Host Range Test for the Pathogens of Tobacco Bushy Top Disease in Yunnan

Tobacco bushy top disease (TBTD) is a complex disease caused by mixed infection of Tobacco bushy top virus(TBTV), Tobacco vein distorting virus(TVDV), satellite RNA of TBTV (Sat-TBTV) and/or Tobacco vein distorting virus associate RNA(TVDVaRNA).Twelve plant species were used to test the host range of TBTD pathogens by viruliferous aphid transmission for 15 days. The inoculated Solanaceae spp. plants such as Capsicum annuum and Physalis alkekengi showed chlorosis, yellowing and shrinking on the leavies, however, no distinct symptom was observed on the inoculated plants such as Cucumis sativus and Phaseolus vulgaris. The TBTD pathogens were then tested by RT-PCR and results showed that six Solanaceae spp. plants including P. alkekengi, Nicandra physaloides, Datura stramonium, Lycopersicon esculentum, Petunia hybrida and C. annuum could be infected by all of the four TBTD pathogens. However, only one to three TBTD pathogens could infect the other tested plants such as C. sativus, Cucurbita pepo, Chenopodium quinoa, Vigna unguiculata, P. vulgaris and Brassica campestris. TVDV could be detected with the highest ratio of 83.3%, suggesting that TVDV plays very important roles in disease cycle. The results also indicated that some of the TBTD pathogens could be separated from some tested host plants with the aphid transmission way, it would be beneficial to studying the functions of different TBTD pathogens in disease symptoms formation and disease transmission. The results also offer some valuable information for the studies on other complex plant disease co-infected by different virus pathogens.