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Abstract: In March 2021, unusual plant stuning, collar, and wet root rot of lettuce (Lactuca sativa L.) during the rosette stage was observed in two commercial fields in Serbia (44°58'N, 20°32'E; 44°45'N, 20°43'E). Disease incidence in the fields (≈ 0.9 ha each) was approximately 15 and 20%, respectively. Initial above-ground symptoms were yellowing and wilting of leaves, while below-ground symptoms were collar, wet root rot, and lesions becoming necrotic. Eventually, whole plants wilted, collapsed, and died. A total of 35 symptomatic plants were collected from the fields, and diseased tissues were cut into small pieces, surface sterilized, and plated on potato dextrose agar (PDA). Isolation resulted in 20 morphologically uniform monoconidial isolates. The isolates formed white to creamy colonies, gradually becoming salmon pink, slimy, or moist in appearance, with sparse aerial mycelia. Numerous hyphal coils with conidiophores and hyaline, smooth-surfaced, ellipsoid to ovoid, septate or aseptate conidia were formed (4.5 to 10.1×1.2 to 3.7 μm (n = 100)). To confirm the species identity, the internal transcribed spacer (ITS) region and the D1/D2 region of a selected representative isolate 13-3-c were amplified and sequenced by using primer pairs ITS1/ITS4 (White et al. 1990) and N1/N2 (O’Donnell and Gray 1995), respectively. The sequences were deposited in GenBank (ITS: OR880564 and D1/D2: OR880567). Sequence analysis revealed 100% nucleotide identity with P. cucumerina isolates from different countries deposited in the NCBI GenBank, including isolate MH860704 (Vu et al. 2019) (ITS region) and isolate KY662256 (Su et al. 2017) (D1/D2 region). Neighbor-joining analysis was conducted based on the combined ITS and D1/D2 regions, and the tree was constructed with the substitution models (1,000 bootstrap). The combined phylogeny confirmed that the sequences shared a common clade with P. cucumerina. Hence, morphological, microscopic, and molecular characterization confirmed the pathogen as P. cucumerina (Palm et al., 1995; Carlucci et al., 2012). In a pathogenicity assay, 10 isolates were tested. Five 30-day-old lettuce plants (cv. Majska Kraljica) per isolate were root-dipped in the conidial suspensions (1×105 conidia/ml). The 10 inoculated plants were transplanted into 1 L pots containing sterile substrate (Floragard, Germany). Plants treated with sterile distilled water were used as controls. Plants were maintained in a greenhouse at 25 to 28°C under a 12-hour photoperiod (Cai et al., 2021). Four weeks after inoculation, stunting, chlorosis, and wilting of plants were observed, while collars and roots exhibited typical decaying symptoms. No symptoms were observed on the control plants. The pathogen was reisolated from symptomatic tissue as previously described. Koch's postulates were completed by confirming the identity of reisolates based on morphological features. To our knowledge, this is the first report of P. cucumerina on lettuce or any other crop in Serbia. P. cucumerina is already known as a pathogen of lettuce and other hosts grown in many countries worldwide, as well as in some European countries (Belgium, England, Italy, the Netherlands, and Switzerland) (Zhang et al. 2019). This emerging pathogen may cause significant economic losses in lettuce production in Serbia and in the entire Balkan region. Our results may help to develop effective management strategies based on accurate and timely identification and regular pathogen monitoring.
Keywords: detection, identification, salat, plant diseases
Published in DiRROS: 17.05.2024; Views: 30; Downloads: 11
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Abstract: The genus Agrilus is one of the most diverse insect genera worldwide. The larval feeding activity causes extensive damage in both forests and orchards. In addition, more than 30 species have been introduced outside their native range so far, including the emerald ash borer Agrilus planipennis Fairmaire. Thus, the availability of efficient trapping protocols for early detection of Agrilus species at entry points is of utmost importance. In this study we tested whether trapping protocols developed for surveillance of A. planipennis in North America were also effective for other Agrilus species. In particular, through a multi-country assessment we compared the efficacy of detecting Agrilus species on: (i) green glue-coated prism traps vs. green Fluon-coated multi-funnel traps when baited with the green leaf volatile (Z)-3-hexenol or left unbaited; and (ii) green multi-panel traps vs. green multi-panel traps baited with dead adult Agrilus beetles (decoys). A total of 23,481 individuals from 45 Agrilus species were caught. Trap design significantly affected both species richness and abundance of Agrilus species in several of the countries where the trapping experiments were carried out, and green prism traps outperformed green multi-funnel traps in most cases. On the contrary, the addition of a (Z)-3-hexenol lure or dead adult beetle decoys on to traps did not improve trap catches. Our study highlights that reliable trap models to survey Agrilus species are already available, but also that there is the clear need to further investigate chemical ecology of Agrilus species to develop semiochemical lures that can improve detection efficacy.
Keywords: biosecurity, early detection, forest pests, lures, traps, visual stimuli, Agrilus, beetles
Published in DiRROS: 19.01.2024; Views: 232; Downloads: 184
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Abstract: Early detection is important for the management of invasive alien species. In the last decade citizen science has become an important source of such data. Here, we used opportunistic records from the “LIFE ARTEMIS” citizen science project, in which people submitted records from places where they observed tree pests, to understand the distribution of a rapidly-spreading forest pest: the oak lace bug (Corythucha arcuata) in Slovenia. These citizen science records were not distributed randomly. We constructed a species distribution model for C. arcuata that accounted for the biased distribution of citizen science by using the records of other tree pests and diseases from the same project as pseudo-absences (so-called constrained pseudo-absences), and compared this to a model with pseudo-absences selected randomly from across Slovenia. We found that the constrained pseudo-absence model showed that C. arcuata was more likely to be found in east, in places with more oak trees and at lower elevations, and also closer to highways and railways, indicating introduction and dispersal by accidental human transport. The outputs from the model with random pseudo-absences were broadly similar, although estimates from this model tended to be higher and less precise, and some factors that were significant (proximity to minor roads and human settlements) were artefacts of recorder bias, showing the importance of taking the distribution of recording into account wherever possible. The finding that C. arcuata is more likely to be found near highways allows us to design advice for where future citizen science should be directed for efficient early detection.
Keywords: Oak lace bug, ecological modelling, citizen science, invasive alien species, early detection, Corythucha arcuata
Published in DiRROS: 08.09.2022; Views: 526; Downloads: 265
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