The orchard establishment, growth and precocity of four micropropagated apple scion cultivars

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Abstract
Self-rooted trees of Cox’s Orange Pippin, James Grieve, Greensleeves and Golden Delicious apple cvs, produced by micropropagation in vitro in 1978, were planted in April 1979 in a field trial to compare them with trees of the same cultivars produced conventionally by budding onto M.9 and MM. 106 rootstocks in 1977. The micropropagated trees were much smaller at planting than the (older) conventional trees, and although they all were difficult to establish and grew slowly in the year after planting their subsequent performance varied greatly between cultivars. Greensleeves on its own roots was less vigorous (up to five years of age) than Greensleeves on MM. 106 although it was somewhat more vigorous than Greensleeves on M.9. It flowered in the year after planting (1980), and in the subsequent years produced as many or more flowers and fruits per unit length of branch as did the Greensleeves on M.9 and MM. 106. James Grieve on its own roots was much more vigorous in absolute terms and relative to its vigour on M.9 than was Greensleeves, and also showed relatively precocious cropping. Flowering of the own- root trees was profuse in 1981 and flowering and fruit set per unit length of fruiting wood in 1982 were similar to that on M.9. Golden Delicious on its own roots gave trees of similar size to those on MM. 106 by 1982, and though it flowered in the second year after planting the fruiting per unit length of wood was much less than that of Golden Delicious on M.9 or MM.106. Cox on its own roots was almost as vigorous as Cox on MM.106 and flowered and cropped poorly in relation to tree size. The use of daminozide on the micropropagated trees of all cultivars increased their precocity and cropping efficiency in relation to tree size. Fruits on the own-root trees were typical for their cultivars except that those of own-root Golden Delicious were more russeted than those on M.9 or MM.106.

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