ALBERT

Description: Inheritance of allozymes of 12 polymorphic loci was demonstrated using haploid megagametophytic tissues of viable seed from a total of 47 white spruce trees in one stand. In general, allozymes segregated as expected in a 1:1 ratio. However, one allozyme of phosphoglucose isomerase (Pgi-2) did not segregate as expected. Significant deficiency in two different heterozygous combinations was observed. This result could be indicative of selection against the allozyme. The level of genetic variability in this stand of white spruce was similar to average levels of variation observed with many conifer species. Overall, an excess of heterozygotes was observed in the mature population. However, after 9 years of storage in a seedbank, no more than random selfing could be detected in the viable filial generation. Significant heterogeneity in allele frequency distribution of several loci was observed in the pollen pool in this stand. The calculated ratio of genetically effective males to females in this population was only 0.4. These results were interpreted as evidence for changes in the spatial genetic structure of the population, likely marking demes of related individuals, and restricted effective transmission distances of male gametes. Some implications for tree improvement programs are discussed.

Description: The effects of stratification, clipping, sulfuric acid soaking, and pericarp removal on the germination of hop-hornbeam (Ostryavirginiana [Mill.] K. Koch) seeds were investigated. Untreated seeds failed to germinate. Removing the pericarp produced 34–37% germination. Gibberellic acid (GA3) improved germination of intact seeds, but was most effective for seeds with pericarps removed, resulting in 76–80% germination. Although stratification of intact seeds for 3 months produced 15% germination, a combination of pericarp removal, GA3 treatment, and stratification was best, resulting in 81% germination. For seed testing, the pericarps should be removed and seeds treated with 500 mg/L GA3 for 24 h at 20 °C. Germination at 20 °C with continuous light appears to be a good test condition.

Description: Time is a major constraint in the progress of tree improvement programs. Four ways in which time influences the tree improvement process are (i) evolutionary time, (ii) time to harvest, (iii) time to achieve phenotypic stability, and (iv) time to reach reproductive maturity. The ways in which each of these affects the three phases of a tree improvement program (conservation, selection and breeding, and propagation) are identified and discussed. How biotechnological techniques, as well as other enabling technologies, address the time constraint problem is also discussed. The biotechnological approaches include tissue culture, molecular genetics, and genetic engineering; the enabling technologies include early testing and flower induction. Through tissue culture it is possible to increase genetic gain per unit time and increase total genetic gain by using more of the total genetic variation. Development of high-resolution linkage maps, through application of molecular genetics technology, will provide new approaches to early screening, testing, and selection. Additionally, molecular probes will be useful in improving methods that genetically fingerprint germ plasm. Genetic engineering has considerable potential to reduce time constraints. However, because of the diverse breeding and production populations typically employed, much basic work needs to be done to integrate genetically engineered materials into tree improvement programs. Early selection and flower induction address the time constraints imposed by age-stable performance and reproductive maturity. When used in combination with the previously described biotechnologies, a powerful system is created that can dramatically reduce the time required to integrate genetically improved material into forest regeneration programs. An example of integrating tree improvement, clonal forestry, and biotechnology is described for an existing black spruce regeneration program.

Description: Electrophoretic techniques which can be used to aid the identification of clones are described. An example using members (putative ramets) from 10 morphologically distinct putative clones of trembling aspen is presented. In this example, it is demonstrated that phenotypically uniform groups of trees (putative clones) can actually be composed of several electrophoretically distinct genotypes.

Description: Isoenzymes of esterase (EST), glutamate-oxaloacetate transaminase (GOT), leucine aminopeptidase (LAP), and peroxidase (PER) were examined following various periods of imbibition and germination of lodgepole pine (Pinuscontorta var. latifolia Engelm.) seeds. The acidic and basic isoenzymes of embryos, and roots and shoots of germinating seedlings were analyzed by polyacrylamide gel electrophoresis. One major band of EST disappeared with imbibition, while some minor bands appeared and disappeared with imbibition and germination. Comparison of the roots and shoots after 7 and 14 days of germination showed several tissue-specific differences. The number of bands of GOT increased with imbibition and germination. The levels of activity of three isoenzymes differed between the root and shoot tissues. One band of LAP disappeared with imbibition. The levels of activity of two bands varied between the root and shoot tissues. The number of bands of PER increased dramatically following imbibition and germination. Also, many tissue-specific differences were observed between root and shoot tissues.

Description: Isozyme characteristics were examined for eight enzyme systems in five 50-tree populations of balsam poplar (Populusbalsamifera L.) collected at longitude 90°W, from latitudes 45 to 55°N. Fifty-four percent of the trees were polymorphic at one or more loci, and 8 of the 17 loci examined were polymorphic in one or more populations. Average heterozygosity was low (0.037) and varied little among populations (0.025–0.043). No significant departure of multilocus genotypic proportions from those expected under random mating was observed. Genetic distances and F-statistics indicated that there is little genetic differentiation among populations in terms of the observed enzyme systems.

Description: Electrophoretically demonstrable diversity of 11 enzymes encoded by a total of 16 structural loci was analyzed in 22 sexually mature populations of Alnuscrispa (Ait.) Pursh (green alder, Betulaceae) in central Quebec. On average, 45% of the loci per population were polymorphic, with a mean of 2.39 alleles per polymorphic locus. Approximately 5% of the total genetic diversity resided among populations, with a mean genetic distance between populations of 0.01. Most populations thus appeared homogeneous, likely linked by high gene flow, as demonstrated by analysis of conditional average frequencies of alleles. Geoclimatic similarity among sites was also considered as a possible contributing factor to this apparent homogeneity. Heterogeneity of allele frequencies among populations was noted at seven loci. However, the presence of four populations that appeared to be more differentiated accounted for much of the observed heterogeneity. The early successional nature of this species and the partial isolation of these four populations seemed the most likely factors causing the observed differentiation.

Description: Levels of electrophoretically detectable variation at 19 loci were estimated in 36 populations representing the natural range of Larixlaricina (Du Roi) K. Koch. Results of this survey indicated that the species has levels of genic variation comparable with those of other species of woody perennials with extensive transcontinental ranges. There was no evidence of significant departures from Hardy–Weinberg expectation. However, on average, populations of this species were more differentiated and more genetically divergent from one another compared with many randomly mating tree species. A discriminant analysis of the genotypic structure of the populations analyzed indicated a general east versus west pattern, with populations in the Great Lakes basin being further differentiated. Present-day population distribution, population density, and reinvasion routes after the last glaciation could account for the observed patterns of genic variation.

Description: Linkage analysis, using megagametophytes from a clonal seed orchard of black spruce (Piceamariana (Mill.) B.S.P.) detected a tight association between Pgi-2 and Aat-1 with a recombination frequency of 2.6%. This is in marked contrast to earlier estimates for this species, which were much greater. The present results suggest that black spruce may be comparable with numerous other conifer species demonstrating this particular, highly conserved association.

Description: Isozyme markers were used to study the mating system, estimate the effective population size, and determine the effective gene pool composition in a black spruce clonal seed orchard. Ten seeds per family were electrophoretically analyzed by embryo and megagametophytic pairs to determine their allelic and genotypic frequencies at five polymorphic loci. Single-locus estimates of outcrossing ranged from 0.682 to 1.087 (mean, 0.942), while the multilocus estimate was 0.837. The variance effective population size was calculated to be 17 individuals, comprising 13 receptive females and 4 effective males. Evidence of gene pool heterogeneity suggested a small, nonrandomly mating population within the clonal seed orchard.