Publications

4372

Abstract BACKGROUND Huanglongbing (HLB) is the most devastating citrus disease worldwide, with no resistant commercial citrus varieties identified and no effective chemical treatments currently available on the market. The main challenge in developing effective strategies for controlling HLB is the inability to culture its associated pathogen, the fastidious Candidatus Liberibacter asiaticus ( C Las), in defined media or axenic cultures. RESULTS In this study, we developed an effective method for screening antimicrobials against C Las using periwinkle as a model plant. Compared with citrus, periwinkle offers notable advantages, including reduced time, increased efficiency, and lower costs. This method consists of two main components: screening exogenously applied antimicrobials and evaluating overexpressed endogenous antimicrobial peptides. Using this method, we demonstrated that bromothalonil and cyproconazole effectively inhibit the proliferation of C Las in hydroponically grown periwinkle. Further analyses revealed that bromothalonil and cyproconazole were also highly toxic to other citrus pathogens, including Xanthomonas citri subsp. citri ( Xcc ), Alternaria alternata tangerine pathotype (Z7), and Penicillium digitatum (KH8). In addition, we established an Agrobacterium rhizogenes ‐mediated hairy root genetic transformation system for periwinkle and demonstrated that the proliferation of C Las was significantly inhibited in transgenic roots overexpressing antimicrobial peptide (SAMP). CONCLUSION An efficient antimicrobial screening system for C Las and several other citrus pathogens has been established. By addressing challenges such as high costs, prolonged experimental periods, and heavy workloads, we anticipate that this developed method will serve as a useful tool for the identification of antimicrobials effective against C Las and other citrus pathogens. © 2025 Society of Chemical Industry.

First sugar beet varieties with reasonable yield stability under infection with Candidatus Arsenophonus phytopathogenicus (ARSEPH), the causal agent of the syndrome “Basses Richesses” (SBR), were discovered, but the mechanisms behind this have not been described yet. Thus, this research aimed at analyzing different morphological, physiological and quality related traits of ARSEPH infected sugar beet taproots to identify methods for SBR variety screening. In a greenhouse experiment, one susceptible and two tolerant varieties were infected with ARSEPH via the vector Pentastiridius leporinus (reed glass-winged cicada) under controlled conditions. In the susceptible variety, an infection with ARSEPH caused an average reduction in volume (~40%), length (~6%), width (~21%), fresh mass (~41%) and an increase in dry matter content (~5%). The tolerant varieties exhibited a lower effect on these parameters but showed a greater increase in alcohol insoluble residues (cellulose, hemicellulose, pectin, lignin) and marc content. The significant enhancement in flexural taproot tissue strength observed in the tolerant varieties may be linked to increased levels of structural cell components. The susceptible and one tolerant variety exhibited reduced periderm puncture resistance after infection. This first study of physiological and morphological traits provides deeper insights into host-pathogen interaction and potential variety response. To confirm the relevance and implications of the results as new parameters for screening of SBR-tolerant varieties, further analysis with additional varieties across a larger number of samples is necessary.