Keywords: babuvirus, multiplex PCR, Musa textilis Née, virus detection Accurate Diagnosis of Multicomponent Babuviruses Infecting Abaca by Simultaneous Amplification of their Genome Segments 1 Philippine Fiber Industry Development Authority (PhilFIDA) PCAF Bldg., Department of Agriculture (DA) Compound Diliman, Quezon City 1101 Philippines 2 National Institute of Molecular Biology and Biotechnology University of the Philippines Diliman Quezon City 1101 Philippines *Corresponding Author: lcgalvez@huskers.unl.edu Cris Francis C. Barbosa 1 , Rhosener Bhea L. Koh 2 , Vermando M. Aquino 2 , and Leny C. Galvez 1 * Abaca bunchy top virus and banana bunchy top virus (ABTV and BBTV; genus Babuvirus; Family: Nanoviridae) are two of the most destructive abaca viruses. Uniplex polymerase chain reaction (PCR) and loop-mediated isothermal amplification (LAMP) are nucleic acid amplification techniques (NAATs) currently being used for their detection and diagnosis. However, the multicomponent nature of these bunchy top viruses has been documented to affect the diagnostic sensitivity of the aforementioned techniques, resulting in false-negative detection. This study, therefore, aimed to develop an assay that is strategic for accurate diagnosis of these multicomponent viruses. The multiplex PCR method was optimized at 56.5 °C annealing temperature (T A ), and was evaluated to have 91–100% diagnostic sensitivity and diagnostic specificity (CI = 95%, n = 60) against ABTV and BBTV – more accurate than LAMP and uniplex PCR. This paper provides evidence on the effect of the multicomponent nature of ABTV and BBTV in their detection even on techniques with superior analytical sensitivity such as LAMP. Moreover, it provides a strategic diagnostic tool to circumvent difficulties in the diagnosis of multicomponent abaca viruses. Philippine Journal of Science 149 (2): 373-382, June 2020 ISSN 0031 - 7683 Date Received: 04 Dec 2019 INTRODUCTION Abaca (Musa textilis Née) is a fiber crop native to the Philippines, though it is also widely distributed in humid tropical locations (Spencer 1953). It is one of the major agricultural export commodities of the nation, supplying 85% of the global demand for raw fiber and derived products, and generating a total of USD 111.5 M earnings in 2018. The abaca industry is one of the major sources of livelihood for nearly 1.5 M Filipinos. A total of 180,302 ha of land is being cultivated with abaca by 122,758 farmers (PhilFIDA 2018). The abaca fiber is the primary driving force for its cultivation. It is of global importance due to its great mechanical strength, resistance to saltwater damage, and long fiber length (Spencer 1953; Punyamurthy et al. 2014). The abaca fiber is utilized mostly in paper products, cordage, and handicrafts. It also used in automotive ”soft” 373