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Title: First report of a bigomovirus infecting sweetpotato in Kenya

item D.W., MIANO
item C.A., CLARK
item D.R., LABONTE
item M.W., HOY
item Hurtt, Suzanne
item Li, Ruhui

Submitted to: Meeting Abstract
Publication Type: Research Notes
Publication Acceptance Date: 3/29/2006
Publication Date: 6/1/2006
Citation: Miano, D. W., LaBonte, D. R., Clark, C. A., Valverde, R. A., Hoy, M. W., Hurtt, S. Li, R. 2006. First Report of a Begomovirus Infecting Sweetpotato in Kenya. Plant Disease. 90:832.

Interpretive Summary:

Technical Abstract: sence ofbegomoviruses, such as Sweet potato leaf curl virus (SPLCV), which have recently been found in the Americas and Asia. Sweetpotato plants with symptoms including curling at the leaf margins, similar to those observed in SPLCV -infected sweetpotato plants (1), were collected from a germplasm collection plot at Kakamega Research Station in Western Kenya in February 2005. Whiteflies, the vectors for begomoviruses, were also observed in the same plots. Ipomoea setosa plants graft¬inoculated with scions from infected sweetpotato developed symptoms of leaf curling, leaf rolling, interveinal chlorosis and stunting, similar to those caused by infection with SPLCV alone or with Sweet potato feathery mottle virus. Total DNA was isolated from 100 mg ofleaves obtained from ten 1 setosa plants graft-inoculated with infected sweetpotato clones using the GenEluteTM plant Genomic DNA Kit (Sigma-Aldrich Inc., St. Louis, MO). Sweetpotato cuttings from 39 clones, selected from the Kenyan germplasm collection for their resistance or susceptibility to sweetpotato virus disease (SPVD), were sent to the Plant Germplasm Quarantine Office ofUSDA-ARS. The cuttings were planted in a greenhouse, and total DNA was extracted directly from sweetpotato leaves one month later using a CT AB extraction method (2). Degenerate primers SPGlISPG2 developed for PCR detection ofbegomoviruses (2) amplified a 912 bp DNA fragment from three out often DNA extracts from 1 setosa, and five out of39 sweetpotato samples. The degenerate primers anneal to regions of open reading frame (ORF) AC2 and ORF ACI which are highly conserved in begomoviruses infecting sweetpotato. SPLCV-specific primers PW285-1/PW285-2 (1) amplified a512 bp DNA fragment ofORF ACI from seven samples. None of the collections from Kenya were positive in real time PCR using primers specific to SPLCV -US (3), that anneal to regions ofORF ACI and ORF AC4, strongly suggesting that the begomoviruses found in Kenya are different from the US strain. The 512 bp bands amplified using specific primers PW285-1/PW285-2 were excised from agarose gels and purified using MinEluteTM Gel Extraction kit (QIAGEN Inc., Valencia, CA) and ligated into pGEM- T Easy vector (Promega Corp., Madison, WI). Recombinant plasmids were transformed into JM 109 Escherichia coli cells. Nucleotide sequences were determined by automated sequence analysis, and a 457 nt fragment from ORF AC 1 used for comparisons. Sequences were closely related to SPLCV (GenBank accession no. AF104036) with nucleo.tide sequence identities that vary from 93% to 97%. Yellow vein mottle symptoms, similar to those observed in Ipomoea aquatica infected with SPLCV (I) were also observed in sweetpotato plants in Western Kenya, though DNA was not extracted from these plants. More work is needed to determine if these symptoms are also caused by begomoviruses. The presence of the virus poses a challenge to the dissemination of planting materials in the region especially because begomovirus-infected plants often do not show symptoms. To our knowledge, this is the first report of a begomovirus infecting sweetpotato in Kenya, and in the East African region.