First Report of Peanut Mottle Virus Infecting Peanut in Northeast China

Peanut (Arachis hypogaea L.) is an important food, oil, and forage crop widely grown in China. Peanut mottling disease is mainly caused by peanut mottle virus (PeMoV), which belongs to the genus Potyvirus, family Potyviridae. PeMoV infection causes mild mottle to mosaic patterns, chlorosis, and stunting symptoms on peanut (Soumya et al. 2014), and it results in considerable losses in peanut-planting regions worldwide (Spiegel et al. 2008). In July 2017, 20 peanut leaf samples with mosaic, mottle, and chlorotic symptoms were collected from the urban area of Shenyang, Liaoning province, northeast China, where at least 10% of more than 8,000 peanut plants in this region exhibited visual symptoms. Total RNA extracted from symptomatic peanut leaves was analyzed by small RNA next-generation sequencing using an Illumina Genome Analyzer (Biomarker Bio, Beijing, China). The raw data reads were filtered for quality and de novo assembled into larger contigs using Velvet Software 1.2.08 (Zerbino et al. 2008). The assembled contigs based on the sequences of virus-derived small interfering RNAs were searched against NCBI nucleotide databases using BLASTn, of which 56 contigs showed high homologies to the genomic sequence of PeMoV. To confirm the PeMoV infection, crude extracts of symptomatic leaves were mechanically inoculated onto 20 leaves of 10 peanut plants. Typical yellowing mottle and malformation symptoms were observed on upper, noninoculated leaves of nine peanut plants at 15 days postinoculation (dpi). Total RNA extracted from original samples and inoculated plants was analyzed by reverse transcription polymerase chain reaction (RT-PCR) at 15 dpi using six pairs of PeMoV-specific primers (data not shown). The overlapping PCR products with sizes of 2,087, 1,984, 972, 1,872, 1,639, and 1,554 bp were cloned into pEASY-T1 vector (Transgen, Beijing, China), and at least three clones of each PCR product were analyzed by DNA sequencing, respectively. The complete nucleotide sequences of PeMoV Liaoning isolate were assembled and submitted to NCBI under the GenBank accession number MH270528. Nucleotide BLAST analysis using the complete genome sequence of PeMoV Liaoning isolate indicated that the isolate was most close to PeMoV Korean isolate (KF977830, identity 99.4%) and to Colombia isolate (KU708532, identity 96.1%). To our knowledge, this is the first report on the occurrence and sequences of PeMoV infecting peanut in northeast China. PeMoV can be transmitted through infected seeds and aphids, which pose a serious threat to the cultivation of peanut. The finding reported here will assist further investigations on the epidemiological forecast and management of the PeMoV in China.