Selection Of Suitable Host Trees

The resistance phenomenon is of critical importance for an effective mistletoe cultivation. The hypothesis that resistance of oaks could be overcome only by the virulence of selected mistletoe seed could be ruled out. Seeds from any hardwood mistletoe (V. album ssp. album) could become established on mistletoe-receptive oaks. It was found that mistletoe resistance appears to be genetically fixed by the host tree (Grazi and Urech 1983). The work of Frochot et al. (1978) had already suggested that the resistance might be bound up with the trees' genetic constitution.

The oak mistletoe cultivation methods given below thus all depend on mistletoe receptive parent trees.

1. Sowing mistletoe on mistletoe-bearing oaks in natural sites: A naturally weak mistletoe distribution potential is made up for by applying vital mistletoe seeds to young branches of mistletoe oaks growing in the wild (Table 1).

2. Grafting: Scions of mistletoe-bearing oaks are grafted on to any oak material of local origin. Depending on scion quality and care taken, the proportion of mistletoe-bearing progeny may be up to 100%. The growing trees will, however, assume the "physiological age" of the scions, which may limit growth and the sustainability of mistletoe production.

3. Rooting mistletoe-bearing oak cuttings: This requires considerable experience in biology and technical equipment. Very much as with grafting, growth and mistletoe production are likely to be limited if cuttings are of a greater physiological age.

4. Sowing acorns from mistletoe-bearing oaks: This yields a relatively high percentage of mistletoe-receptive progeny (12-19%, Table 4). The method of choice is lining out in nursery style, as selecting suitable specimens will require little space. Oak

Table 4 Percentage of V. album-receptive oak seedlings among progeny of mistletoe-bearing parent trees.

Seed provenance

Parent trees

n

Mistletoe receptive seedlings

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