The Detection And Identification Of Begomoviruses Isolated From Malvastrum Coromandelianum In Panzhihua,Sichuan Province

Whitefly-transmitted geminiviruses (WTG), known as one of the most important pathogen for most economic crops, have caused great damage and losses to crop production around the world. In recent years, many provinces and regions in China, such as Hainan, Guangdong, Fujian, Yunnan, etc., have many yield loss reports about WTGs. In this research, Malvastrum coromandelianum samples showing yellow vein symptoms were collected from fields in Panzhihua, Sichuan province. Weeds such as Malvastrum coromandelianum, are considered to be the intermediate hosts (between insects and crops) and initial sources of infection. Molecular detections, as well as viral genome structure, mutation and evolution analysis were conducted to identify begomoviruses in these samples.Degenerate primers PA/PB were used to detect begomovirus via PCR. PCR results showed that 108 samples (64 were from Renhe region and 44 from Hongge town) were positive (positive ratio was 69.68%) among all 155 samples and 500bp specific DNA segments were amplified from them. Full length DNA-A components of two geminiviruses, Tomato yellow leaf curl China virus (TYLCCNV) and Malvastrum yellow vein Yunnan virus (MYVYNV) were also obtained by PCR. Aligning and phylogenetic trees revealed that all eight full length DNA-As sequences, obtained from sample No.SC44, SC95, SC170, SC211, SC314, SC344, SC327 and SC329, showed the maximal nucleotide identity of 98.4%-99.9% with MYVYNV (Accession No. AJ971501.2). TYLCCNV-SC44 yielded from sample SC44 showed the maximal 99.1% nucleotide identity with that of TYLCCNV-TbY10 (Accession No. AJ319675), while TYLCCNV-SC327 showed 99.5% nucleotide identity with TbSC101 (Accession No. JN082233.1). Degenerate primerβ01/β02 were also used to detect satellite DNAβ. PCR results showed that the 1300bp specific DNA segments were detected in 89 samples (4 were from Renhe region and the other 34 from Hongge town) and positive ratio came to be 57.42%. Two kinds of satellites, MYVYNB associated with MYVYNV and MYVB associated with MYVV, were identified in these 89 samples. Neither DNAa nor DNA-B component was found in all samples.Co-infection detection was also deployed with special primers for DNA-A and DNAβof MYVYNV, TYLCCNV and MYVV. The results revealed that 70 samples, which took up a rate of 45.16% in all 155 samples, were found to be co-infected by MYVYVN and TYLCCNV. This showed that co-infection of begomoviruses was often occurred in nature. Nineteen samples were found to be infected both with MYVYNV and TYLCCNV, in addition with MYVYNB and MYVB, which took up a rate of 12.26%. Only one sample was found to be co-infected with MYVYNB, MYVB and MYVYNV, However, No sample was found to be co-infected with MYVYNB, MYVB and TYLCCNV.