Study on Seed Transmission of Abaca Viruses

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Study investigators: Leny C. Galvez Ph.D., Jose L. Catalla, Cris Francis C. Barbosa, Roxanne C. Sevilla

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In the Philippines, abaca is propagated through suckers, corms and tissue-cultured plantlets (Abaca Technoguide 2016). Due to the increasing demand for abaca fiber, a significant number of planting materials is required for abaca area expansion.  Use of seeds as planting material is currently being promoted to address the limitation for planting material (Abaca seeds propagation undated). A number of viruses, however, have been reported and reviewed to be transmitted through seeds. In other monocots like abaca, virus seed transmission was also documented e.g. Barley stripe mosaic virus (Jezewska and Trzmiel 2009), High Plains virus (Forster et al 2001), Maize dwarf mosaic virus (Tsai and Brown 1989).  Due to the massive negative impact of virus diseases in abaca plantations, determination of the presence of and possible transmissibility of viruses on seeds like ABTV and BBTV is of utmost importance, hence this study.

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Methodologies utilizing PCR are currently being developed for detection of viruses in abaca. PCR has been established as the new gold standard for detection of a wide variety of diagnostic target, including viruses (Mullis and Faloona 1987; Freymuth et al 1995). The reaction requires a pair (uniplex format) or multiple pairs (multiplex format) of oligonucleotide primers that are complementary to their target sequences within the genome of the diagnostic target.

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PCR has been the reference standard for the detection of virus and virus-like agents in planting materials and has been used to confirm results in virus indexing of planting materials which are initially screened for viruses using a serological technique e.g. ELISA. PCR has its advantage of high sensitivity and specificity than serological methods; however, this technique requires DNA templates with high quality and purity, thermal cyclers and electrophoresis equipment. The high inhibitor content in seeds could possibly cause false-negative results in the PCR reaction, thus, interfering in the detection of some seed infections. Another nucleic acid-based method called loop-mediated isothermal amplification (LAMP) could be used for more efficient disease management and to solve limitations in sensitivity. This technique is 100-fold more sensitive than PCR, and requires less expensive and less sophisticated equipment such as water bath and heat block (Notomi et al. 2000; Peng et al. 2012).

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The presence (usually a surface phenomenon; a contaminant) and transmission (classically in tissues inside of the seed coat; hence, transmission) of abaca viruses in seeds serves as a potential threat to the management of the disease. The objective of this study, therefore, is to determine the presence of ABTV, BBTV, SCMV and BBrMV in abaca seeds and their transmissibility to seed-derived plantlets using LAMP and PCR.

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