By which of the following methods can a disease free plant be produced?

Tissue culture (micropropagation) is the most effective method for producing disease-free plants because it uses meristematic tissue (meristem tips) that is typically free of viruses and pathogens. The process involves excising very small meristem tips (0.1-0.5 mm) from shoot tips and culturing them in sterile nutrient media under controlled conditions. Vegetative methods like grafting, layering, and cutting can transmit diseases from the parent plant to the offspring since they use larger portions of infected plant material.