Publications

4815

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.

Background: Ticks are significant vectors of pathogens, and their nonpathogenic intracellular bacteria, known as endosymbionts, influence tick physiology and may interact with tick-borne pathogens. Such relationships can affect transmission dynamics and understanding them is essential for designing strategies that control tick-borne diseases and reduce their impact on human and animal health. Aim: This study aimed to determine the prevalence and density of two key endosymbiotic bacteria, Francisella-like endosymbiont (FLE) and Candidatus Midichloria mitochondrii (Ca. M. mitochondrii), and to investigate possible correlations between these symbionts and the protozoan parasite Theileria annulata in Hyalomma anatolicum ticks. Methods: Between January and October 2024, 116 ticks were collected from cattle in the Diwaniyah province, Iraq. The morphological examination was followed by molecular confirmation using mitochondrial 16S rRNA sequencing. Quantitative polymerase chain reaction was applied to detect and quantify FLE, Ca. M. mitochondrii, and T. annulata in H. anatolicum. Results: H. anatolicum was the predominant species, representing 86% of ticks, whereas H. excavatum accounted for 13%. Mitochondrial 16S rRNA sequences confirmed species identity and showed 99.48-100% similarity to reference isolates from China, Pakistan, Turkey, India, and Russia. FLE was detected in 100% of H. anatolicum, with mean loads of 7.9× 103 copies per tick. Ca. M. mitochondrii was detected in 99% of specimens, with mean loads of 3.7×102 copies per tick. FLE densities tended to be higher in females compared to males (9.7 × 10³ copies vs. 1.8 × 10³ copies) but difference was not statistically significant. Ca. M. mitochondrii loads also differed significantly (4.8 × 10² copies vs. 1.3 × 10¹ copies). T. annulata was present in all ticks, with the highest copy numbers in semi-engorged females (1.9 × 104 copies), followed by males (2.8 × 10³ copies). Our findings revealed a statistically significant association (p<0.05) between T. annulata and Ca. M. mitochondrii, whereas no significant correlation was observed between T. annulata and FLE. Conclusion: The presence of FLE and Ca. M. mitochondrii in H. anatolicum from the Diwaniyah province was documented. Evidence indicated associations between symbiont density and T. annulata infection, and the results point toward a possible role of endosymbiotic bacteria in pathogen persistence and the epidemiology of tick-borne diseases.

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.