DIGITALNA ARHIVA ŠUMARSKOG LISTA
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| ŠUMARSKI LIST 1-2/1966 str. 74 <-- 74 --> PDF |
PRESERVATION OF GENE POOL IN FOREST TREE POPULATIONS (Invited paper) by RYOOKITI TODA Government Forest Experiment Station, Kyusyu Branch, Kumamoto, Japan. It is not necessary to say much about the importance of the protection against loss of useful genes under the influence of tree breeding programs and intensive forest management. Breeding always involves selection which results in the loss of some genes. By selection, we intend, of course, to retain favorable genes and to discard unfavorable ones, but it is inevitable that many useful but still unknown genes may be lost in the process. Favorable genes are also lost through the negative selection which is rather commonly practiced in commercial forestry. It is, therefore, urgently needed that some action be taken to prevent the extinction of the hidden genes and to keep the gene pool large enough for future improvements. There are two ways to obtain this goal: one is the conservation of mature stands, either natural or artificial, and the other is establishing special new stands for the preservation of a broad gene pool. The first could be said to be a static method. It does not require any actual operation other than preserving nice stands in virgin forests or excellent plantations. Each reserve stand should desirably be made up of more than ten thousand individuals, which must be excluded from commercial utilization. Because of the large numbers of trees needed, there is considerable opposition against such reservation, and it is very difficult to designate such stands solely for use in forest genetics. Therefore, any stand reserves must be connected with natural protection promoted from the view point of public health, recreation, protection of wild life and natural monuments. The second method involving establishment of special stands is a dynamic one. Here, there is no need to reserve stands from a commercial forest, but it is only necessary to collect seeds from superior stands and to establish new stands from these. The newly established stands can then be commercially utilized when they become mature after the next generation has been established from their seeds. It is not difficult, therefore, to get support of the commercial forest management organizations for this approach. In a population for which the gene pool is to be preserved, seeds must be collected in a rich seed year on scattered seed trees. There should be forty, fifty or more such trees, each better than average in vigor and quality. Trees not selected as seed trees contribute their genes to the next generation through their pollen. Selecting this many mother trees in every generation should involve little risk of inbreeding in later generations (Stern , 1959). If the |