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First Report of Leek yellow stripe virus in Garlic in Ohio

Leek yellow stripe virus (LYSV), genus Potyvirus, family Potyviridae, infects a wide range of Allium species worldwide. LYSV is one of several viruses that chronically infect garlic, Allium sativum L. The garlic virus complex, which includes LYSV, Onion yellow dwarf virus, and Garlic common latent virus, is perpetuated by asexual propagation (4) and is transmitted to clean planting material by aphids (3). This virus complex can reduce garlic bulb weight by nearly three quarters (2), and LYSV-only infections can result in approximately a one-quarter reduction in bulb weight (2). Garlic is grown as a small-scale, specialty crop in Ohio. During late May and early June 2013, garlic plants with virus-like symptoms were collected from Medina, Holmes, and Wayne counties, Ohio. Plants exhibited chlorotic streaking, foliar dieback, dwarfing, small bulbs, and cylindrical bulbs that failed to differentiate into cloves. Incidence of affected plants in the fields was up to 5% and all fields had early season aphid infestations. Flexuous rods were observed in TEM micrographs of plant sap from symptomatic leaves. Five symptomatic plants and six asymptomatic plants (from fields with symptomatic plants) were evaluated for LYSV by DAS-ELISA (Agdia, Inc., Elkhart, IN). Reverse transcriptase (RT)-PCR with LYSV-specific primers LYSV-WA and LYSV-WAR (3) was performed with cDNA generated by the High Capacity cDNA Reverse Transcription Kit (Applied Biosystems, Foster City, CA). Both foliar and bulb tissues were tested using both detection methods. Forty percent of symptomatic plants and 67% of asymptomatic plants tested positive for LYSV with both ELISA and RT-PCR. LYSV was detected in both foliar and bulb tissues, including both tissues from asymptomatic plants. Five PCR amplicons generated from both foliar and bulb tissue were sequenced and shown to share 96 to 98% maximum identity with an LYSV polyprotein gene accession in GenBank (AY842136). This provided additional support that the detected virus was LYSV. LYSV was initially difficult to detect in Ohio fields due to low disease incidence and subtle symptom development. Use of virus-tested garlic bulbs can improve yield for several years, even following viral reinfection by aphids, compared to growing garlic from chronically infected bulbs (1). However, many growers routinely save bulbs from year to year and lack access to or knowledge of virus-tested sources of garlic bulbs. Conducive conditions, chronic infections, or co-infections with other viruses enhance the severity of symptoms and yield loss (2). LYSV has previously been reported in garlic producing regions of the northwestern United States (3), and to our knowledge, this is the first report of LYSV in garlic in Ohio.

References: (1) V. Conci et al. Plant Dis. 87:1411, 2003. (2) P. Lunello et al. Plant Dis. 91:153, 2008. (3) H. Pappu et al. Plant Health Progress 10, 2008. (4) L. Parrano et al. Phytopathol. Mediterr. 51:549, 2012.