First Report of Bean yellow mosaic virus in Vanilla in Hawaii

Vanilla plants are grown to produce one of the most widely used flavors in the world. Vanilla planifolia (Orchidaceae) was introduced into Hawaii from Mexico, Tahiti, Samoa, and Fiji. Vanilla is one of the components of diversified agriculture in Hawaii. Bean yellow mosaic virus (BYMV) is a member of the genus Potyvirus in the family Potyviridae (Parrella and Lanave 2009). In 2011, Bhadramurthy first reported that vanilla plants showing severe yellow mosaic and leaf distortion symptoms were infected by BYMV in India (Bhadramurthy et al. 2011). Recently, we have found this virus infecting vanilla in Hawaii. In December 2016, we observed vanilla plants exhibiting severe chlorotic mosaic symptoms in the Foster Botanical Garden in Honolulu, HI (21°19′11.61″ N, 157°51′24.19″ W). Symptomatic leaves from two vanilla plants were collected and verified to be potyvirus-positive by ELISA using potyvirus-specific antibodies (Agdia, Elkhart, IN). Interestingly, although Dasheen mosaic virus (DsMV) has been reported from vanilla (Puli’uvea et al. 2017), all these plants tested negative for DsMV by ELISA. We then conducted reverse transcription (RT)-PCR using a universal primer pair to amplify the partial nuclear inclusion B (NIb) gene of the potyviral genome: NIb2F (5′-GTITGYGTIGAYGAYTTYAAYAA-3′) and NIb3R (5′-TCIACIACIGTIGAIGGYTGNCC-3′) (Zheng et al. 2010). The expected 350-bp product was amplified and cloned into the pGEM-T Easy vector (Promega, Madison, WI). Ten positive clones were randomly selected and sequenced using T7 and SP6 primers by Sanger sequencing at the University of Hawaii’s Advanced Sequence Genomics Proteomics and Bioinformatics laboratory. All of the sequences were essentially identical to one another (accession no. KY440223) and shared 89.0% nucleotide sequence identity and 99.6% amino acid sequence identity to BYMV (JF707769.1). One additional BYMV-specific primer set, BYMV-CP-5 (5′-GAACTGTTGGAACGTTTTCAATTCC-3′) and BYMV-CP-3 (5′-TCTGTTCCAACATTGCCATCAAG-3′) designed to amplify a fragment of the coat protein (CP) region to confirm the virus identity. The expected product (KY475574) showed 93.0% nucleotide sequence identity and 100% amino acid sequence identity with published BYMV sequences (EU082119.1). We then tested six V. planifolia leaf samples with symptoms of yellow mosaic and leaf distortion for BYMV infection using BYMV-specific ELISA (DSMZ, Brausschweig, Germany). All six symptomatic samples tested positive, while six nonsymptomatic V. planifolia leaf samples tested negative in this test. To our knowledge, this is the first report of BYMV infecting vanilla in the U.S.A. BYMV is an aphid-transmitted nonpersistent potyvirus that has a wide host range (Radwan et al. 2008). Attention should be paid to limit the spread of the virus and to avoid possible serious damage to the developing vanilla industry in Hawaii. © 2017, American Phytopathological Society. All rights reserved.