For what its worth, there is nothing wrong with the statement that the change in pigmentation could be caused by a virus. Virus can and do change host DNA and RNA by injecting their own genetic material into the cell . If a virus were to infect a plant at a node where cellular replication is taking place to produce leaves, stems and figs, the resulting alteration in DNA MIGHT result in a change in the physical attributes of the plant material. Although genetic mutations do occur for many reasons beyond virus infection, that is a possible vector for the change....