First report of shallot virus X in Garlic in Ecuador

Abstract:

Garlic (Allium sativum L.) is widely cultivated in the Andean region of Ecuador. Viral diseases of garlic are widespread and losses in crop yields due to virus infection are a serious problem because they are propagated vegetatively (Kamenetsky and Rabinowitch 2001). Shallot virus X (ShVX) is a known pathogen of species belonging to the genus Allium. ShVX was first detected in shallot in Russia (Kanyuka et al. 1992). Thirty garlic leaf samples from both symptomless (10) and symptomatic (20) plants (showing chlorotic streaking and leaf curling) were collected during July 2015 from Alausí (Chimborazo Province) across multiple fields. Seventeen out of 30 garlic samples tested by double antibody sandwich ELISA using antibodies for ShVX (DSMZ AS-1042) showed a positive reaction and 13 of the ELISA-positive samples showed symptoms of the disease. Total RNA was extracted from 100 mg of 10 infected plant leaves using a modified Trizol (Invitrogen, U.S.A.) protocol and analyzed by RT-PCR for ShVX using the degenerate primers 5′-CYGCTAAGCTATATGCTGAARGG-3′ and 5′-TGTTRCAARGTAAGTTTAGYAATATCAACA-3′ designed by Dovas et al. (2001). An expected amplicon of ∼200 bp was obtained. RT-PCR was then carried out using specific primers previously designed to amplify a ∼910-bp fragment of ShVX including the coat protein gene (ShVX-CPF: 5′-ATTTAGGGGTGAAGGTCTGT-3′; ShVX-CPR: 5′-GAGTTTTGAGGTCGTTGG-3′) (Perez-Egusquiza et al. 2008). These primers amplified fragments of the expected sizes. One positive amplicon was directly sequenced from PCR products (KY012791). The Ecuadorian ShVX isolate showed 94% nucleotide sequence identity with Russian ShVX isolate (JX310755.1) from shallot and 92 to 94% with a New Zealand ShVX isolates (EU835197.1, EU835196.1) from shallot. Other viruses were not tested in these experiments. On the basis of the ShVX specific RT-PCR, and ELISA, the presence of ShVX in Ecuador was confirmed. The study also suggests the presence of dry bulb mites (Aceria tulipae) in the region, its only known vector. The high rate of ShVX vegetative transmission and its known association with garlic and disease on other Allium species means that further studies are necessary to clarify the pathogenic potential of the virus and to confirm its distribution in other Allium crops across Ecuador. To our knowledge, this is the first report of ShVX infecting garlic in Ecuador.

Año de publicación:

2017

Keywords:

Fuente:

scopus