A healthy C. campestris colony (*) was established on V. rosea plants, following the classic procedure described by BENNETT (1944). Subsequent growth of the parasite plant on fresh V. rosea constituted the stock supply. Five different types of sources of inoculum were taken into

consideration for the trials: a) two 8-year-old Golden Delicious trees with natural infection of AP, transferred to a plot close to the laboratory; the presence of MLOs in thin sections of their leaf tissues had been detected by e.m.; b) apple plants grown in pots, i.e. apple seedlings or Golden Delicious young trees, inoculated by root-grafting or by approachgrafting (REFATTI et al ., 1986) using infected material of the trees as in a); c) detachced twigs from the trees as in a), dipped with the basal end in vials of water, kept in the greenhouse; d) young sprouts showing the typical witches brooms growing from pieces of apple roots laid in a medium-grade washed sand, in a propagating heated bed of the greenhouse (Fig. 1); the infected roots, having a diameter of 2-5 cm, had been obtained from apple trees in the orchards; e) young potted apple of the Golden Delicious cultivar, obtained by micropropagation of tissues derived from the trees as in a) (Fig. 2); the plants were used at the average high of 10 to 15 cm and chosen from the ones showing evident symptoms of AP and having a good growth and succulent tissues. The two basic methods as follows were adopted in the APA transmission attempts. A) Dodder bridges established between donor and recipient plants. The parasitic plant derived from a healthy V. rosea host was established on the apple plants sources of inoculum (Fig. 3). About three weeks later, when the dodder was well grown (stems about 10 cm long) on the infected plants, one or a few stems were trained to healthy vigorous young V. rosea plants. The apices of the filaments were forced to remain in contact with the tissues of the test plant till they were wrapped around the stem and had formed hau