First Report of Maize Yellow Mosaic Virus on Zea mays in South Korea.

Abstract

Maize yellow mosaic virus (MaYMV) is a novel putative polerovirus recently found in maize (Zea mays) in China and has been detected not only in Asia but also in Africa and South America (Chen et al. 2016; Goncalves et al. 2017; Palanga et al. 2017). In addition, MaYMV infection has also been reported in sugarcane (Saccharum spp.) and itch grass (Rottboellia cochinchinensis) (Yahaya et al. 2017). Recently, the first occurrence of MaYMV in South Korea has been reported from Panicum miliaceum and Sorghum bicolor using high-throughput RNA sequencing (Lim et al. 2018). Therefore, to confirm whether MaYMV exists in maize in South Korea, a total of 26 maize samples with yellowing, yellow stripe, and chlorosis symptoms were collected from three provinces (Chungcheongbuk-do, Gangwon-do, and Gyeongsangnam-do) in August and September 2017. Total RNA was extracted from all samples using the easy-spin Total RNA Extraction Kit (iNtRON Biotechnology, Seongnam, Korea). Reverse transcription polymerase chain reaction (RT-PCR) was conducted using SuPrimeScript RT-PCR Premix (GeNet Bio, Daejeon, Korea) and MaYMV-specific primers (Chen et al. 2016), producing an amplicon with expected size of 753 bp, using protocols described previously (Lim et al. 2018). Five out of six samples collected from Chungcheongbuk-do, five out of 10 samples collected from Gangwon-do, and one out of 10 samples collected from Gyeongsangnam-do were confirmed to be infected with MaYMV. One RT-PCR fragment of MaYMV from each region (Gangwon-do, Chungcheongbuk-do, and Gyeongsangnam-do) was directly sequenced (Macrogen, Daejeon, Korea), and the sequences were deposited in GenBank under accession numbers MG020517, MG020518, and MG020519, respectively. The partial nucleotide sequences of MaYMV determined in each sample collected from Chungcheongbuk-do and Gyeongsangnam-do were identical, and these nucleotide sequences differed by one nucleotide from that identified in the sample collected from Gangwon-do. The NCBI BLAST search showed that the three MaYMV isolates shared high nucleotide sequence homology (99 to 100%) with isolates Yunnan3 (KU291099) and Yunnan4 (KU291100) from maize in China. The MaYMV-infected samples showed yellow stripe and chlorosis symptoms, which tend to first appear on the tip and edge of the leaves and become worse. However, further studies are needed, because it is uncertain whether the symptoms were caused by a single infection with MaYMV. To the best of our knowledge, this is the first report of MaYMV on Z. mays in South Korea.