Coastal Douglas-fir seed orchards are located in southern, warmer climates which provide a natural inductive effect for improved flowering. Since all conifers are wind pollinated and the periods of reproductive development for indigenous stands and orchards overlap, non-orchard sources of pollen (contamination) can breed a significant number of female flowers (seed cones) in the orchard. Depending on the extent and magnitude of contamination, the Genetic Worth (weighted estimates of gamete contribution, see Woods 2005) of the seedlot will be reduced. This will lower the value of the seedlot and reduce future wood production.
Contamination levels in Douglas-fir seed orchards have been estimated in the range of 42 to 60% (Adams et al. 1997; Slavov et al. 2005) in Oregon and 16% (Wheeler and Jech 1986) in Washington states. Since 50% of a seedlot?s Genetic Worth (GW) is calculated from pollen contribution, contamination can result in a substantial reduction of the orchard?s GW. For example, 50% contamination in a an orchard parent rated at a breeding values of 20%, would reduce its seedlot?s GW to 15% with a potential loss of about 5% wood volume at harvest (or more if the contaminant seedlot results in maladapted planting stock for the orchard deployment zone).
Pollen Monitoring is the current protocol (see Woods et al. 1996) for assessing the magnitude of pollen contamination by estimating the ratio of non-orchard pollen cloud density (regional monitoring) to orchard pollen cloud density (which includes regional pollen). In the past there have been considerable errors in pollen identification, sampling and counting. This became the focus of a three year FSP project (Y051110 to Y073110). Sources of error in monitoring pollen cloud density were identified and specific changes were adopted. These new sampling procedures have been in effect for the last two years and estimates of contamination from pollen monitoring have been within 5% of those determined from the more robust DNA paternity analyses.
We now feel comfortable that pollen monitoring provides a reliable method for estimating the contribution of pollen contamination in coastal Douglas-fir seed orchards. However, we still do not know to what extent contaminant pollen will reduce progeny growth from high breeding value (BV) maritime orchard parents nor do we know if the progeny sired by contaminant pollen is adapted to the entire Douglas-fir maritime seed planning zone, especially on high elevation sites (800-900 m) where risk of late spring and early fall frosts are possible.
Currently we arbitrarily assign a neutral BV value (0%) to southern Vancouver Island regional pollen contamination. This has replaced the previous value of -15% based on the performance of southern Vancouver Island sources in provenance trials. The adjustment of the contaminant pollen breeding value was based on a trial where Saanich peninsula sources of pollen (contamination) were crossed with parents from the sub-maritime (coastal/interior transition zone) and compared to progeny from within orchard pollen sources (Stoehr et al. 1994 and 2004). After 9 years, the progeny from Saanich peninsula pollen (contamination) compared to within orchard sources of pollen, showed no significant reduction in growth or effect on adaptive traits (frost damage) in a plantation near Pemberton and on a coastal site on the Saanich peninsula. The lack of any effect of contaminant pollen on growth of progeny from these orchard parents was not surprising since the BV of this orchard was near 0%. We do not expect the same response when contaminant pollen is crossed with high breeding value (20%) parents (clones).
While the adjustment of the BV from -15% to 0% was not totally arbitrary, it was based on data that is applicable to the sub-maritime seed zone but not strictly applicable to the larger and certainly more economically important maritime seed zone. Accordingly, we are proposing to create a seri ...
Webber, Joe E., Stoehr, Michael U.. 2009. The effect of contamination on performance of progeny from coastal Douglas-fir Seed Orchards. Forest Investment Account (FIA) - Forest Science Program. Forest Investment Account Report. FIA2009MR364
Topic: FLNRORD Research Program
Keywords: Forest, Investment, Account, (FIA), British, Columbia
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