Tissue cultures of plant organs offer excellent substrate for culturing and propagating the obligate fungi under defined conditions. For the first time, dual culture of downy mildew fungus and its host vine was successfully accomplished by G. Morel. Thereafter, numerous reports of dual and axenic cultures of biotrophs, especially rusts and downy mildew fungi, appeared in the literature. Although a few reports indicate successful establishment of recalcitrant powdery mildew fungi on their host callus, balanced growth in dual cultures has not been obtained so far. Ingram considered dual cultures valuable for the maintenance of supplies of aseptic inoculum, the cloning of isolates, and their safe international transport. The growth condition of a callus at the time of inoculation with a fungal inoculum is important and depends on the objective of the study. Initial attempts on the dual culture of fungi were mainly confined to the culture of obligate fungi on their host callus.