Banana bract mosaic disease (BBrMD) caused by banana bract mosaic virus (BBrMV) of the genus Potyvirus is one of the major constraints in banana and plantain production. This disease was first reported in the Philippines in 1979 10 and subsequently has been reported from several banana-growing countries including India, Samoa, Sri Lanka, Thailand, Vietnam, Colombia, Ecuador and Hawaii 20 indicating that this pathogen can spread quickly and cause significant economic losses worldwide. It has been documented that the yield losses due to BBrMV ranged from 30 to 70 % under natural field conditions in India and the Philippines respectively 10, 14. In India, BBrMD has been recorded from several banana growing states and is identified as one of the diseases of national importance 1-2. Use of quality tissue culture (TC) banana planting material is very important for enhanced production and productivity of banana.
It is necessary to ensure the growers to have access to quality virus free mother plants that have undergone virus indexing for producing healthy and high-yielding planting material 15. In 2007, the National Certification System for Tissue Culture Raised Plants (NCS-TCP) has been implemented by Department of Biotechnology, Government of India and it is first of its kind in the world (http://dbtncstcp.nic.in/) for certifying the banana plants for quality. Several methods have been developed and used for the detection of BBrMV, including electron microscopy, enzyme-linked immunosorbent assay (ELISA), dot immune-blot assay (DIBA) and reverse transcription polymerase chain reaction amplification (RT-PCR) 13, real-time RT-PCR and reverse transcription loop-mediated isothermal amplification (RT-LAMP) 16,20.
However, these methods are time-consuming, require technical expertise and laboratory equipments, which limit their application for onsite detection. A rapid, specific, user-friendly, field-deployable test kit that detects BBrMV allows banana grower or tissue culture banana producers to test the mother plants for BBrMV infection without any idea on this disease and assess if management practices are needed. The lateral-flow immuno assay (LFIA) is a method based on immuno-chromatography that use metal nanoparticles for colorimetric detection of targets. In LFIAs, gold nano particles (AuNPs) are the most commonly used visual readout detection labels. LFIA has been reported for a few plant viruses namely carnation mottle virus (CMV), bean mild mosaic virus (BMMV), tobacco mosaic virus (TMV), potato virus X (PVX), potato virus Y (PVY), plum pox virus (PPV), lily symptomless virus (LSV), lily mottle virus (LMoV), Soybean mosaic virus (SMV), citrus tristeza virus (CTV), large cardamom chirke virus (LCCV), citrus yellow vein clearing virus (CYVCV) 3-5, 7-8,11-12,18-19, 21.
In this study, a highly practical, rapid, user-friendly LFIA test was developed for the detection of BBrMV. This assay can be used to detect BBrMV in infected symptomatic and non- symptomatic banana leaf samples, seeds and different plant parts but was shown not to cross react with other viruses tested. Thus, the developed LFIA provides a powerful tool for rapid and simple onsite BBrMV detection and could prove to be a boon to the banana industry.