Phytoplasma-Induced Leaf Reddening as a Monitoring Symptom of Apple Proliferation Disease with Regard to the Development of Remote Sensing Strategies

Apple proliferation (AP) is an economically important disease in many apple-growing regions caused by ‘Candidatus Phytoplasma mali’ which is spread by migrating psyllid vectors on a regional scale. As infected trees in orchards are the only inoculum source, the early eradication of those trees is one of the most efficient strategies to prevent further spread of AP. Remote sensing is a promising rapid and cost-effective tool to identify infected trees on a regional scale. AP-induced premature leaf reddening was evaluated as a reliable symptom for remote sensing by monitoring more than 20,000 trees in 68 different orchards with 20 representative cultivars from 2019 to 2022 in a highly AP-affected region in Southwest Germany. Specific AP symptoms were almost 100% correlated with molecular detection of ‘Ca. P. mali’ and these specific symptoms were almost 100% correlated with leaf reddening. ‘Ca. P. mali’ was detected in 71–97% of trees which showed partial or entire reddening without any other AP symptom. Experimental and field data showed that reddening was induced by cold night and warm day temperatures (about 5 °C vs. 20 °C) in September. Quantification of the phytoplasma by real-time PCR showed no correlation with the intensity of reddening in the leaf. PCR-RFLP subtyping revealed no influence of different ‘Ca. P. mali’ strains on the symptom expression. In conclusion, leaf reddening in late September/early October was a reliable symptom useful for remote sensing of AP

Entwicklung von Methoden zum Monitoring der Flavescence dorée und zur Abschätzung der Risiken für den deutschen Weinbau durch autochthone Wirtspflanzen als potenzielle Infektionsquellen in Verbindung mit der Ausbreitung des Vektors Scaphoideus titanus

Im Rahmen des Projektes FLAVEPREVENT wurden Methoden zur zuverlässigen Diagnose und Charakterisierung der Erreger der Quarantänekrankheit Flavescence dorée (FD) in Reben, alternativen Wirtspflanzen und potentiellen Vektoren etabliert und in Hinblick auf ihre Anwendung durch die Rebschutzdienste in Deutschland evaluiert. Mithilfe innovativer Monitoringstrategien wurden Infektionsrisiken für Reben abgeschätzt, die von mit FDverwandten Phytoplasmen infizierten wilden Wirtspflanzen ausgehen. Die Verbreitung von FD-verwandten Phytoplasmen in den wichtigsten deutschen Weinbaugebieten wurde beschrieben und die epidemiologische Rolle alternativer Übertragungswege durch authochthone Reservoirpflanzen und potentielle Vektorarten wurde untersucht. Die zielgerichtete Anwendung der erarbeiteten Erkenntnisse führte zur Früherkennung des ersten FD-infizierten Rebstocks in einer Erwerbsanlage in Deutschland. Die Ergebnisse wurden in einer praktischen Anleitung zum Monitoring und zur Diagnostik der FD zusammengefasst und die Detektion des ersten FD-infizierten Rebstocks wurde als Disease Note in Plant Disease veröffentlich

Risk Assessment for the Spread of Flavescence Dorée-Related Phytoplasmas from Alder to Grapevine by Alternative Insect Vectors in Germany

“Flavescence dorée” (FD)-related phytoplasmas are widespread in alder in Germany and their transmission to grapevine represents a high risk for FD outbreaks when the primary vector, Scaphoideus titanus, becomes present in the future. Therefore, the potential role of the Deltocephalinae leafhopper species in transmitting FD-related phytoplasmas from alder to grapevine was studied in extensive transmission trials conducted between 2017 and 2020. The transmission capacity of autochthonous Allygus spp. and the invasive Orientus ishidae captured on infected alder trees was tested under controlled conditions using various test designs, including grouped insects and single-insect studies. The latter experiments were analyzed in terms of survival probability, transmission success and phytoplasma load in the insects, measured by quantitative PCR. A minimum inoculation titer (MIT) required for successful transmission to alder was defined for both Allygus spp. and O. ishidae. While Allygus spp. exhibited slightly better survival on Vitis vinifera compared to O. ishidae, the latter displayed higher phytoplasma loads and greater transmission success. Although all species were capable of infecting alder seedlings, O. ishidae was able to transmit 16SrV-phytoplasmas directly to single grapevines. Infective adults of O. ishidae were captured from the beginning of July until the end of August, while Allygus spp. were only considered infective towards the end of the season. Thus, O. ishidae likely poses a higher risk for FD transmission from alder to grapevine, albeit at a very low level, as only five out of 90 transmission trials to V. vinifera were successful

