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First Report of Fig mosaic virus Infecting Common Fig (Ficus carica) in China

The common fig (Ficus carica) is one of the earliest plants domesticated by humans. It has been cultivated in China ever since the early seventh century. Fig fruit is an important traditional Chinese medicine and a fine health food, featuring a unique flavor and rich nutrients. In addition to its great medicinal values, its abundant availability in the Xinjiang province of China has made the fig one of the most popular fruits in the country. One of the major diseases that affect figs is the fig mosaic disease (FMD) (1,4), which was reported in China in 1935 (3). A causal agent of this disease is associated with the Fig mosaic virus (FMV), a negative-strand RNA virus with six RNA segments (2). In 2013, and later during a survey in 2014, fig plants in several orchards in Xinjiang displayed symptoms of a virus-like disease, which was characterized as FMD. These symptoms included chlorotic clearing as well as banding of leaf veins along with various patterns of discoloration, severely distorted leaves, and deformed fruits. Total RNA extracts (TRIzol reagent, Ambion) from 18 symptomatic and four asymptomatic leaf samples were subjected to reverse reaction (RT) assays using M-MLV reverse transcriptase (Promega, Fitchburg, WI) with primer FMV-GP-R (TATTACCTGGATCAACGCAG). PCR analysis of the synthesized cDNA was performed using FMV-specific primers FMV-GP-F (ACTTGCAAAGGCAGATGATA) and FMV-GP-R. Amplicons of 706 bp produced by RT-PCR assays were obtained from most (15 out of 18) of the symptomatic samples; however, none was obtained from the four asymptomatic leaves. The purified amplicons were cloned and sequenced. BLAST analysis of these sequences revealed more than 94% nucleotide identity with glycoprotein precursor (GP) genes of an FMV-Serbia isolate (SB1). One sequence was deposited in NCBI databases, and one sequence was submitted to GenBank (Accession No. KM034915). RNA segments 2 to 6 of FMV were also amplified by RT-PCR and sequenced. These sequences showed 94 to 96% identity with FMV sequences deposited in the NCBI databases. The collected samples were further detected by Northern-blot hybridization with a digoxigenin-labeled RNA probe, which targets the RNA1 genome of the FMV. The result was in line with RT-PCR detection. To our knowledge, this is the first report of FMV in fig trees in China. Considering the economic importance of fig plants and the noxious nature of FMV, this virus poses a great threat to the economy of the fig industry of Xinjiang. Thus, it is important to develop immediate effective quarantine and management of this virus to reduce any further predictable loss.

References: (1) T. Elbeaino et al. J. Gen. Virol. 90:1281, 2009. (2) K. Ishikawa et al. J. Gen. Virol. 93:1612, 2012. (3) H. A. Pittman. J. West Aust. Dept. Agric. 12:196, 1935. (4) J. J. Walia et al. Plant Dis. 93:4, 2009.