Step 1: A common method to remove viruses from vegetatively propagated crops is meristem tip culture, since the apical meristem region is largely free of virus particles even in an infected plant.
Step 2: Sood and Palni carried out their tissue culture based virus elimination work on potato, which belongs to the genus Solanum, a crop where virus-free planting material is agriculturally very important because potato is propagated through tubers that easily carry viruses forward.
Step 3: Lycopersicon (tomato), Lilium and Penisetum are not the genus associated with this particular study, so the correct choice is Solanum sp.