Step 1: Viruses that infect vegetatively propagated crops accumulate in older tissue but rarely reach the actively dividing cells at the very tip of the shoot apex, which is the biological basis of meristem culture for virus elimination.
Potato, scientifically Solanum tuberosum, is one of the most important crops where this technique is applied commercially because tuber propagation otherwise carries viral disease from one generation to the next.
Sood and Palni's 1992 work applied this meristem tip tissue culture approach specifically to Solanum, ruling out tomato (Lycopersicon), Lilium and Penisetum as the genus in question. Answer: Solanum sp.