant protection strategies to conform to the legal and social demands while still offering high-quality apples. This study assessed the efficacy of a post-harvest fungicide treatment with pyrimethanil via thermo-nebulization for controlling storage rots and compared the results to those of standard pre-harvest fungicide strategies. The results showed that a single post-harvest application of pyrimethanil successfully controlled storage rots and is comparable to strategies using multiple pre-harvest fungicide applications. The control of fungal rot was sustained even after 5 months of storage and 2 weeks of shelf life. Thermo-nebulization into the storage facility allowed for a lower dosage of fungicide to be used compared to pre-harvest applications, while still maintaining optimal rot control. Residue analyses showed that the post-harvest fungicide treatment did not exceed legal or retailer’s standards.
Exploring the effects of different stubble tillage practices and glyphosate application combined with the new soil residual herbicide cinmethylin against Alopecurus myosuroides Huds. in winter wheat
(2022) Messelhäuser, Miriam Hannah; Saile, Marcus; Sievernich, Bernd; Gerhards, Roland
Effective control of Alopecurus myosuroides Huds. (blackgrass) solely with a chemical treatment is not guaranteed anymore because populations exhibit resistance to almost all herbicide modes of action. Integrated weed management (IWM) against blackgrass is necessary to maintain high weed control efficacies in winter cereals. Four field experiments were conducted in Southwest Germany from 2018 to 2020 to control A. myosuroides with a combination of cultural and chemical methods. Stubble treatments, including flat, deep and inversion soil tillage; false seedbed preparation and glyphosate use, were combined with the application of the new pre-emergence herbicide cinmethylin in two rates in winter wheat. Average densities of A. myosuroides in the untreated control plots were up to 505 plants m−2. The combination of different stubble management strategies and the pre-emergence herbicide cinmethylin controlled 86–97% of A. myosuroides plants at the low rate and 95–100% at the high rate until 120 days after sowing. The different stubble tillage practices varied in their efficacy between trials and years. Most effective and consistent were pre-sowing glyphosate application on the stubble and stale seedbed preparation with a disc harrow. Stubble treatments increased winter wheat density in the first year but had no effect on crop density in the second year. Pre-emergence application of cinmethylin did not reduce winter wheat densities. Multiple tactics of weed control, including stubble treatments and pre-emergence application of cinmethylin, provided higher and more consistent control of A. myosuroides. Integration of cultural weed management could prevent the herbicide resistance development.
Agronomic and technical evaluation of herbicide spot spraying in maize based on high-resolution aerial weed maps - an on-farm trial
(2024) Allmendinger, Alicia; Spaeth, Michael; Saile, Marcus; Peteinatos, Gerassimos G.; Gerhards, Roland; Allmendinger, Alicia; Department of Weed Science, Institute for Phytomedicine, University of Hohenheim, 70599 Stuttgart, Germany; (A.A.);; Spaeth, Michael; Department of Weed Science, Institute for Phytomedicine, University of Hohenheim, 70599 Stuttgart, Germany; (A.A.);; Saile, Marcus; Department of Weed Science, Institute for Phytomedicine, University of Hohenheim, 70599 Stuttgart, Germany; (A.A.);; Peteinatos, Gerassimos G.; ELGO-DIMITRA, Leof Dimokratias 61, Agii Anargiri, 135 61 Athens, Greece;; Gerhards, Roland; Department of Weed Science, Institute for Phytomedicine, University of Hohenheim, 70599 Stuttgart, Germany; (A.A.);; Rossi, Vittorio
Spot spraying can significantly reduce herbicide use while maintaining equal weed control efficacy as a broadcast application of herbicides. Several online spot-spraying systems have been developed, with sensors mounted on the sprayer or by recording the RTK-GNSS position of each crop seed. In this study, spot spraying was realized offline based on georeferenced unmanned aerial vehicle (UAV) images with high spatial resolution. Studies were conducted in four maize fields in Southwestern Germany in 2023. A randomized complete block design was used with seven treatments containing broadcast and spot applications of pre-emergence and post-emergence herbicides. Post-emergence herbicides were applied at 2–4-leaf and at 6–8-leaf stages of maize. Weed and crop density, weed control efficacy (WCE), crop losses, accuracy of weed classification in UAV images, herbicide savings and maize yield were measured and analyzed. On average, 94% of all weed plants were correctly identified in the UAV images with the automatic classifier. Spot-spraying achieved up to 86% WCE, which was equal to the broadcast herbicide treatment. Early spot spraying saved 47% of herbicides compared to the broadcast herbicide application. Maize yields in the spot-spraying plots were equal to the broadcast herbicide application plots. This study demonstrates that spot-spraying based on UAV weed maps is feasible and provides a significant reduction in herbicide use.
