Bean golden mosaic geminivirus type II isolates from the Dominican Republic and Guatemala : nucleotide sequences, infectious pseudorecombinants, and phylogenetic relationships

Bean golden mosaic geminivirus (BGMV) causes major losses on beans (Phaseolus vulgaris) in the tropical and subtropical Americas and the Caribbean Basin. Infectious DNA-A and -B components of BGMV isolates from the Dominican Republic (BGMV-DR) and Guatemala (BGMV-GA) were sequenced, and their genome organizations were similar to those of other whitefly-transmitted geminiviruses from the Western Hemisphere. Whiteflies (Bemisia tabaci) transmitted BGMV from beans infected by particle-gun inoculation with clones of BGMV-DR or -GA. Infectious pseudorecombinants gave symptoms typical of wild-type infections when mixtures of BGMV-GA DNA-A and BGMV-DR DNA-B were used. Delayed and attenuated symptoms were obtained when mixtures of BGMV-DR DNA-A and BGMV-GA DNA-B were used. Phylogenetic analyses using the common region and four open reading frames placed 20 geminiviruses in eight clusters for the Western Hemisphere and at least five clusters for the Eastern Hemisphere viruses. BGMV-DR and -GA are in the BGMV type II cluster with the BGMV isolate from Puerto Rico. The BGMV type II cluster is clearly distinct from the BGMV type I cluster, which contains the BGMV isolate from Brazil. Bean dwarf mosaic geminivirus is in the Abutilon mosaic virus cluster, and bean calico mosaic geminivirus is in the squash leaf curl geminivirus cluster. Conserved nucleotide sequences of the common regions of members of these clusters were identified, and the presence of amino acid motifs with putative functions were identified in the derived amino acid sequences of the replication-associated proteins of BGMV-DR and -GA. The availability of sequenced, infectious clones of BGMV-DR and -GA provides opportunities for the study of genome functions and for the engineering of beans for resistance to these viruses.