39. トドマツとシラベの種間雑種の諸特性(会員研究発表講演)

抄録

Young plants of Abies sachlinensis are frequently damaged by late frosts on their buds in the course of opening for all its nativeness to Hokkaido, especially when planted in wide clear-cut area. For the purpose of obtaining hardier fir plants through inter- and intraspecific hybridization, a number of crossings were carried out between the selected trees of A. sachalinensis and those of the same species, A. veitchii and A. mariesii in 1963(A) and 1969(B) (cfr. Table 1 and Figure). A. veitchii, among these species, was already noticed by its late opening of leaf buds and considerable hardiness in sample plantations. The hybrid families were repeatedly observed or measured, and recorded about the periods of opening of leaf buds, hardiness to late frosts and growth in size and in vigour, during their nursery stage and after planting out in the breeding arboretum. The 5-year-old seedlings of the (A) set were also put to laboratory test of vole-gnawing in the winter of 1968〜'69, because it was known that plants of the species of Honshu were heavily gnawed byvoles. The following facts have been noticed from these observations and experiments. (i) With respect to the period of leaf bud opening, all the interspecific hybrid families are close to the parental species of late opening, and they are able to escape from the injury of heavy late frosts. On the other hand, the families of intraspecific crossings with the pollen trees selected for the lateness of bud opening do not improve much in this character. (ii) It is difficult to point out any common tendency in differences of growth in size between interspecific and intraspecific hybrid families, but rather the progenies of different maternal trees seem to be different from each other. Though the interspecific and intraspecific hybrid families are thus comparable with each other in the figures of size growth (cfr. Table 3 and Figure), the former families look more healthy and vigorous than the latter in their actual appearance. (iii) The interspecific hybrids are highly evaluated also in their vole-resistance nearly comparable with that of the parent of larger resistance, A. sachalinensis. The hybrids, especially between A. sachalinensis and A. veitchii, whose value for practical fir-forestry in Hokkaido has been thus proved, are producible at a considerablly high rate through open pollination because of the simultaneity of, flowering or pollen dispersal and high compatibility of both species. But by the same reason, one must take care to avoid bad effect of introducing hastily these hybrids into the natural regeneration system of A. sachalinensis forests in Hokkaido.