Abstract
The mating system of Douglas-fir [Pseudotsuga menziesii (Mirb.) Franco] was examined in two genetically similar seed orchard blocks with the aid of allozyme polymorphisms at six loci. The pollination environment (time of pollination and length of pollination season) of one block was manipulated by means of an overhead water spray cooling treatment. The cooling treatment temporarily delayed the pollination season in the treated block by 12 days relative to the untreated one. In addition, the length of the pollination season in the cooled block was shorter than the uncooled one by 12 days (18 vs. 30 days). The rate of inbreeding was significant in the uncooled block, while a perfect outcrossing rate was obtained for the cooled one. This difference was attributed to the low outcrossing rate obtained within the lower crown of the control block. It was concluded that the observed significant selfing in the uncooled block was caused by the first-pollination primacy that permitted related pollen to out-compete unrelated pollen in the extended pollination season. A shorter pollination season produced a dense pollen cloud of related and unrelated pollen, hence, early zygotic selection favoured unrelated embryos. An extended pollination season, on the other hand, permitted related pollen to succeed in pollination and fertilization without any challenge by unrelated pollen. Controllable variation in the rate of inbreeding reported in this study could be useful to improve the genetic quality of seed produced from seed orchards and consequently to maximize genetic gains from selections.
Similar content being viewed by others
Article PDF
References
Adams, W T. 1983. Application of isozymes in tree breeding. In: Isozymes in Plant Genetics and Breeding, Part A., Tanksley, S. D. and Orton, T. J. (eds), Elsevier, Amsterdam, pp. 381–400.
Adams, W T, and Birkes, D S. 1990. Estimating mating patterns in forest tree populations. In: Biochemical Markers in the Population Genetics of Forest Trees, Hattemer, H. H. and Fineschi, S. (eds) SPB Academic Publishing bv, The Hague, The Netherlands (in press).
Allen, G S, and Owens, J N. 1972. The Life History of Douglas-fir. Environment Canada, Forest Service, Ottawa.
Brown, A H D, Barrett, S C H, and Moran, G F. 1985. Mating system estimation in forest trees: models, methods and meanings. In: Population Genetics in Forestry, Gregorius, H. R. (ed.), Springer-Verlag, Berlin, pp. 32–49.
Clegg, M T. 1980. Measuring plant mating systems. Bio-Science, 30, 814–818.
El-Kassaby, Y A. 1981. Genetic interpretation of malate dehydrogenase isozymes in some conifer species. J Hered, 72, 451–452.
El-Kassaby, Y A, Edwards, D G W, and Cook, C. 1990a. Impact of crop management practices on seed yield in a Douglas-fir seed orchard. Silvae Genet, (in press).
El-Kassaby, Y A, Edwards, D G W, and Taylor, D W. 1990b. Effect of water-spray cooling treatment on seed germination in a Douglas-fir seed orchard. New Forests, 4, 3–12.
El-Kassaby, Y A, Fashler, A M K, and Sziklai, O. 1984. Reproductive phenology and its impact on genetically improved seed production in a Douglas-fir seed orchard. Silvae Genet, 33, 120–125.
El-Kassaby, Y A, and Ritland, K. 1986a. Low levels of pollen contamination in a Douglas-fir seed orchard as detected by allozyme markers. Silvae Genet, 35, 224–229.
El-Kassaby, Y A, and Ritland, K. 1986b. The relation of outcrossing and contamination to reproductive phenology and supplemental mass pollination in a Douglas-fir seed orchard. Silvae Genet, 35, 240–244.
El-Kassaby, Y A, Ritland, K, Fashler, A M K, and Devitt, W J B. 1988. The role of reproductive phenology upon the mating system of a Douglas-fir seed orchard. Silvae Genet, 37, 76–82.
El-Kassaby, Y A, Sziklai, O, and Yeh, F C. 1982a. Linkage relationships among 19 polymorphic allozyme loci in coastal Douglas-fir [Pseudotsuga menziesii (Mirb.) Franco]. Can J Genet Cytol, 24, 101–108.
