Best Practice

Panmixis

  • Panmixis (or panmixia) with reference to a seed orchard means that all clones within the seed orchard have an equal chance of “mating”. The importance of panmixis for seed orchards is that if it does not occur i.e. not all or only a few clones are cross breeding (mating), then there is likely to be a significant deviation from the stated predicted gain in the material derived from the seed orchard.
  • In many countries there are strict controls on the marketing of seed as tested i.e. predicted to produce seed with stated genetic gains. Often seed suppliers are regulated and not allowed to market the seed as “tested” unless the supplier can prove that panmixis has occurred.
  • With tested Sitka seed orchards in the UK in the past, the practice was not to release seed for sale in the open market unless there was panmixis. However the  practice was ended some years ago due to funding issues and currently seed supplied from  seed orchards as tested material is no longer subject to panmixis controls. The Co-op believes this practice is unacceptable and intends to introduce a kite-mark which notifies the buyer either that panmixis has occurred or that it has not occurred but there has been a measure of flowering and coning clones so that the predicted gains can be accordingly restated.

When to use SO and when to use FS.

  • Experience to date would suggest that Seed orchard material is well placed to replace QCI on any sitka sites. Full sibling because of the way in which it is propagated by vegetative reproduction has a different root system. Nursery husbandry has dramatically improved the material over recent year. Best results are achieved when it is used on average to good sitka sites, thus allowing them to reveal their genetic characteristics earlier in the establishment phase.

How to mix FS to ensure genetic diversity.

  • With seed orchards there are normally 40 parents represented, whilst with Full sibling material we know both the mother and the father. It is thus wise to build up your forest by using a mix of Seed orchard on the poorer sitka sites and then a mix of different Full sibling families across the average and better sitka sites. The map shows one example of how this has been done. (Map: Dryfe Restocking Provenance)