Role of Potato mop-top virus RNA-TGB in pathogenesis and synergism with Colombian potato soil-borne virus

Abstract: Potato is one of the most important food crops in the world, providing staple food to variety of cultures around the globe. Due to its importance, pathogens affecting its production have a considerable impact on local economies, mainly in developing countries where the production relies on small farms. Potato mop-top virus (PMTV, pomovirus) is of economically importance in potato growing regions in temperate countries, were PMTV induces necrotic arcs in tuber flesh. A novel member of the pomovirus genus has been described co-infecting with PMTV in the South American Andes. Colombian potato soil-borne virus (CPSbV, pomovirus) induces mild mosaic on Nicotiana benthamiana leaves and twisting of the top leaves of the plant. Co-infection leads to additive effect of symptoms in N. benthamiana, which might lead to worsen the effect of PMTV if CPSbV is introduced to new territories. Here we studied the synergism of PMTV and CPSbV using infectious clones in binary vectors. N. benthamiana plants were agroinfiltrated with CPSbV RNA-Rep and PMTV RNA-TGB genomic components. As a result, it was not possible to detect CPSbV RNA-Rep, but PMTV RNA-TGB was detected from upper leaves, suggesting that there is genomic complementation of both viral species and that it can possibly happen in vivo. A system based on in vitro transcription of the clones under the T7 promoter and inoculation needs to be tested. Additionally, the effect of the pathogenicity factor PMTV 8k (Cysteine-rich protein) was evaluated in the potato host plant. N. benthamiana plants infected with full length PMTV infectious clones and PMTV infectious clones depleted of 8k ORF were used as scions for grafting into in vitro propagated potatoes (cv. Saturna). So far, the grafting was successful in 43,3%. The presence of the virus will be detected prior to transcriptome analysis.