Yuhan Zhang

A sensitive and reliable analytical method based on ultra-high performance liquid chromatography–tandem mass spectrometry (UHPLC-MS/MS) was developed and validated for the simultaneous determination of bifenazate, cyflumetofen, etoxazole, and abamectin B_1a in citrus leaves, whole fruit, peel, and pulp. The method exhibited good linearity (0.0001–0.1 mg/L, R² > 0.999), a limit of quantification (LOQ) of 0.001 mg/kg, mean recoveries of 77.3–110.5%, and relative standard deviations of 3.1–19.8%. This method was applied to compare the dissipation dynamics and dietary risks of the four acaricides following knapsack spraying versus unmanned aerial vehicle (UAV) spraying. Compared to knapsack application, UAV spraying resulted in 2.2- to 4.1-fold higher initial deposits on citrus leaves and shorter dissipation half-lives. After 21 days, all terminal residues were below the maximum residue limits (MRLs) established by China, the Codex Alimentarius Commission, the United States, Australia, Korea, the European Union, and Japan. Chronic dietary risk assessment revealed risk quotients below 1% for cyflumetofen and etoxazole, and approximately 47% for bifenazate and 93% for abamectin B_1a. Although all values were below the acceptable threshold of 100%, the risk for abamectin B_1a approached this limit, indicating that its cumulative dietary risk should not be overlooked. This study provides scientific evidence for residue monitoring of acaricides in citrus and for the safety evaluation of UAV-based pesticide application.

Pepper blight, caused by Phytophthora capsici, significantly impacts plant health and reduces crop yields, resulting in severe economic losses. Developing resistant varieties and identifying resistance targets through transcriptomic sequencing, along with elucidating their underlying resistance mechanisms, represent pivotal strategies for disease control. In this study, 11 resistant pepper varieties were identified from 21 varieties; among these, the highly resistant line 19K23 and the susceptible line QM were selected for further analysis. Transcriptome sequencing of root samples from both varieties was conducted on day 2 and day 5 after inoculation with P. capsici. Analysis of differentially expressed genes between the resistant variety and susceptible variety revealed pathways such as photosynthesis, oxidoreductase activity, plant-pathogen interaction, and secondary metabolism. Six key biological processes were highlighted among the highly differentially expressed genes, with porphyrin and chlorophyll metabolism activated early in 19K23. The Ras family, MAPK signaling, hormone signal transduction, and GPI-anchor biosynthesis were implicated in resistance. Importantly, secondary metabolism and lipid metabolism pathways such as phenylpropanoid biosynthesis, isoquinoline alkaloid biosynthesis, and unsaturated fatty acid biosynthesis appeared to play pivotal roles. Additionally, cell wall synthesis and structure, as well as stress response processes, were important. These findings enhance understanding of pepper resistance mechanisms against P. capsici and offer valuable molecular insights for future research on genetic regulation and resistance breeding.

Fusarium head blight (FHB), caused by the fungal pathogen Fusarium graminearum, is a destructive disease worldwide. Ascospores are the primary inoculum of F. graminearum, and sexual reproduction is a critical step in its infection cycle. In this study, we characterized the functions of FgCsn12. Although the ortholog of FgCsn12 in budding yeast was reported to have a direct interaction with Csn5, which served as the core subunit of the COP9 signalosome, the interaction between FgCsn12 and FgCsn5 was not detected through the yeast two-hybrid assay. The deletion of FgCSN12 resulted in slight defects in the growth rate, conidial morphology, and pathogenicity. Instead of forming four-celled, uninucleate ascospores, the Fgcsn12 deletion mutant produced oval ascospores with only one or two cells and was significantly defective in ascospore discharge. The 3′UTR of FgCsn12 was dispensable for vegetative growth but essential for sexual reproductive functions. Compared with those of the wild type, 1204 genes and 2240 genes were up- and downregulated over twofold, respectively, in the Fgcsn12 mutant. Taken together, FgCsn12 demonstrated an important function in the regulation of ascosporogenesis in F. graminearum.