First Report of Leek yellow stripe virus in Garlic in the State of Guanajuato, Mexico.

Garlic (Allium sativum L.) can be affected by a virus complex (1) consisting of two potyviruses, Onion yellow dwarf virus (OYDV) and Leek yellow stripe virus (LYSV), and two carlaviruses, Garlic common latent virus (GCLV) and Shallot latent virus (SLV) (1). To identify the components of the virus complex that could be present in garlic plants in Guanajuato State, which is the second largest garlic producer in the country and where presumptive viral symptoms were initially observed in December 2004, a survey was carried out in six locations: San Miguel de Allende and San Luis de la Paz in northern Guanajuato; Irapuato and Villagrán in the central region; and Salamanca and Valle de Santiago in the southern part of the state. Enzyme-linked immunosorbent assay (ELISA) was carried out to detect LYSV, OYDV, GCLV, and SLV in 195 garlic leaf samples collected during January 2005 from plants with leaf yellow stripe, mosaic, enation, deformation, or dwarfism symptoms. A set of primers, previously reported and specific to the coat protein cistron of LYSV (1), were synthesized and used in a reverse transcriptase-polymerase chain reaction (RT-PCR). The amplified product (1,020 nucleotides) was cloned into plasmid pGEM T-Easy (Promega, Madison, WI) and sequenced (Gen-bank Accession No. DQ841554). Sequence analysis showed that the cloned DNA fragment shared 97% similarity with the coat protein cistron of LYSV isolate no. 3 from Okinawa (GenBank Accession No. AB194632). The fragment was then radioactively labelled and used as a probe in the RNA blot analysis of all samples to confirm the ELISA results of LYSV. Of the 195 samples, 64 tested positive by RNA blot analysis. Forty-one of these were also positive by ELISA for LYSV. Preliminary, positive ELISA results were also obtained for OYDV, GCLV and SLV. To our knowledge, this is the first report of LYSV in the State of Guanajuato and in Mexico. The correct identification of viruses present in garlic will help to use the appropriate strategies to reduce viral incidence in this garlic-producing region. Reference: (1) T. V. M. Fajardo et al. Fitopatol. Bras. 26:619, 2001.

Coat protein sequence comparisons of three Medican isolates of papaya ringspot virus with other geographical isolates reveal a close relationship to American and Australian isolates.

The coat protein gene of the papaya ringspot virus was cloned and sequenced in three Mexican isolates (two from Veracruz, and one from Chiapas). The sequences of these viral isolates were compared to those of eleven isolates from other parts of the world. They had higher similarity to isolates from Australia and the United States than to Asian isolates. A region of about one hundred nucleotides neighboring the putative aphid transmission triplet of the coat protein, contained repeats of an EK (glutamic acid-lysine) motif in all the sequences. The bearing of this region on the genetic relationships and geographical distribution of the isolates is analyzed and discussed.