Sweepoviruses Cause Disease in Sweet Potato and Related Ipomoea spp.: Fulfilling Koch's Postulates for a Divergent Group in the Genus Begomovirus

Abstract

Sweet potato (Ipomoea batatas) and related Ipomoea species are frequently infected by monopartite begomoviruses (genus Begomovirus, family Geminiviridae), known as sweepoviruses. Unlike other geminiviruses, the genomes of sweepoviruses have been recalcitrant to rendering infectious clones to date. Thus, Koch's postulates have not been fullfilled for any of the viruses in this group. Three novel species of sweepoviruses have recently been described in Spain: Sweet potato leaf curl Lanzarote virus (SPLCLaV), Sweet potato leaf curl Spain virus (SPLCSV) and Sweet potato leaf curl Canary virus (SPLCCaV). Here we describe the generation of the first infectious clone of an isolate (ES:MAL:BG30:06) of SPLCLaV. The clone consisted of a complete tandem dimeric viral genome in a binary vector. Successful infection by agroinoculation of several species of Ipomoea (including sweet potato) and Nicotiana benthamiana was confirmed by PCR, dot blot and Southern blot hybridization. Symptoms observed in infected plants consisted of leaf curl, yellowing, growth reduction and vein yellowing. Two varieties of sweet potato, ‘Beauregard’ and ‘Promesa’, were infected by agroinoculation, and symptoms of leaf curl and interveinal loss of purple colouration were observed, respectively. The virus present in agroinfected plants was readily transmitted by the whitefly Bemisia tabaci to I. setosa plants. The progeny virus population present in agroinfected I. setosa and sweet potato plants was isolated and identity to the original isolate was confirmed by sequencing. Therefore, Koch's postulates were fulfilled for the first time for a sweepovirus.

Small RNA deep sequencing‐based detection and further evidence of DNA viruses infecting sweetpotato plants in Tanzania

“…Sweepoviruses are generally wide spread (Paprotka et al ., ; Esterhuizen et al ., ) and in East Africa a distinct species has been reported from Uganda (Wasswa et al ., ).The severe stunting of plants and leaf curling observed in this study (Fig. ) indicate that these viruses may be inflicting significant damage on sweetpotato plants in Tanzania, which is supported by recent experimental findings (Trenado et al ., ). Thus, apart from SPVD, yield reduction caused by these viruses may be high and there is a need to pay attention to them if sweetpotato production is to be increased in East Africa.…”

“…In the past, most attention has been paid to the viruses of the SPVD complex from the families Potyviridae and Closteroviridae . The evidence provided in this work as well as elsewhere (Cuellar et al ., ; Trenado et al ., ; Wasswa et al ., Esterhuizen et al ., ) points to the importance of considering viruses from a much wider range of taxonomic groups during management procedures for the control of viruses and their associated diseases of sweetpotato plants in Africa. Yield reduction associated with sweepoviruses in East Africa remains poorly studied.…”

“…There are several other viruses of significance in sweetpotato production (Clark et al ., ). For instance, Koch's postulates were recently fulfilled for sweepoviruses, which infect sweetpotato and related species (Trenado et al ., ). Moreover, recent reports show the existence of viruses that infect sweetpotato plants without causing symptoms (Kreuze et al ., ; Cuellar et al ., ; Mbanzibwa et al ., ).…”

Exploring the Polyadenylated RNA Virome of Sweet Potato through High-Throughput Sequencing

“…During the last decades, over 30 sweet potato viruses were detected in the world [3], [13], and 11 of these have been reported in China [14]. SPFMV, SPLV and SPCFV are considered as the major viruses in China [4], [14].…”

Characterization of Non-coding DNA Satellites Associated with Sweepoviruses (Genus Begomovirus, Geminiviridae) – Definition of a Distinct Class of Begomovirus-Associated Satellites

“…DIG-dUTP was incorporated by using the PCR DIG Probe Synthesis System Kit (Roche Diagnostics) according to the manufacturer’s instructions. As a size control, Southern blot analysis was also carried out with the same sample using a probe corresponding to the coat protein gene of SPLCV, isolate BG30 ( Trenado et al, 2011 ). For this, DNA was analyzed both undigested and digested with a restriction enzyme which recognizes a unique site in the satellite ( Pst I) and SPLCV ( Bam HI).…”