First Report of Shallot latent virus in Garlic in Argentina.

Because of exclusively agamic propagation, garlic is commonly infected with a virus complex mainly composed of species within the genera Potyvirus, Allexivirus, and Carlavirus. This virus complex causes leaf striping that ranges from various shades of green to yellow and results in yield losses (2,4). Onion yellow dwarf virus, Leek yellow stripe virus (potyviruses), Garlic virus A, Garlic virus C (allexiviruses), and Garlic common latent virus (carlavirus) have been detected in Argentina previously (1,2). Recently, Shallot latent virus (SLV; another carlavirus) was detected in 25 of 30 garlic plants (cv. Morado) growing in four different fields near Córdoba, Argentina by double-antibody sandwich (DAS)-ELISA using BIOREBA (Reinach, Switzerland) antibodies. To confirm the presence of the virus, DAS-ELISA-positive plants were also analyzed by one-step reverse transcription (RT)-PCR using the Access RT-PCR system (Promega, Madison, WI) with specific primers reported by Tsuneyoshi et al. (3). RNA extractions were performed from 100 mg of leaves with the Qiagen RNeasy Plant Mini Kit (Qiagen, Valencia, CA). Primers used were Car-V1 (5'-AAACCTTTTGGTTCACTTTAGG-3'); Car-V2 (5'-AGGTGCATTGTTATCATTACTGG-3'); and Car-Cp3 (5'-GCGTGCTATATTTAAGTTGCATAC-3'). Primer pairs Car-V1/Car-Cp3 and Car-V2/Car-Cp3 were used for the amplification of the coat protein (CP) gene of SLV and an isolate of SLV formerly known as Garlic latent virus, respectively. Fragments of 992 bp and 1,079 bp were amplified with these primer pairs, respectively. The RT-PCR products were cloned with the TOPO TA Cloning Kit in the 3.9-kb pCR-TOPO vector (Qiagen). The nucleotide sequences of both fragments were determined and were found to be identical (GenBank No. GU355922) showing 94.2% nt sequence identity with the CP gene of an isolate of SLV from Indonesian garlic (GenBank No. AB004686) formerly referred to as Garlic latent virus (3). Consequently, the Argentinean virus is now considered a garlic isolate of SLV. References: (1) E. Cafrune et al. Plant Dis. 90:898, 2006. (2) V. C. Conci. Virus y Fitoplasmas de Ajo. Page 267 in: 50 Temas Sobre Producción de Ajo. Vol. 3. J. L. Burba, ed. Ediciones INTA, Mendoza, Argentina. 1997. (3) T. Tsuneyoshi et al. Arch. Virol. 143:1093, 1998. (4) D. G. A. Walkey and D. N. Antill. J. Hortic. Sci. 64:53, 1989.

Effect of Two Allexivirus Isolates on Garlic Yield.

Garlic (Allium sativum) is infected by numerous viruses forming a viral-complex, which is widely distributed in the garlic production regions of Argentina. This work is the first report of the effect of two Allexivirus isolates, Garlic virus A (GarV-A) and Garlic virus C (GarV-C), on garlic yield. Garlic cvs. Morado-INTA and Blanco-IFFIVE were used in the experiments, and four treatments were evaluated: plants inoculated with GarV-A only, GarV-C only, virus-free plants (negative control), and plants infected with the virus-complex. Assays were performed in anti-aphid cages and in the field during 2002 and 2003. GarV-A caused significant reductions in bulb weight (14 to 32%) and diameter (6 to 11%) compared with the negative control in the two cultivars under both assay conditions. GarV-C caused less damage than GarV-A (15% in weight and 5% in diameter) with respect to the negative control in cv. Blanco-IFFIVE, and did not produce significant yield losses in cv. Morado-INTA in either year or under either assay condition.