CRISPR/SpCas9‐mediated double knockout of barley Microrchidia MORC1 and MORC6a reveals their strong involvement in plant immunity, transcriptional gene silencing and plant growth
(2021) Galli, Matteo; Martiny, Engie; Imani, Jafargholi; Kumar, Neelendra; Koch, Aline; Steinbrenner, Jens; Kogel, Karl‐Heinz
The Microrchidia (MORC) family proteins are important nuclear regulators in both animals and plants with critical roles in epigenetic gene silencing and genome stabilization. In the crop plant barley (Hordeum vulgare), seven MORC gene family members have been described. While barley HvMORC1 has been functionally characterized, very little information is available about other HvMORC paralogs. In this study, we elucidate the role of HvMORC6a and its potential interactors in regulating plant immunity via analysis of CRISPR/SpCas9‐mediated single and double knockout (dKO) mutants, hvmorc1 (previously generated and characterized by our group), hvmorc6a, and hvmorc1/6a. For generation of hvmorc1/6a, we utilized two different strategies: (i) successive Agrobacterium‐mediated transformation of homozygous single mutants, hvmorc1 and hvmorc6a, with the respective second construct, and (ii) simultaneous transformation with both hvmorc1 and hvmorc6a CRISPR/SpCas9 constructs. Total mutation efficiency in transformed homozygous single mutants ranged from 80 to 90%, while upon simultaneous transformation, SpCas9‐induced mutation in both HvMORC1 and HvMORC6a genes was observed in 58% of T0 plants. Subsequent infection assays showed that HvMORC6a covers a key role in resistance to biotrophic (Blumeria graminis) and necrotrophic (Fusarium graminearum) plant pathogenic fungi, where the dKO hvmorc1/6a showed the strongest resistant phenotype. Consistent with this, the dKO showed highest levels of basal PR gene expression and derepression of TEs. Finally, we demonstrate that HvMORC1 and HvMORC6a form distinct nucleocytoplasmic homo‐/heteromers with other HvMORCs and interact with components of the RNA‐directed DNA methylation (RdDM) pathway, further substantiating that MORC proteins are involved in the regulation of TEs in barley.
Successful silencing of the mycotoxin synthesis gene TRI5 in fusarium culmorum and observation of reduced virulence in VIGS and SIGS experiments
(2022) Tretiakova, Polina; Voegele, Ralf Thomas; Soloviev, Alexander; Link, Tobias Immanuel
Crops constantly experience various biotic stresses during their life cycle, and Fusarium spp. remain one of the most serious groups of pathogens affecting plants. The ability to manipulate the expression of certain microorganism genes via RNAi creates the opportunity for new-generation dsRNA-based preparations to control a large number of diseases. In this study, we applied virus-induced gene silencing (VIGS), and spray-induced gene silencing (SIGS) to silence the trichothecene-producing gene TRI5 in F. culmorum as a means to reduce its aggressiveness on spring wheat. Treatment of the fungus with dsTRI5RNA in vitro reduced deoxynivalenol (DON) and 3-acetyldeoxynivalenol (3-A-DON) accumulations by 53–85% and 61–87%, respectively, and reduced TRI5 expression by 84–97%. VIGS decreased the proportion of infected wheat spikelets by 73%, but upregulation was observed for TRI5. SIGS on wheat leaves and ears using certain dsTRI5RNA amounts negatively impacted F. culmorum growth. However, when performing in vivo analyses of TRI5 mRNA levels, the upregulation of the gene was determined in the variants where fungal colonization was restricted, suggesting a compensatory reaction of the pathogen to RNAi.
