Calopogonium golden mosaic virus Identified in Phaseolus vulgaris from Western and Northern Regions of Costa Rica

Abstract

Bean golden yellow mosaic virus (BGYMV, GenBank Accession No. M91604) is reported to be the main bean-infecting (Phaseolus vulgaris) begomovirus in Central America (1,2). Another begomovirus, Bean calico mosaic virus (BCaMV, GenBank Accession No. AF110189), is known to infect P. vulgaris in central Mexico. Bean samples with the viral symptom of foliar chlorosis were collected in different regions of Costa Rica from 1994 to 2001. Total nucleic acids were extracted and tested using polymerase chain reaction (PCR) with degenerate primer pair PBL1v2039/PCRc2 for DNA-B, which can give a different fragment size for some begomoviruses (4). PCR fragments were obtained from 119 bean samples. Fifty samples from the central valley produced 600-bp PCR fragments, which is typical for BGYMV (4), and one sample produced two fragments (500 and 600 bp). One sample from western Costa Rica had a 550-bp fragment, and 69 samples from the western and northern regions produced 500-bp fragments. One of the latter samples (No. 01-1152) was selected for PCR with degenerate primer pairs PAL1v1978/PAR1c715 for DNA-A and PBL1v2039/PBR1v800 for DNA-B (4). The amplified PCR fragments were 1.35 and 1.4 kb for DNA-A and DNA-B, respectively. These are expected sizes for a Western Hemisphere begomovirus. The DNA-A fragment was cloned and sequenced (GenBank Accession No. AF439402). Sequence comparisons indicated that this uncharacterized begomovirus (No. 01-1152) had 98, 97, and 93% nucleotide identities with the rep gene, common region, and coat protein gene promoter of Calopogonium golden mosaic virus (CalGMV, GenBank Accession Nos. AF439748 and AF439749, respectively) (3). CalGMV had been isolated from a weed, Calopogonium sp., collected in 1991 near Quepos in the west and Tilaran in the north of Costa Rica (3). Phylogenetic analysis of the viral sequence of the begomovirus associated with No. 01-1152 placed it in the Squash leaf curl virus clade (1). BCaMV is also in this phylogenetic clade, but sequence comparisons between CalGMV and BCaMV had <90% nucleotide identity, and so are distinct species. CalGMV is the begomovirus associated with No. 01-1152, and this is an example of the movement of a weed-infecting begomovirus into an agricultural crop. Since this Calopogonium sp. is widespread in Central America, it is important to determine if CalGMV is present in beans in other regions. The data also indicate that BGYMV and CalGMV infect beans in two geographically distinct regions of Costa Rica. References: (1) J. C. Faria et al. Phytopathology 84:321, 1994. (2) W. McLaughlin et al. Plant Dis. 78:1220, 1994. (3) M. R. Rojas et al. Annu. Rep. Bean Improv. Coop. 35:150, 1992. (4) M. R. Rojas et al. Plant Dis. 77:340, 1993.