Citrus yellow mottle-associated virus (CiYMaV) belonging to the subgenus Mandarivirus within the genus Potexvirus, was first identified in 2018 from Pakistan (CiYMaV-PK), where it is endemic in several regions.  Here, three full-length cDNA clones (pCiYMaV-FL-1, pCiYMaV-FL-18, and pCiYMaV-FL-22) corresponding to the genomic RNA of CiYMaV were constructed and then agroinfiltrated on Chandler pummelo (Citrus grandis) seedlings using the vacuum infiltration method.  All the inoculated plants developed severe vein yellowing, leaf mottling, and dwarfing symptoms by 40 days post-infiltration (dpi).  The results of a direct tissue blot immunoassay and reverse transcription polymerase chain reaction detection showed 94.7–100% infection rates of pCiYMaV-FL at 60 dpi.  Despite there being no observed difference among the three clones in the severity of symptom, pCiYMaV-FL-22 showed the highest accumulation levels of viral RNA and coat proteins.  Moreover, pCiYMaV-FL-22 successfully infected seven other citrus varieties and induced symptoms in five of them.  Transmission electron microscopy identified the presence of filamentous virus particles in extracts from systemic leaves of the plants infected with pCiYMaV-FL-22 at 6-months post-infiltration.  Taken together, the results indicate that Koch’s postulates were fulfilled for CiYMaV in citrus plants.  This is the first report of full-length infectious cDNA clones of CiYMaV, and thus, the data provide a basis for further study of the molecular mechanisms of virus infection and the development of a viral vector to express foreign genes in citrus plants.

Zinc (Zn) deficiency is widespread among citrus plants, but information about the mechanisms for Zn deficiency response in these plants is scarce. In the present study, different navel orange (Citrus sinensis (L.) Osbeck) leaves with various yellowing levels were sampled in our experimental orchard, and upon estimation of nutrient contents, Zn deficiencies were diagnosed as mild, moderate, and severe. Further analysis of chlorophyll content, photosynthetic characteristics, antioxidant enzyme activities, and expression levels of Zn/Iron-regulated transporter-like protein (ZIP) family genes were conducted in the sampled Zn-deficient leaves. The results showed that chlorophyll contents and net photosynthetic rate (P_n) seemed to decrease with reduced Zn contents. In addition, comparison of severe Zn-deficient and normal leaves revealed that activities of peroxidase (POD) and catalase (CAT) increased significantly, whereas that of Zn-containing enzymes such as Cu/Zn superoxide dismutase (Cu/Zn-SOD) significantly reduced with decreasing Zn contents. As expected, expression of the ZIP family genes, ZIP1, ZIP3, and ZIP4, was induced by Zn deficiencies. These results deepen our understanding of Zn deficiency in citrus plants as well as provide useful preliminary information for further research.