Sensitive detection of banana bunchy top and faba bean necrotic yellows viruses from infected leaves, in vitro tissue cultures, and viruliferous aphids using polymerase chain reaction

DNA primers for banana bunchy top virus (BBTV) and for faba bean necrotic y ellows virus (FBNYV) were constructed based on the nucleotide sequence of D NA component 1 of each virus that contains the viral putative replicase gen e. Three pairs of primers for each virus were utilized for standard polymer ase chain reaction (PCR) or immunocapture (IC) PCR amplification. DNA fragm ents of 439, 446, and 476 bp were amplified from extracts of BBTV-infected banana leaves, in vitro tissue culture, and viruliferous aphids. DNA fragme nts of 487, 931, and 1002 bp from extracts of FBNYV-infected faba bean plan ts and viruliferous vectors were also amplified. The amplified DNA fragment s were identified by size, nucleotide sequence, and (or) hybridization anal ysis. Virus-specific DNA fragments were absent from amplified extracts of u ninfected banana and faba bean tissues as well as from non-viruliferous aph ids. The nucleotide sequence of the PCR-amplified major portion (923 nucleo tides) of BBTV DNA component 1 of an Egyptian isolate has been determined. The sequence is 99% homologous to the Australian isolate of BBTV.