Serological and molecular detection of mixed bunchy top and mosaic virus infections in abaca (Musa textilis Nee)

Diagnosis based on symptoms does not clear distinguish diseases of abaca caused by mixed infections of different viruses causing bunchy top and mosaic diseases. Reliable diagnosis requires more sensitive serological and molecular detection methods. Thus, the occurrence of mixed bunchy top and mosaic virus infections in two abaca-growing areas in the Philippines was determined through selorogical and molecular virus detection. Abaca leaf samples collected from seven locations in the Bicol and Eastern Visayas regions [Philippines] were analyzed for the presence of Banana bunchy top virus (BBTV), Banana bract mosaic virus (BBrMV, Sugarcane mosaic virus (SCMV) and Cucumber mosaic virus (CMV). Serological detection by enzyme-linked immunosorbent assay (ELISA) of samples from all locations revealed the presence of BBTV, BBrMV, SCMV and CMV. BBTV, BBrMV, SCMV and CMV were detected in 92%, 71%, 62% and 26%, respectively of samples from the Bicol region. Likewise, these viruses were detected in most samples from the Eastern Visayas at frequencies at 100% for BBTV, 86% for BBrMV, 91% for SCMV and 85% for CMV. Infection occurred mostly as combination of two to four viruses detected in samples from both symptomatic and asymptomatic plants. Diseased plants exhibited varying symptoms, and that symptoms of single and mixed infections were not distinguishable. Molecular detection by polymerase chain reaction (PCR) and reverse transaction polymerase chain reaction (RTPCR) confirmed the presence of these viruses. BBTV was detected by PCR using DNA component specific primers, but detection was not consistent among the primers used. BBT1 and BBT2 primer pair detected the most number of BBTV positive samples. BBrMV by ELISA was not always consistent with PCR. The sensitivity of BBTV detection by PCR was affected by the dilution of the template DNA.