[in Japanese]

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In 1973, severe damage of planted Pinus strobus by an ascomycetous fungus was found in Tokyo University Forest, in Hokkaido, Japan. Apothecia and pycnidia were recognized on bark of dead branches and canker of the pine. This fungus was identified as Scleroderris lagerbergii GREMMEN Comparisons among specimens on Abies sachalinensis collected by YOKOTA, and by SAHO and author, and those on Pinus resinosa sent from DORWORTH, and those on P.strobus were made. In the perfect state, there were no clear defferences among them. But, conidia on P.strobus are mostly sickle-shaped, one to four celled, 32.0-3.0μ in average. On the contrary, conidia on Abies sachalinensis were sickle-sickle-shaped, four eight celled, 46.1-3.1μ. Therefore, the fungus on planted Pinus strobus may be another stain within S.lagerbergii, the same as the fungus reported by DORWORTH, ETLLINGER and GREHMN.

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Arust on Pinus pumila was found at the Tokyo University Forest in Hokkaido in 1972. Since then, field observations have noticed no alternate host plant around the rusted P.pumila. while, the mono-Caryotic condition of aeciospore germ tubes was recognized by the HCl-Giemsa stain. The monocaryotic condition is the same with that of germ tubes of Endocronartium harknesii(J. P. MOORE) HIRATSUKA, an autoecious rust. Therefore, the rust on Pinus pumila also may be a pine-to-pine rust.

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Resistance against vole-gnawing of Kurile larch (Larix gmelinii var japonica;Gk:ex Kurile;Gs:ex Saghlien), Japanese larch (L. laptolepis;L) and several hybrid families between them was put to test in the Winters cf 1971-'72 and '72-'73. Some of the hybrids were newly produced from the intercrossing of individuals of F_1 hybrid families and the back-crossing of them to trees of parental species since the last report of the senior author and his colleague. The degree of resistance was measured by the loss amounts of the test pieces which, in every pair or whole set of 8 hybrid families, were subjected to the gnawing of voles kept under isolated (1 vole in each of 14 chambers) or aggregate (7 voles in a chamber) conditions. Through the repeated and variously. combined experiments using young seedlings and saplings, through observation on a test plantation, and partly through comparison of the results of the present study and the former reports, the following facts are confirmed newly or again. (i) Among these hybrids, newly tested [(Gk×L)×(Gk×L)] and [(Gk×L)×L] are ranked in the resistance beside Korean larch. (Korean larch was of intermediate-class and praetically sufficient resistance and therefore used as a criterion (or standard) for its comparison in the former studies.) Their growth is also as good as that of F_1 hybrid families. (ii) Every interspecific hybrid inclines toward the parent with larger resistance against vole-gnawing, as mentioned formerly, and the back-crossed family gets so much close to the parental species. (iii) Within the variation of Kurile larch, two geographical races, i.e., Gk and Gs, should be kept separated from each other on the basis of the difference of their vole-resistance The former(GK) is doubtlessly of greater resistance than the latter. Naturally, there is still remained some possibility of detecting difference of resistance among provenences or populations within each race. (iv) One of the conclusions of the former report, that unilateral inclination or resistance toward maternal parent (usually considered in the rank of species or varieties) is recognizable between the families of reciprocal crossings of these two species, seems thus to be denied, with reservation of partial possibility of distinguishing such inclination among combinations of some races, provenances or individuals of parental species in the future studies. As a general conclusion, the hybrids of these two species are ranked according to their resistance as follows: L×L≫(Gk×L)×(Gk×L), (Gk×L)×L, L×Gs, Ga×L)>L×Gk, Gk×L>Gs×Gs, (Gk×L)×Gk>Gk×Gk

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[in Japanese]

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Seed lots were gathered from the trees with different forms of prostrate and erect types growing at various elevations of Mt. Fuji around its forest and timber lines and those with cones of non-recurvate scales like Korean larch. And the seedlings from them were investigated at the Tokyo University Forest in Hokkaido, in order to ascertain whether such tree forms are genotypic or phenotypic, and to examine the taxonomic entity of the individuals with such particular cones. Through observations and measurements of them at the nurse, stage and during the period. of about 10 years after planting out in experimental fields, the following facts became clear. (i) All progenies of mother trees of prostrate type compared quite well with those of erect type in their trunk form and vigorous growth, and did not include any single seedling of prostrate form. Moreover, there was not found any obvious correlation between the forms of mother trees and various characters of their progenies such as growth vigour, formation of lateral branchlets, time of terminal bud formation and that of autumnal colouring of needles. Therefore it is doubtless that this difference of tree forms is merely phenotypic. (ii) However, the progenies of the trees growing at high elevations more than 2300-2400m are to some extent different from those at lower elevations or those of artificial plantations at Yamabe in their formation of lateral branclaets (less), time of terminal bud formation and of autumnal colouring of needles (earlier for some days), and growth at the stage of 3-year-old. seedlings (worse). (iii) Generally speaking, the provenances in the district of Mt. Fuji are conspicuous among all those those put to the provenance test by their habit of spreading primary branches or limbs in the shape of obVious storeys like kurile larch. (IV) The progenies of trees with Korean larch-type cones were not distinguishable from those of ordinary type in the characters discussed in the preceding paragraphs. Therefore it is quite reasonable to consider that these trees are still within the range of morphological variation of Japanese larch with only small deviations from the typical. According to several reports as to provenance tests of Japanese larch, both in this and foreign countries, this species shows constant variation among provenances of geographical difference in frost-(and pest-) hardiness, flower-setting, some morphological characters, and others, but does not in the growth of progenies. The result of the present study suggests the same inclination as to the sources of altitudinal difference.

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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.

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[in Japanese]

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