Bemisia tabaci (Genn.), the whitefly species that transmits begomoviruses, has been found throughout the globe. These infections affect various crops, medicinal plants, ornamental plants and weeds, resulting in significant losses every year (Silva et al. 2012). Begomovirus infections have been found in a broad variety of hosts, with weeds and ornamental plants providing reservoirs for begomoviruses, acting as “mixing bowls” for recombination events (Silva et al. 2012). Begomoviruses have also been reported in medicinal plants, such as ashwagandha (Withania somnifera) (Baghel et al. 2012).
Due to exclusive transmission by the whiteflies, each begomovirus has been isolated from various hosts and each host serves as a reservoir for many begomoviruses, clarifying a bilateral transmission phenomenon. Indeed, okra has been reported as a natural reservoir for BYVMV, OELCuV, OLCV, OMoV, OYCrV, OYVMV, and an alternative host for CLCuAlV, CLCuBaV, CLCuGeV, CLCuMuV, ToLCNDV, ToLCGV, and SiMMV (Shih et al. 2009). The high incidence of cotton-infecting begomoviruses in okra suggests that plants from the same Malvaceae family may be susceptible to infection, explaining why many regions in the Indian subcontinent have hedges or barriers around cotton farms to protect against begomovirus transmission.
The fact that begomovirus-associated satellites are capable to promiscuity replication is an intriguing feature of these viruses. Alpha- and betasatellites may interact with a variety of helper begomoviruses (Zhou 2013). Although a helper begomovirus is required for replication, betasatellites can be transreplicated by diverse non-cognate helper begomoviruses, including both monopartite and bipartite forms (Mansoor et al. 2006). For example, experimental data indicated that betasatellite DNA can be transreplicated by beet curly top virus (BCTV), a curtovirus (family Geminiviridae) that is not known to generally correlate with DNA satellites, with betasatellites complementing the host defense suppression mechanisms of this non-cognate helper virus (Patil and Fauquet 2010). Despite the observed replicative promiscuity, phylogenetic analysis indicates that betasatellites can be grouped according to the host from which they were originally isolated, suggesting that adaptation of betasatellites to their cognate helper begomoviruses for replication results from coevolution (Briddon et al. 2003).
Alphasatellites may be relatively mobile since they do not seem to have a preference for certain helper begomoviruses (Briddon et al. 2004). The widespread transmission of these molecules in hosts may be facilitated by OW bipartite begomoviruses which are not usually correlated with alphasatellites (Briddon et al. 2004). For a long time, scientists believed that DNA satellites could only be found in the OW. Satellite DNA related to begomovirus has expanded in recent years, as several alphasatellites have been attributed to new-world begomoviruses (Paprotka et al. 2010). The BCTV leafhopper vector was able to transmit ageratum yellow vein virus-associated alphasatellite DNA in laboratory studies, suggesting that alphasatellite DNA had been trans-encapsidated (Saunders et al. 2002).
CroYVB and CLCuMuA, DNA satellites of the monopartite begomovirus BYVMV, were found to infect okra according to the results. Natural monopartite begomovirus–betasatellite complexes infect dicots in the OW, but an alphasatellite–begomovirus complex has not been previously reported to infect okra in this region. The presence of an alphasatellite with the begomovirus–betasatellite complex identified in the current study may be due to vector transmission.