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First Report of Potato virus Y in Kalimeris indica in China

Kalimeris indica, a tall, fecund plant in the family Asteraceae, a native of China, Japan, and Siberia, has been around a long time. It was first mentioned in 1825 and is popular in Europe. It is widely grown in Heilongjiang, Liaoning, Jilin, Hebei, Shanxi, and other provinces in China for its medicinal properties. K. indica is believed to have a clearing effect on eyesight, reduces blood pressure and swelling, and is rich in carotene, which can reduce internal heat, enhancing human immunity. It also grows as a weed around tobacco fields and can transmit viruses to tobacco. In June of 2012, we observed diffuse chlorotic and necrotic spots on the leaves of K. indica in the field in Liaoning Province. Sap extracts from symptomatic plants were tested by direct antigen coated ELISA using polyclonal antibodies specific to Potato virus Y (PVY), Cucumber mosaic virus (CMV), and Tobacco mosaic virus (TMV). Samples were negative for CMV and TMV but positive for PVY. RNA extracted from symptomatic leaves of K. indica was used as template for obtaining PVY genomic sequences. cDNA of the PVY genome were prepared using PrimeScript II High Fidelity RT-PCR Kit (TaKaRa Biotechnology Dalian Co., Ltd) as described by the manufacturer. The strategy for amplification of overlapping genome fragments and determining the 5′-terminal end of the genome by 5′-RACE and 3′-terminal end of the genome by 3′-RACE was described previously (1). PCR amplification was performed using the TaKaRa PrimeSTAR GXL DNA Polymerase (TaKaRa Biotechnology Dalian Co., Ltd) following the manufacturer's instructions with PVY1F(5′-AAAACAACTCAATACAACAT-3′), PVY3R(5′-GTCTCCTGATTGAAGTTTACAGYCACT-3′), R2743 (5′-CTGTTGCTGCCGTGTCAATTAT-3′), F1810 (5′-CTGGCTGAGTTTAGGCGGAAGA-3′), R5868 (5′-GCTTGACTTGCCCATACCAACA-3′), F5711 (5′-CTCACCAGGGCAAGAACAAATC-3′), F830 (5′-ATCTCGCCAGGACGGACAAGTG-3′), R2678 (5′-GCTAAGGCGGACAATAACGATG-3′), R7713 (5′-TTCAGGTAGACGCCGAAGCAAT-3′), F7442 (5′-TTACTGAGGCGGATAAAGAGGA-3′), R8940 (5′-TCCGTTGATGTTTGGCGAGGTT-3′), F1 (5′-AATGAAAATGCCCAAGAGTAAG-3′), F3 (5′-TCTGCGCGATGGAAGTTTGG-3′), R1 (5′-TCTGGGCATCAGTCTTGTATCG-3′), R2 (5′-AACTTCTCGTTTCCCCGCAACT-3′) primers. The expected genome sequence was amplified from symptomatic leaves and the amplicon was cloned and sequenced (GenBank Accession No. JQ971975). The complete genome sequence named ME162 was determined to be 9,714 nucleotides in length, excluding the 3′-terminal poly (A) tail. Comparisons of amplicon with the nucleotide sequences available in the NCBI database using BLAST showed 99% identity with PVY from Uganda (GenBank Accession No. DQ157180). The isolate was most closely related to potato virus Y N strain. The serological and sequence data revealed that K. indica plants were infected by PVY. To our knowledge, this is the first report of PVY in K. indica in China. K. indica is an important medicinal plant. This report provides the scientific evidence for virus control on future K. indica plantings. K. indica grows as a weed around tobacco fields and can serve as an indirect host for virus transfer. Controlling virus incidence on K. indica is an important way to protect tobacco from infection by PVY.

Reference: (1) J. Chen and J. P. Chen. Chin. J. Virol. 18:371, 2002.