A Bipartite Begomovirus Infecting Boerhavia erecta (Family Nyctaginaceae) in the Dominican Republic Represents a Distinct Phylogenetic Lineage and has a High Degree of Host Specificity

Abstract

Boerhavia erecta plants in and around agricultural fields in the Azua Valley of the southeastern Dominican Republic often show striking golden mosaic symptoms. Leaf samples from B. erecta plants showing these symptoms were collected in 2012 and 2013, and PCR tests with degenerate primers revealed begomovirus DNA-A and DNA-B components. The complete sequences of the DNA-A and DNA-B components of four isolates show a high degree of sequence identity (>96%) and a genome organization typical of New World (NW) bipartite begomoviruses. Sequence comparisons and phylogenetic analyses revealed that these isolates composed a new phylogenetic lineage of NW bipartite begomoviruses. The most closely related begomovirus is Merremia mosaic virus, a weed-infecting species from Puerto Rico. Because DNA-A sequence identities are well below the 91% threshold, these isolates represent a new begomovirus species, for which the name Boerhavia golden mosaic virus (BoGMV) is proposed. Infectious cloned BoGMV DNA-A and DNA-B components induced golden mosaic symptoms in agroinoculated B. erecta plants, thereby fulfilling Koch’s postulates for this disease. Agroinoculation and mechanical transmission experiments revealed that BoGMV has an unusually narrow host range, limited to members of the family Nyctaginaceae and not including the permissive host Nicotiana benthamiana. The inability of BoGMV to infect N. benthamiana was due to a deficiency in cell-to-cell movement but not to a unique amino acid residue in the movement protein.