Bean Pod Mottle Virus (BPMV) Viral Inoculation Procedure in Common Bean (Phaseolus vulgaris L.)

Viral vectors derived from the Bean pod mottle virus (BPMV) were shown to be highly efficient tools for functional studies in soybean (Glycine max) and common bean (Phaseolus vulgaris) (Zhang et al., 2010; Diaz-Camino et al., 2011; Pflieger et al., 2013; Pflieger et al., 2014). Indeed, BPMV-derived vectors enable successful foreign gene expression analysis as well as virus-induced gene silencing (VIGS) but the delivery procedure of the viral vector into plants (i.e. primary inoculation) is a critical step. It can be achieved by various techniques such as Agrobacterium-mediated infiltration (agro-inoculation), mechanical inoculation of in vitro transcribed RNA, or biolistic delivery of infectious plasmid DNA (i.e. a DNA plasmid carrying a cDNA copy of the modified viral genome under the control of a 35S promoter). These delivery methods may be incompatible with large-scale functional studies (Pflieger et al., 2013). Here, we present the protocol for rapid, cheap and simple mechanical inoculation of BPMV vectors by direct rubbing of infectious plasmid DNA (direct DNA rubbing). Once infected plants are obtained, we used a classical protocol of mechanical inoculation using infected leaf sap to inoculate new healthy common bean plants (i.e. secondary inoculation).