Background: Owing to their unique physiochemical properties, low toxicity, antipathogenic effects and tunability, fluorescent carbon quantum dots (CQDs) represent a new generation of carbon-based nanomaterials. Despite the mounting research on the efficacy of CQDs against resilient plant pathogens, their potential ability to mitigate viral pathogens and the underlying molecular mechanism(s) remain understudied. In this study, we optimized the CQDs to maximize their antiviral effects against a highly pathogenic Begomovirus (cotton leaf curl Multan virus, CLCuMuV) and elucidated the mechanistic pathways associated with CQDs-mediated viral inhibition. To fine-tune the CQDs-induced antiviral effects against CLCuMuV and investigate the underlying molecular mechanisms,we used HR-TEM, XRD, FT-IR, XPS, and UV‒Vis spectrophotometry to characterize the CQDs. SPAD and FluorCam were used for physiological and photosynthetic performance analysis. Transcriptome, RT‒qPCR, integrated bioinformatics and molecular biology were employed to investigate gene expression, viral quantification and data validation. Results: The application of fluorescent, hexagonal crystalline, UV-absorptive and water-soluble CQDs (0.01 mg/ml) significantly reduced the CLCuMuV titer and mitigated viral symptoms in N. benthamiana at the early (5 dpi) and late (20 dpi) stages of infection. CQDs significantly increased the morphophysiological properties, relative chlorophyll contents and photosynthetic (Fv/Fm, QY_max, NPQ and Rfd) performance of the CLCuMuV-infected plants. While CLCuMuV infection disrupted plant immunity, the CQDs improved the antiviral defense response by regulating important immunity-related genes involved in endocytosis/necroptosis, Tam3-transposase, the ABC transporter/sphingolipid signaling pathway and serine/threonine protein kinase activities. CQDs potentially triggered TSS and TTS alternative splicing events in CLCuMuV-infected plants. Conclusions: Overall, these findings underscore the antiviral potential of CQDs, their impact on plant resilience, and their ability to modulate gene expression in response to viral stress. This study’s molecular insights provide a foundation for further research on nanomaterial applications in plant virology and crop protection, emphasizing the promising role of CQDs in enhancing plant health and combating viral infections. Graphical

Potato leafroll virus (PLRV) is a widespread and one of the most damaging viral pathogens causing significant quantitative and qualitative losses in potato worldwide. The current knowledge of the geographical distribution, standing genetic diversity and the evolutionary patterns existing among global PLRV populations is limited. Here, we employed several bioinformatics tools and comprehensively analyzed the diversity, genomic variability, and the dynamics of key evolutionary factors governing the global spread of this viral pathogen. To date, a total of 84 full-genomic sequences of PLRV isolates have been reported from 22 countries with most genomes documented from Kenya. Among all PLRV-encoded major proteins, RTD and P0 displayed the highest level of nucleotide variability. The highest percentage of mutations were associated with RTD (38.81%) and P1 (31.66%) in the coding sequences. We detected a total of 10 significantly supported recombination events while the most frequently detected ones were associated with PLRV genome sequences reported from Kenya. Notably, the distribution patterns of recombination breakpoints across different genomic regions of PLRV isolates remained variable. Further analysis revealed that with exception of a few positively selected codons, a major part of the PLRV genome is evolving under strong purifying selection. Protein disorder prediction analysis revealed that CP-RTD had the highest percentage (48%) of disordered amino acids and the majority (27%) of disordered residues were positioned at the C-terminus. These findings will extend our current knowledge of the PLRV geographical prevalence, genetic diversity, and evolutionary factors that are presumably shaping the global spread and successful adaptation of PLRV as a destructive potato pathogen to geographically isolated regions of the world.

Radermachera sinica (China doll) is a popular evergreen horticultural crop worldwide. However, little information has been provided to describe the anthracnose disease of R. sinica. In 2018, symptoms suspected of leaf anthracnose were observed on R. sinica in gardens and commercial greenhouses in Guangzhou, China. Lesions on diseased leaves showed thinned and grayish white centers, dark-brown to black borders, and raised black spots. Twenty-seven single-conidia isolates were obtained from symptomatic leaf lesions. Based on morphological characteristics and multilocus phylogenetic analysis, 19 isolates were identified as Colletotrichum siamense and six and two isolates were identified as C. fructicola and C. karstii, respectively. An in vivo pathogenicity test was conducted on leaves of R. sinica plants, and it was discovered that C. siamense was more aggressive under wounded conditions than under unwounded conditions, and caused symptomatic necrotic lesions on the leaf. Afterward, the same pathogen was reisolated from lesions of inoculated leaves to fulfill Koch’s postulates. However, neither C. fructicola nor C. karstii caused visible lesions on leaves of R. sinica under wounded or unwounded conditions, indicating that they may be asymptomatic endophytes or opportunistic pathogens on R. sinica. To our knowledge, this study is the first report of Colletotrichum spp. associated with anthracnose disease on R. sinica in China.