Molecular Identification Of Begomoviruses Infecting Malvastrum Coromandelianum In Yunnan Province

Geminiviruses have been reported infecting crops and weeds such as tobacco, tomato,Malvastrum coromandelianum and Siegesbeckia orientalis and have caused significant yield losses in Yunnan Province.Weeds are important alternative hosts for geminiviruses.So research works were carried out to identify viruses infecting Malvastrum coromandelianum plants in Yunnan province.Isolate Y278 was collected from Malvastrum coromandelianum in Baoshan, Yunnan.The complete DNA-A sequence of Y278 has the highest sequence identity (87.0%)with that of Malvastrum yellow vein virus.So it is a distinct begomovirus,for which the name Malvastrum yellow vein Baoshan virus(MYVBSV)is proposed. Sequence comparison indicates that Y278 probably have arisen from recombination between Malvastrum yellow vein viru(MYVV)and viruses related with Sida leaf curl virus(SiLCV).Tomato yellow leaf curl China virus(TYLCCNV)DNA-A and associated DNAβmolecules were isolated from three Malvastrum coromandelianum samples in Yunnan. Y278 DNA-A and DNAβfrom Y277,Y278 and Y281 were sequenced.Comparisons with other begomoviruses showed that Y278 DNA-A is most closely related to TYLCCNV-[Y264]with 100%nucleotide sequence identity.The three associated DNAβshares the highest nucleotide sequence identity(97.0～99.7%)with TYLCCNV DNAβ.So Malvastrum coromandelianum is an alternative host of TYLCCNV.The DNA-A sequence of Y277 from M.coromandelianum sample collected in Baoshan,Yunnan were determined.Comparison of nucleotide sequences indicate that Y277 has the highest nucleotide sequence identity(99.6%)with that of MYNYNV. Infectious clone of DNA-A of Y277 was constructed.Y277 DNA-A alone or together with MYVYNV DNAβcould systemically infect Nicotiana benthamiana plants,so DNAβmolecule is not necessary for symptom induction of Y277 DNA-A,but DNAβcan intensify symptom severity and increase DNA-A accumulation in plants. Mixed infections were tested with specific primers among 22 Malvastrum coromandelianum samples collected from several areas of Yunnan province.The results showed that most samples were infected by no less than two kinds of begomoviruses and begomovirus/DNAβcomplex occur commonly in fields. MYVBSV and TYLCCNV were found in many Malvastrum coromandelianum samples collected from different areas of Yunnan province,indicating these viruses occur widely in fields.