Transgenic Tobacco Lines Expressing Yam Mosaic Virus Coat Protein-Derived dsRNA Are Resistant to Yam Mosaic Virus

Yam mosaic virus (YMV), a Potyvirus, is a highly destructive pathogen of yam accounting for yield losses up to 40%. Apart from causing significant reduction in tuber size and quality, it restricts international exchange of germplasms. It thus becomes crucial to get resistant or at least virus-free planting materials for farmers. This study was aimed at inducing resistance to YMV in tobacco by RNA silencing. An RNAi construct containing 161 bp fragment of YMV-coat protein (CP) gene was developed and used to produce transgenic tobacco lines expressing YMV-coat protein (CP) derived double stranded RNA (dsRNA) via Agrobacterium-mediated transformation. Of the eight T1 transgenic lines inoculated with YMV, six (L1, L2, L3, L5, L7 and L8) showed immunity to YMV as no symptoms were detected, whereas two (L4 and L10) exhibited high resistance with mild symptoms limited to inoculation portions. No virus could be detected in uninoculated new leaves of the transgenic lines after RT-PCR and qPCR analyses of YMV-coat protein (CP). The presence of small interfering RNAs in transgenic lines after virus challenge indicates that the resistance was acquired through RNA silencing.