Diseases and insect vectors

Diseases and insect vector

Diseases and insect vectors

Diseases and insect vector

Study of the epidemiology of “flavescence dorée”(FD)-related phytoplasmas and potential vectors in a FD-free area

International audienc

Detection of Two Different Grapevine Yellows in Vitis vinifera Using Hyperspectral Imaging

Grapevine yellows (GY) are serious phytoplasma-caused diseases affecting viticultural areas worldwide. At present, two principal agents of GY are known to infest grapevines in Germany: Bois noir (BN) and Palatinate grapevine yellows (PGY). Disease management is mostly based on prophylactic measures as there are no curative in-field treatments available. In this context, sensor-based disease detection could be a useful tool for winegrowers. Therefore, hyperspectral imaging (400–2500 nm) was applied to identify phytoplasma-infected greenhouse plants and shoots collected in the field. Disease detection models (Radial-Basis Function Network) have successfully been developed for greenhouse plants of two white grapevine varieties infected with BN and PGY. Differentiation of symptomatic and healthy plants was possible reaching satisfying classification accuracies of up to 96%. However, identification of BN-infected but symptomless vines was difficult and needs further investigation. Regarding shoots collected in the field from different red and white varieties, correct classifications of up to 100% could be reached using a Multi-Layer Perceptron Network for analysis. Thus, hyperspectral imaging seems to be a promising approach for the detection of different GY. Moreover, the 10 most important wavelengths were identified for each disease detection approach, many of which could be found between 400 and 700 nm and in the short-wave infrared region (1585, 2135, and 2300 nm). These wavelengths could be used further to develop multispectral systems

Differenz durch Normalisierung

Der Autor hinterfragt, „welche Wirkungen implizite (und explizite) Normalitätsvorstellungen in der Erziehungswissenschaft auf den Umgang mit bzw. auf die Produktion von Gleichheit und Differenz haben. Da Normalisierung als Begriff inzwischen relativ weit verbreitet ist, hat er unterschiedliche Bedeutungen und, je nach Kontext, abweichende Konnotationen (1.). Um diese zu verstehen, lohnt ein Blick in die Entstehungsgeschichte heute wirksamer Vorstellungen von Normalität (2.). Am Beispiel von Rousseaus Émile wird angedeutet, wie (überholte) Normalitätsvorstellungen in pädagogischen Theorien auch heute (noch) unbedacht etwa auf das pädagogische Menschenbild wirken können (3.). Darüber hinaus kann man z. B. Aspekte der jüngeren Subdisziplinbildung der Erziehungswissenschaft als Resultat der normalisierenden Wirkung pädagogischer Theorien begreifen (4.) (…) Anhand einer Diskussion aus einem Teilbereich der Interkulturellen Erziehungswissenschaft, der Frage der Ethnisierung durch ethnisch orientierte wissenschaftliche Erklärungsansätze, wird angedeutet, dass Normalisierungen im Bildungswesen mehr als rein akademische Folgen haben (5.). Insgesamt zeigt die Argumentation – wenn an dieser Stelle auch nur skizzenhaft –, dass Normalisierungsprozesse auch in der Erziehungswissenschaft durch die Verbreitung bestimmter Normalitätsannahmen Differenz bzw. Differenzvorstellungen erzeugen bzw. verstärken.“ (DIPF/ Orig./ ssch