"Optimum number of tested clones in seed orchards “ Iceland, Aug 28, 2003

1. "Optimum number of tested clones in seed orchards “Iceland, Aug 28, 2003 Dag Lindgren Department of Forest Genetics and Plant PhysiologySwedish University of Agricultural SciencesS-901 83 Umeå, Sweden

2. Reservations Clone number is an easy and managable concept, but this concept leads to non-optimal seed orchards. A more relevant formulation is to what degree each clone should be represented (unequal proportion deployment). Do not expect the definite answer whydiversity is needed, it will not be a main focus now.

3. How many clones…? • One of the first and most evident questions • A “key” question • Easy to adapt to the answer • Used for control, certification and monitoring

5. Literature on number of clones in seed orchards • Two previous studies has the agenda in the title: Lindgren-D 1974. Aspects of suitable number of clones in a seed orchard (proceedings); Hattemer-HH et al. 1982. Klonanzahl forstlicher Samenplantagen und genetische Vielfalt (in German). • Few citations to these studies (mostly self-citations), indicates no-one searched the literature on the issue. • I have not found a quantitative in depth discussions in a journal paper. Surprising and a bit upsetting, considering the practical significance! • So, I decided to make a new study Xmas 2002.

6. Clone number, statistics for 255 conifer seed orchards (source: Kang et al 2001 New Forest)

7. Number of clones in pine seed orchards in south US Source: McKeand et al. 2003 • Rough average • 24 clones in lob SO • 42 clones in slash SO • 6 with only 5-10 clones

8. First seed orchards • For early seed orchards with untested clones, many clones may be right. • The selected plus trees differ little in expected breeding value. • Its easier to get support for selecting plus trees and testing clones if they are in seed orchards. Thus many clones in seed orchards was a way to get tree breeding financed. • Material for grafting may sometimes be limiting. More plus trees means more material. • Seed orchards functioned as clonal archives. Thus, there has not been important reasons to argue for low numbers until recently.

9. Arguments for diversity • Genetic diversity in is likely to favour biological production: • One genotype demands the same things at the same time, several use the site resources better! • In a mix another genotype may take over the ecological space left by a failed one. • A disease spreads faster in a uniform crop. • This expectation has generally been confirmed by a number of experiments with different agricultural crops

10. Public relations, green certification etc. has an evident market value, and staff is more happy if operations are sustainable and in reasonable harmony with environment. • From this point of view it is a large advantage if the situation appears to be monitored and controlled. • Calculating Status number (=gene diversity = group coancestry) contributes to filling that function.

11. Some clone considerations… • Evolutionary potential for an individual planted forest stand should not be seen as a consideration (it must be based on national considerations).

12. Allele richness has a value only if it can save the stand, alleles in a frequency below 15% cannot save the stand, thus clonal number > 4. • Similarity with natural conditions could be an argument. Clonal numbers 10 – 25 may best mimic the natural half sib groups around seed trees. • Non-overlapping flowering can be a problem if few clones, > 4.

13. Too much diversity in plantations?! Most crop- and many forest managers do not like diversity, • Uniform trees = better economy, more valuable crop, simpler management; • Genetic superiority of the best clones is much larger than the likely loss in biomass production by uniformity; • Frequently occurring demand for diversity in intensively managed forests is – in my opinion - unreasonable expensive in lost future gain; • Most of the possible quantitative benefit with diversity is obtained by five genotypes.

14. Few clones = high gain G = genetic gain i = selection intensity r = correlation between measured “height at 6 years at some test environments” and goal “value for forestry on future environments where the seed orchard crop will be used” A = variation in desired goal character (CV additive) if r and A are given, G depends only on i. The fewer clones, the higher i and the higher G! Higher gain is the major argument for few clones!

15. The fewer selected, the higher the gain! May be 1 is the best??

16. Our study on optimum clone number • Objective was to predict optimum clone number for tested seed orchards by the aid of computer simulation • The tool: “SeedOrchardManager” at www.genfys.slu.se/staff/dagl

17. Model considerations • Genetic gain of seed orchard crop • Breeding value of available candidates • Gene diversity • Selfing • Fertility differences • Pollen contamination • Close neighbor pollination

18. Scenarios • Swedish Scots pine • American loblolly pine Most reasonable values. In Sweden these values are meant to be typical for Scots pine seed orchards to be established in the coming decade.

19. Scale and chosen entries G = BV related to average of candidates in “value for forestry” i = i(n,300) n clones selected from 300 tested candidates r = 0.7 for Sweden r = 0.8 for America(“older” and more uniform field trials and the “value for forestry” refers to a closer future) A = 0.125 (proportion from the total in BP)

20. Diversity measures Gene diversity can be measured as status number. Effective population size of an orchard is best described as foreseen status number of the seed orchard crop. But group coancestry is more convenient for the mathematics.

