Browne's Blechum (Blechum pyramidatum) is a common weed found in fields and waste grounds in the Philippines. A disease was observed causing begomovirus-like yellow/chlorotic leaf veins and shortened internodes of Browne's Blechum plants on the island of Luzon, Philippines; disease incidence ranged from 10 to 50% in fields in 2012. Samples were collected from two plants with symptoms from each of Laguna and Quezon provinces and one plant without symptoms from Laguna Province. All four samples from plants with symptoms tested positive for begomovirus by PCR using primer pair PAL1v1978B/PAR1c715H (2), but the symptomless plant sample did not. However, no virus DNA-B component was detected in any of the samples using either general detection primer pair DNABLC1/DNABLV2 or DNABLC2/DNABLV2 (1). Using abutting primers AFPH12W1-R2F (TCTGGATCCATTGTTGAACGAGT) and AFPH12W1-R2R (CCGGGATCCCACATTGTTAAACA), a complete DNA-A component sequence was obtained for a Laguna isolate (GenBank Accession No. KF446659) and for a Quezon isolate (KF446660). The Laguna and Quezon isolate sequences were 2,764 and 2,756 nucleotides, respectively, and shared 90.6% nucleotide sequence identity. Both had six open reading frames (ORFs)—two in the virus sense (V1 and V2) and four in the complementary sense (C1 to C4)—and the geminivirus conserved sequence (TAATATTAC). Based on BLASTn searching of GenBank and sequence analysis using MEGALIGN (DNASTAR), both isolates should be considered as a new begomovirus (tentatively named Blechum yellow vein virus, BlYVV) since their DNA-A sequences share less than 89% nucleotide identity with any other begomovirus. Both DNA sequences had the highest nucleotide identity (84.8 to 87.6%) with Papaya leaf curl Guangdong virus isolates (AJ558122, AY650283, FJ495184, FJ869907, and JN703795). To our knowledge, this is the first report of a previously unidentified begomovirus associated with yellow vein disease of this species.
References: (1) S. K. Green et al. Plant Dis. 85:1286, 2001. (2) W. S. Tsai et al. Plant Pathol. 60:787, 2011.