DIGITALNA ARHIVA ŠUMARSKOG LISTA
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ŠUMARSKI LIST 1-2/1966 str. 110 <-- 110 --> PDF |
HETEROSIS Genus Pinus: Is exhibited in the hybrid P. strobus x griffithii, which is also resistant to blister rust. The hybrid P. densiflora x P. thunbergii also has hybrid vigor; data are not available on its rate of growth in Japan. Other hybrids with this characteristic include P. nigra x P. resinosa, P. thunbergii x P. nigra, P. ponderosa x P. engelmannii, P. ponderosa x P. montezumae, P. echinata x P. rigida, P. contorta ssp. latifolia x P. banksiana. M o u 1 o- p o u 1 o s and Bassiotis (37) established that the hybrid betwen P. halepcnsis and P. brutia grows faster than either parent at the age of 9 year?. Genus Abies: In Bavaria two hybrids display intensive luxuriant growth (47). A cross Abies Veitchü x A. alba, 11 years old, is 205% taller than its female parent and 301% taller than its male parent. A hybrid A. concolor x A. Veitchii is taller than its female and male parent by 162% and 204% respectively. Rohmede r stresses that the intensive growth of the hybrid not only depends on the combination of suitable species but also on the individuals used in crossing. Besides, in hybrids of fir high resistance to cold is more important than growth rate. In the genus Picea the hybrids displaying heterosis are: P. glauca x P. engelmannii and the reciprocal, and the hybrid between the species P. glaucaand P. jezoensis. According to our investigations (56), the cross between Omorika spruce and Sitka spruce surpasses Omorika spruce in growth at the age of 5 years. According to Langne r (33), a 2-year-old hybrid between these two species exhibits a heterotic effect, while the older hybrids from a previous experiment do not show this character. Genus Larix: The best known is the hybrid between L. decidua and L. leptolepis, which was first established in Scotland. Many papers have been published dealing with the hybridization of these two species. Thus for instance in Denmark, L a r s e n (34, 35) carried out extensive investigations on hybridization between the mentioned two species. In Germany we may mention Dimpflmeier (11), Langner (3,0 32) and Go the (20). In Yugoslavia Vidakovi ć (53, 54) works on the hybridization of larch. In all cases it was shown that the hybrid larch is strongly heterotic, and in addition is resistant to the canker. The hybrid between the Siberian and Japanese Larch is interesting for the Scandinavian countries and the U.S.S.R. Albenski j (1, 2, 3) established the phenomenon of heterosis in this hybrid as well as in the hybrid between the European and Japanese Larch. According to Rohmede r (47), the hybrids L. decidua x L. gmelini, and L. decidua x L. gmelini var. principis Ruprechtii also exhibit the phenomenon of heterosis. In the genus Pseudotsuga, C h i n g (8) obtained by crossing P. taxifolia x P. macrocarpa hybrid plants which at the age of 2 years were larger than their parents. The genus Populus has the well known characteristics that may of its species are easy to cross and that the pure species as well as the hybrids are easily propagated from cuttings. Many natural crosses are well known in poplars. Thus, for instance, several very valuable clones such as 1-214 and 1-156 were selected in Italy from spontaneous crossess between P. deltoides and P. nigra. These clones are successfully grown in Italy and the neighbouring countries. We can be certain that these clones possess hybrid vigor |