Etiology Of Ageratum Yellow Vein Disease In Yunnan And Guangxi Provinces

Ageratum conyzoides is a kind of common weed which can be infected by a great variety of plant viruses. A. conyzoides was also an important reservoir host and initial source for geminiviruses. To understand types of geminiviruses infecting A. conyzoides, research work was carried out to identify viruses infecting A. conyzoides plants in Yunnan and Guangxi provinces.A. conyzoides samples showing yellow vein symptom collected from Yunnan were mainly infected by Tobacco curly shoot virus (TbCSV) associated with Ageratum yellow vein China betasatellite (AYVCNB), Ageratum yellow vein China virus (AYVCNV) was not found in these samples. While samples from Guangxi were mostly infected by Papaya leaf curl China virus (PaLCuCNV) associated with AYVCNB. A few samples from Guangxi province were mixed infected by PaLCuCNV and AYVCNV, and only one sample was infected by unique AYVCNV. All samples were associated with AYVCNB.To ascertain how AYVCNB interacts with heterogenous TbCSV or PaLCuCNV and produces typical yellow vein symptoms without its homologous helper virus AYVCNV, the infectious clones were used to infect A. conyzoides by agroinoculation. The results showed that co-inoculation of TbCSV and AYVCNB, or PaLCuCNV and AYVCNB could infect A. conyzoides and produce typical yellow vein, leaf curling symptom. PCR and Southern blot confirmed the interaction of TbCSV/AYVCNB and PaLCuCNV/AYVCNB. Consequently, Ageratum yellow vein disease in Yunnan and Guangxi provinces were coused by begomovirus complexes TbCSV and AYVCNB or PaLCuCNV and AYVCNB.