First Report of a Begomovirus Infecting Sweetpotato in Kenya

Abstract

Previous surveys for viruses in sweetpotatoes (Ipomoea batatas) in Africa did not assay for the presence of begomoviruses such as Sweet potato leaf curl virus (SPLCV), which have been found recently in the Americas and Asia. Symptomatic sweetpotato plants, including some with leaf curling symptoms similar to those observed in SPLCV-infected sweet-potato plants (2), were collected from a germplasm collection plot at Kakamega Research Station in Western Kenya during February 2005. Whiteflies, the vectors for begomoviruses, were observed in the same plots. Ipomoea setosa plants graft-inoculated with scions from the symptomatic sweetpotato developed leaf curl, leaf roll, interveinal chlorosis, and stunting symptoms similar to those caused by infection with SPLCV alone or in combination with Sweet potato feathery mottle virus. Total DNA was isolated from 10 I. setosa plants using the GenElute 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 of USDA-ARS. The cuttings were planted in a greenhouse. Total DNA was extracted from sweetpotato leaves 1 month later using a cetyltrimethylammoniumbromide (CTAB) extraction method (1). Degenerate primers SPG1/SPG2, developed for PCR detection of begomoviruses (1), amplified a 912-bp DNA fragment from 3 of 10 DNA extracts from I. setosa and 5 of 39 sweetpotato plants held in quarantine. The primers anneal to regions of open reading frame (ORF) AC2 and ORF AC1 that are highly conserved in begomoviruses infecting sweetpotato. SPLCV-specific primers PW285-1/PW285-2 (2) amplified a 512-bp DNA fragment of ORF AC1 from seven samples (two from I. setosa and five from I. batatas). Amplicons from three independent PCR assays of two samples and single PCR assays of four additional samples were cloned into the pGEM-T Easy vector. Clone inserts were sequenced, and compared with sequences deposited in GenBank using the basic local alignment search tool (BLAST). Sequences were closely related to SPLCV (GenBank Accession No. AF104036) with nucleotide sequence identities varying from 93% (GenBank Accession No. DQ361004) to 97% (GenBank Accession No. DQ361005). The presence of the virus poses a challenge to the dissemination of planting materials in the region because begomovirus-infected plants often do not show symptoms. To our knowledge, this is the first report of a begomovirus infecting sweetpotato in Kenya or the East African Region. References: (1) R. Li et al. Plant Dis. 88:1347, 2004. (2) P. Lotrakul et al. Plant Dis. 82:1253, 1998.

Occurrence and genetic variability of partial coat protein gene of Sweet potato leaf curl virus (SPLCV) in Kenya

“…Among the regions, Western Kenya had the highest risk of SPLCV followed by Coast region and Central region with the lowest. The results obtained in this study reported the presence of SPLCV in Western Kenya, in agreement with previous studies that SPLCV was present in the region and they are (Miano et al, 2006). The presence and high incidence of the virus in the Coast region was not expected.…”

“…Several of these viruses occur in East Africa, including SPFMV, (genus Potyvirus), Sweet potato mild mottle virus (SPMMV, genus Ipomovirus). Others includes those in the family Closteroviridae which, includes SPCSV (genus Crinivirus), Sweet potato chlorotic fleck virus (SPCFV, genus Carlavirus) and Sweet potato leaf curl virus (SPLCV, genus begomovirus) (Ateka et al, 2004;Miano et al, 2006;Wasswa et al, 2011). SPLCV is transmitted by Bemisia tabaci or through vegetative propagation.…”

“…SPLCV occurs worldwide (Briddon et al, et al 2006;Lotrakul et al, 1998). In Kenya, the virus was first reported in the Western region in a germplasm collection plot (Miano et al, 2006), but since then, no further work has been done to determine its overall distribution in the country. The aim of this study was to determine the distribution of the virus in the country and its genetic variability.…”

Novel begomovirus species of recombinant nature in sweet potato (Ipomoea batatas) and Ipomoea indica: taxonomic and phylogenetic implications

“…These are: sweet potato leaf curl virus (SPLCV) (Lotrakul et al, 1998;Lotrakul & Valverde., 1999), Ipomoea yellow vein virus (IYVV) (Banks et al, 1999) and sweet potato leaf curl Georgia virus (SPLCGV) (Lotrakul et al, 2003). SPLCV or related begomoviruses have been isolated from sweet potato in the Americas (Lotrakul et al, 2003;Fuentes & Salazar, 2003), Asia (Onuki & Hanada, 1998;Luan et al, 2006) and Africa (Miano et al, 2006) and from I. indica in Europe . Begomoviruses are likely to be present in many regions where sweet potato is grown but their prevalence and distribution is still unknown.…”

Molecular characterization of sweet potato leaf curl virus (SPLCV) isolates from Korea: phylogenetic relationship and recombination analysis

“…Begomoviruses infect Ipomoea plant species worldwide and have been identified in Japan, Israel, Peru, Italy, Spain, China, Taiwan, Korea, Kenya, and USA (Chung et al, 1985;Osaki and Inouye, 1991;Banks et al, 1999;Lotrakul et al, 2003;Fuentes and Salazar, 2003;Briddon et al, 2006;Miano et al, 2006;Simmons et al, 2009). Several begomovirus species (SPLCV, IYVV, SPLCGV, SPLCCaV, SPLCLaV, SPLCESV, SPGVaV, and SPMaV) have been reported to infect Ipomoea species and their genomes have been fully sequenced (Lotrakul et al, 1998;Banks et al, 1999;Lotrakul et al, 2003;Lozano et al, 2009;Paprotka et al, 2010).…”