21. Group coancestry (Status number) Gives the probability for interaction between related tree, e.g. • competition for resources • complementing shortcomings • mating (inbreeding in plantations) • disease or pest “jump” to the same substrate • rise in group coancestry = loss of gene diversity compared to the wild forest. Thus a meaningful quantification of genetic diversity

22. Quantification of low diversity loss A high group coancestry, , can be assumed to cause reduced production, increased risk for calamities and more severe epidemics, but how much (Loss)? The loss is proportional to group coancestry, but what is the coefficient? I call it DivCoeff. The loss (on the same scale as gain) is Loss= DivCoeff x 

23. How large is DivCoeff?Thus how important gene diversity? • 59% of all loblolly is deployed as half sib family blocks and no problems are reported (McKeand et al. 2003)! The group coancestry in these plantations may be approximately  = 0.14 (Kang et al 2002). 5% loss is likely to observed. Thus DivCoeff < 0.35! • Many experiments and some forestry with full sib families. 10% loss at =0.25 would be observed, thus DivCoeff < 0.4! • Many experiments with monoclone plots and some clonal forestry. 10% loss at =0.5 would be observed, thus DivCoeff < 0.2! • Mixes of agricultural lines (=0.5) probably 2.5% superior to pure lines (=1), thus DivCoeff = 0.05!

24. DivCoeff • Swedish scenario DivCoeff = 0.4 • American scenario DivCoeff = 0.2 The difference is because south US gets more experience with low diversity forestry, less worries, less restrictions, shorter rotation times, less “Nature” (industry forestry replaced cotton, not old growth)

25. Gain and gene diversity are generally in conflict and must be compromised

26. Clones have different reproductive success • Clones give rise to different amounts of seed and pollen. • Is expressed by sibling coefficient, , (related to the probability that seedlings share a parent, Kang 2001) • Consequences of a high : • Less gene diversity (more relatedness) • More selfing • Value: =2 (Kang et al. 2003) =2means the probability that seeds share a parent is double as high as if all clones were equally reproductive successful

27. No to related clones • We used no related clones in the model; • A few related clones will cause negligible inbreeding depression, but reduce gene diversity rather considerable; • I suggest: it may sometimes be worth considering to have fewer clones rather than related.

28. Pollen sources • The ramet itself (part of selfing) • Close neighbours (not the same clone in the close neighbourhood) • Ramets which are not close neighbours (a share of the same clone causes some selfing) • Pollen contamination (outside)

29. Pollen contamination • Decreases gain • Increases gene diversity • Reduces selfing • Estimate: 40 % pollen (that means almost 50% of seeds) • Estimate of breeding value of aliens: 0.94 for Swedish; 0.85 for America (America more advanced, but even contamination “improved”) (average candidate =1)

30. Selfing • Pollen from the ramet itself (10% pollen). • Pollen from other ramets of the same clone (40% pollen)*(sibling coeff)/(clone number). • Effective percentage of selfing much less than self-pollination • Not the same clone in the close neighborhood (10% pollen). Neither contaminating pollen (40%). Thus no self-pollen in 50% of pollen cloud. • Compared to outcrossing, selfing pollen is less efficient (dead zygotes because of genetic load). • Reduction in seed yield (rather yield of plantable) seedlings to 0.3 for Swedish, 0.1 for America (compared to outcrossing). • Selfed seedlings reduce “forest value” 50%.

31. “Goodness” of seed orchard Goodness, B (“benefit”)= The formulas used look like this, more detailed explanations ín the workbook on my web

32. Just to put these thoughts and numbers into a worksheet… Parameters Results Seedorchardmanager at www.genfys.slu.se/staff/dagl

33. Results • Swedish scenario: optimal number 16 • American scenario: optimal number 8 Main cause for this difference: less problems with selfing and gene diversity in American scenario

34. If the entries are different? • Pollination pattern not critical. Breeding value of contaminates unimportant. Large contamination favors few clones. • Selfing important. Self-fertility favors many clones. • Wide genetic variation favors few clones • Many candidates moderately favors many clones • The value assigned to gene diversity is a very important factor, a high value favors many clones.

35. Optimum seems smooth!

36. Conclusions • Around 16 maybe optimal but I am a bit conservative and assumptions may be revised. So at the moment I suggest 20 as a good choice for a type case of Scots pine in Sweden with known breeding values. • Selfing and gene diversity may have been given too high weight and the sibling coefficient may be overestimed, leading to lower optimal numbers, users confident in such estimates may benefit from somewhat lower clonal numbers. • The math will be slightly different for unequal proportions, which I strongly do suggest. Perhaps we should talk about something like 25 clones deployed in different proportions.

37. The computer simulator is on my web You can use own parameters to answer this not easy question … Or you may want to study the formulas … Probably also this presentation is there… http://www.genfys.slu.se/staff/dagl/Breed_Home_Page/

38. Acknowledgement Darius Danusevicius was very helpful in constructing this slide show and made much of the graphics