Publications

4857

Abstract The pear psyllid Cacopsylla pyri is the main vector of ‘ Candidatus Phytoplasma pyri’, the causal agent of pear decline, a disease associated with severe yield losses in pear production. Phytoplasmas are further known to interfere with their vectors metabolism; therefore, we investigated whether an infection with ‘ Ca. P. pyri’ is associated with changes in nutrient storage of the pear psyllids. Additionally, we measured whether the phytoplasma infection is associated with differences in flight performance in C. pyri , as the flight activity of the vector is a key component of phytopathogen spread. Using a flight mill, we quantified flight distance, duration, and speed, and combined qPCR-based infection detection with colorimetric assays to determine protein, carbohydrate, and lipid content from the same individual. Infected psyllids contained significantly higher levels of soluble carbohydrates than uninfected individuals. Lipid content was not affected by the phytoplasma infections but was found to be consistently higher in males than in females, while protein levels did not vary with sex or infection status. Despite infection-related differences in carbohydrate levels, phytoplasma infection did not significantly affect flight duration, distance, or speed. These results indicate that infection-associated shifts in bulk carbohydrate storage do not translate into altered flight motivation or performance, suggesting a functional decoupling between metabolic state and realised dispersal capacity under standardised laboratory conditions.

Abstract Since 2025, EFSA has conducted expert knowledge elicitations to estimate survey parameters for the detection of EU priority pests listed in Commission Delegated Regulation (EU) 2019/1702, in cases where pest‐specific information is lacking in the scientific literature. The design and implementation of statistically sound and risk‐based surveys require quantitative parameters such as sampling effectiveness, design prevalence and relative risk. This report presents the estimated values for Bactericera cockerelli and ‘Candidatus Liberibacter solanacearum’, together with the supporting evidence and expert rationale. These values will be integrated into the EFSA Plant Pest Survey Toolkit to guide EU Member States in designing harmonised pest surveys across the EU.

ABSTRACT Leptothrix mechoopdaensis BB-3 and BB-4 are metal-oxidizing, sheathed, filamentous bacteria that were isolated from a woodland iron seep near Centerville, Chico, CA, USA. Here, we report a closed circular genome sequence for each strain, assembled from reads sequenced on an Oxford Nanopore FLO-MIN114 flow cell.

Citrus greening disease, also known as huanglongbing (HLB), is caused by the gram-negative α-proteobacteria Candidatus Liberibacter species. This disease poses a significant threat to citrus production worldwide, including in Nepal. This study aimed to perform the diagnosis and phylogenetic analysis of the citrus greening pathogen in Nepal using both conventional PCR and computational methods. A total of 1,026 citrus leaf samples were collected from thirteen districts across six provinces in the country. PCR-based diagnosis was performed using the primer set Las606/LSS, which targets the 16S rRNA gene of Candidatus Liberibacter asiaticus. The reliability of the PCR was validated by including previously confirmed positive and negative controls in every run. Furthermore, each assay was performed in triplicate to ensure consistency and reproducibility of results. Additionally, 16S rRNA gene sequencing was performed using Sanger sequencing for five samples. The obtained sequences were deposited in GenBank and a phylogenetic tree was constructed based on these sequences. Among the 1,026 samples tested, 255 were positive, indicating the widespread distribution of HLB across Nepal. All consensus sequences from Nepal showed strong evolutionary relatedness within the Ca. L. asiaticus cluster, with over 99% genetic similarity to reference sequences from various parts of the world. Phylogenetic analysis revealed that the Nepalese sequences were closely related to Ca . L. asiaticus sequences from India (Punjab and Meerut) and sequences obtained from different regions of Nepal clustered closely together. The molecular findings from this study reveal a high prevalence of citrus greening disease across Nepal and underscore the urgent need for integrated management policies, including the use of certified clean planting material and vector (psyllid) control programs. The generated sequence data serves as a vital resource for developing regional diagnostic tools and guiding future surveillance strategies to mitigate HLB’s impact on the world’s citrus industry.

Sugar beet cultivation in Europe is threatened by two vector-borne diseases: syndrome “basses richesses”, caused by the phloem-limited pathogen ‘Candidatus Arsenophonus phytopathogenicus’, and phytoplasmoses associated with ‘Ca. Phytoplasma solani’ subgroup 16SrXII-A and the related subgroup 16SrXII-P. Infections lead to reduced sugar yield, biomass and growth abnormalities. In Germany, Pentastiridius leporinus represents the main vector. Despite their importance, genetic diversity remains poorly understood. During a two-year survey, barcoded amplicons were generated from infected sugar beet samples from Germany and neighbouring countries using the phytoplasma markers 16S rRNA-ITS-23S rRNA, tuf, and groEL-stamp-nadE, as well as rplO-secY-rpmJ and groEL for ‘Ca. A. phytopathogenicus’. Amplicon pools underwent single-molecule real-time sequencing and amplicon-sequence-variant inference. Additionally, planthopper samples from sugar beet in Germany were analysed and compared to sugar beet data for ‘Ca. A. phytopathogenicus’. No genetic diversity of ‘Ca. A. phytopathogenicus’ was detected, whereas 16SrXII-A and -P showed variation below the subgroup level. 16SrXII-A exhibited higher diversity than 16SrXII-P. In Germany, 16SrXII-A formed a single cluster, while 16SrXII-P comprised two clusters based on 16S rRNA-ITS-23S rRNA. In neighbouring countries, only 16SrXII-A showed diversity, resolving up to four clusters by groEL-stamp-nadE. These results provide a basis for the identification of dominant strains supporting comparative variety evaluation for tolerance.