El-Kassaby, Y A, Yeh, F C, and Sziklai, O. 1982b. Inheritance of allozyme variants in coastal Douglas-fir [Pseudotsuga menziesii var. menziesii (Mirb.) Franco]. Can J Genet Cytol, 24, 325–335.
Erickson, V J, and Adams, W T. 1989. Mating success in a coastal Douglas-fir seed orchard as affected by distance and floral phenology. Can J For Res, 19, 1248–1255.
Fashler, A M K, and Devitt, W J B. 1980. A practical solution to Douglas-fir seed orchard pollen contamination. For Chron, 56, 237–241.
Fashler, A M K, and El-Kassaby, Y A. 1987. The effect of water spray cooling treatment on reproductive phenology in a Douglas-fir seed orchard. Silvae Genet, 36, 245–249.
Franklin, E C. 1970. A survey of mutant forms and inbreeding depression in species of the family Pinaceae. USDA Forest Service, Research Paper SE-61.
Franklin, E C. 1974. Pollination in slash pine: first come, first served. In: Proceedings of a Colloquium, Seed Yield from Southern Pine Seed Orchards, Kraus, J. (ed.) Georgia Forestry Center, Macon, GA, pp. 15–20.
Hamrick, J L, Linhart, Y B, and Mitton, J B. 1979. Relationships between life history characteristics and electro-phoretically-detectable genetic variation in plants. Ann Rev Ecol Syst, 10, 173–200.
Owens, J N, Simpson, S J, and Molder, M. 1981. The pollination mechanism and the optimal time of pollination in Douglas-fir (Pseudotsuga menziesii). Can J For Res, 11, 36–50.
Owens, J N, and Simpson, S J. 1982. Further observations on the pollination mechanism and seed production of Douglas-fir. Can J For Res, 12, 431–434.
Ritland, K, and El-Kassaby, Y A. 1985. The nature of inbreeding in a seed orchard of Douglas-fir as shown by an efficient multilocus model. Theor Appl Genet, 71, 375–384.
Sarvas, R. 1962. Investigations on the flowering and seed crop of Pinus sylvestris. Comm Inst For Fenn, 53, 1–198.
Schemske, D W, and Lande, R. 1985. The evolution of self-fertilization and inbreeding depression in plants. II empirical observations. Evolution, 39, 41–52.
Silen, R R, and Keane, G. 1969. Cooling a Douglas-fir seed orchard to avoid pollen contamination. USDA Forest Service, Research Note PNW-101, 10 pp.
Webber, J E, and Yeh, F C H. 1987. Test of the first-on, first-in pollination hypothesis in coastal Douglas-fir, Can J For Res, 17, 63–68.
Woods, J H, and Heaman, J C. 1989. Effects of different inbreeding levels on filled seed production in Douglas-fir. Can J For Res, 19, 54–59.
Wright, S. 1921. Systems of mating. II. The effects of inbreeding on the genetic composition of a population. Genetics, 6, 124–143.
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
El-Kassaby, Y., Davidson, R. Impact of pollination environment manipulation on the apparent outcrossing rate in a Douglas-fir seed orchard. Heredity 66, 55–59 (1991). https://doi.org/10.1038/hdy.1991.7
Received:
Issue Date:
DOI: https://doi.org/10.1038/hdy.1991.7
Keywords
This article is cited by
-
SNP-based analysis reveals unexpected features of genetic diversity, parental contributions and pollen contamination in a white spruce breeding program
Scientific Reports (2021)
-
Improved genetic distance-based spatial deployment can effectively minimize inbreeding in seed orchard
Forest Ecosystems (2020)
-
Temporal quantification of mating system parameters in a coastal Douglas-fir seed orchard under manipulated pollination environment
Scientific Reports (2018)
-
High-density miniaturized seed orchards of Douglas-fir
New Forests (2015)
-
Cyclic pollen production in Cedrus deodara
Sexual Plant Reproduction (2009)