Preliminary Studies on Species and Distribution of Citrus Viroids in China

Citrus viroids are the small but economically important RNA pathogens. For investigating their occurrence and distribution in China, 65 viroid samples collected from 8 major citrus cultivated regions were evaluated using one-step or multiplex one-step RT-PCR and biological indexing for specifically detection of Citrus exocortis viroid (CEVd), Citrus bent leaf viroid (CBLVd), Hop stunt viroid (HSVd), Citrus viroid-III (CVd-III) and Citrus viroid-IV (CVd-IV). The results showed that there were at least 4 kinds of citrus viroids (CEVd, CBLVd, HSVd, and CVd-III) on citrus trees in China. Most of the infected citrus plants harbored more than one viroid species, and two plants were infected with up to 4 citrus viroids. Sweet orange was more frequently infected by viroids than other citrus varieties. It is the preliminary report on the species and distribution of citrus viroids in China.