Treesearch

A simple method of mass-producing shortleaf x slash pine hybrids was attempted. Large quantities of slash pine pollen were spread on unbagged shortleaf flowers in the hope of recovering a high percentage of hybrid progeny and thus materially reducing the cost of producing such hybrids by conventional controlled pollination. The hybrid is very promising, but, as Snyder and Squillace (1965) have shown, seed yields from controlled pollinations have averaged only 8.5 sound seeds per cone.

The source of seed is an important consideration in the reforestation program on the National Forests in the North Central Region. Thirty-five seed production areas have been set up in the Region, along the lines proposed by the North Central Forest Experiment Station, to provide control of seed source. Red pine, white pine, shortleaf and loblolly pine, and white spruce areas have been established. Including isolation zones, 1.500 acres are involved. Anticipated average annual yield is about 2,000 pounds of cleaned seed.

Homozygous trees will never be the desired ultimate step in a forest tree improvement program. However, they will serve many purposes in forest genetics research: (1) in the detection of genetic markers; (2) in the isolation of traits under simple genetic control for the study of growth and differentiation phenomena; (3) as a tool as well as reference material in the study of breeding mechanisms in natural populations; (4) as reference material in a study of the efficiency of different selection schemes; and (5) in the study of sex control mechanisms in dioecious species. Furthermore,...

Within-species variation in turpentine composition has promise of great utility in pine genetics. Most of the early work on turpentine composition dealt with species differences, and the utility of such variation in the taxonomy of pines is well known (Mirov 1961). With the development of gas chromatographic techniques, intensive study of individual tree differences has become possible (Bannister et al. 1959; Williams and Bannister 1962); and this type of variation has been shown to occur in several pine species (Bannister et al. 1962; Blight and McDonald 1964; Smith, 1964a).

The initial size of conifer seedlings is closely related to seed size (Hadders 1963), and seed size is a maternal characteristic that is highly subject to environmental modification (Mergen et al. 1964; Righter 1945). The effect of seed weight must be accounted for in critical studies of seedlings which attempt to attribute differences in growth to specific genetic or environmental causes (Duffield 1960; Mitchell 1934, 1939).

Many seed orchard programs include a stage at which clones or seedlings are culled on the basis of progeny tests. Though breeding systems which involve progeny testing differ in efficiency, they all provide information on an individual's breeding value through its own performance and that of parental or seedling relatives. A combined index on any one trait, using information from a set of relatives, is desirable. However, tree breeders appear to be planning only limited use of indices on data from relatives. In so doing, they may be foregoing a considerable advantage, for the increased...

Readily identifiable phenotypes, such as cotyledonary chlorophyll deficiencies, whose genetic basis can be established, would be highly useful in forest genetics research as genetic markers. In the genus Pinus mutants with severe deficiencies, such as albinos, will die shortly after seed germination while those with less severe deficiencies will not. In either case, however, the symptoms appear in early stages of growth and hence these types of mutants are especially useful as gene markers.

One of the principles of experimental design is that replicates be relatively homogeneous. Thus, in forest research a replicate is often assigned to a single crew for planting in a single day on a uniform site. When treatments are numerous, a large area is required per replication, and homogeneity of site is difficult to achieve. In this situation, crop scientists (LeClerg et al. 1962) frequently divide the replicate into sub-blocks. The most used of the incomplete block designs are the lattices. Another type of incomplete block designs, the compact family block (Hutchinson and Panse 1937;...

In the genus Pinus, much of the information about species crossability that has accumulated during the past three decades has reinforced ideas about the relationships of pines based on other kinds of evidence. There are some conspicuous exceptions to this generalization, however, and the most thoroughly investigated of these exceptions is Jeffrey pine (Pinus jeffreyi Grev. & Balf. ), an economically important forest tree of montane California and adjacent parts of Oregon, Nevada, and Baja California. Biochemically, this puzzling species is much like the Sabinianae Loud. (Macrocarpae Shaw),...

Picea schrenkiana Fisch and Meyer is a relatively unknown central Asiatic species confined to the Ala Tau and Thian Shan mountains of Turkestan. Morphologically the species is most closely related to P. spinulosa (Griff.) Henry and, to a lesser degree, to P. obovata Ledeb. (Wright 1955).