Advances in site-specific weed management in agriculture: A review
(2022) Gerhards, Roland; Andújar Sanchez, Dionisio; Hamouz, Pavel; Peteinatos, Gerassimos G.; Christensen, Svend; Fernandez‐Quintanilla, Cesar
The developments of information and automation technologies have opened a new era for weed management to fit physical and chemical control treatments to the spatial and temporal heterogeneity of weed distributions in agricultural fields. This review describes the technologies of site‐specific weed management (SSWM) systems, evaluates their ecological and economic benefits and gives a perspective for the implementation in practical farming. Sensor technologies including 3D cameras, multispectral imaging and Artificial Intelligence (AI) for weed classification and computer‐based decision algorithms are described in combination with precise spraying and hoeing operations. Those treatments are targeted for patches of weeds or individual weed plants. Cameras can also guide inter‐row hoes precisely in the centre between two crop rows at much higher driving speed. Camera‐guided hoeing increased selectivity and weed control efficacy compared with manual steered hoeing. Robots combine those guiding systems with in‐row hoeing or spot spraying systems that can selectively control individual weeds within crop rows. Results with patch spraying show at least 50% saving of herbicides in various crops without causing additional costs for weed control in the following years. A challenge with these technologies is the interoperability of sensing and controllers. Most of the current SSWM technologies use their own IT protocols that do not allow connecting different sensors and implements. Plug & play standards for linking detection, decision making and weeding would improve the adoption of new SSWM technologies and reduce operational costs. An important impact of SSWM is the potential contribution to the EU‐Green Deal targets to reduce pesticide use and increase biodiversity. However, further on‐farm research is needed for integrating those technologies into agricultural practice.
New approaches to manage Asian soybean rust (Phakopsora pachyrhizi) using Trichoderma spp. or their antifungal secondary metabolites
(2022) El-Hasan, Abbas; Walker, Frank; Klaiber, Iris; Schöne, Jochen; Pfannstiel, Jens; Voegele, Ralf T.
Attempts have been made to determine the in vitro and in planta suppressive potential of particular Trichoderma strains (T16 and T23) and their secondary metabolites (SMs) against Asian soybean rust (ASR) incited by Phakopsora pachyrhizi. Aside from the previously identified SMs 6-pentyl-α-pyrone (6PAP) and viridiofungin A (VFA), the chemical structures of harzianic acid (HA), iso-harzianic acid (iso-HA), and harzianolide (HZL) were characterized in this study. Our results indicate that exposure of urediospores to 200 ppm 6PAP completely inhibits germination. A slightly higher dosage (250 ppm) of HZL and VFA reduces germination by 53.7% and 44%, respectively. Germ tube elongation seems more sensitive to 6PAP than urediospore germination. On detached leaves, application of conidia of T16 and T23 results in 81.4% and 74.3% protection, respectively. Likewise, 200 ppm 6PAP recorded the highest ASR suppression (98%), followed by HZL (78%) and HA (69%). Treatment of undetached leaves with 6PAP, HA, or HZL reduces ASR severity by 84.2%, 65.8%, and 50.4%, respectively. Disease reduction on the next, untreated trifoliate by T23 (53%), T16 (41%), HZL (42%), and 6PAP (32%) suggests a translocation or systemic activity of the SMs and their producers. To our knowledge, this study provides the first proof for controlling ASR using antifungal SMs of Trichoderma. Our findings strongly recommend the integration of these innovative metabolites, particularly 6PAP and/or their producers in ASR management strategies.

Browse

Recent Submissions