Steve is married to Sabine and they have three children. He is a quantitative geneticist and has mainly been working in forestry tree breeding research since 1990. He has the privilege to work many great colleagues, resulting in genetic resources which have been widely used in the industry. He is also a self-supporting priest, and sees science and religion converging on one common truth. Steve enjoys bird watching, running, hiking, vintage cars and diving amongst other interests.

Curriculum vitae 

 Steve Verryn obtained his MSc in Quantitative Genetics (Cum Laude) in 1985 (University of Pretoria), and his PhD in Quantitative Genetics (University of Pretoria) (1994). He was responsible for Gladiolus breeding at the Agricultural Research Council (previously VOPRI) from 1985 to 1988, after which he was appointed as a geneticist in a dog breeding program (focusing on hip dysplasia in German Shepherd dogs) at Roodeplaat Breeding Enterprises up until 1994. In 1994 he joined the CSIR, and with a team of about 18 tree breeders during his nearly 20 years at the CSIR. He was also acting Program Manager of up to approx.180 scientists and support staff in various Natural Resource disciplines including Forestry, between 2002 and 2004. He also occupied the vice-chair position as operational unit Fellow for the Science, Engineering and Technology leadership portfolio for Natural Resources and the Environment. 

 

Steve has served as consultant, external reviewer and examiner to various scientific bodies, companies and universities in South Africa, Tanzania, Kenya, Chile, Brazil, Australia, New Zealand, India and the United Kingdom. He has presented and co-presented courses on Tree Breeding, quantitative genetic, and data analysis in Portugal, Australia; India; Tanzania, and South Africa, with attendees from over 30 countries.  

 

Steve has presented three keynote addresses in international conferences and 6 other keynote and invited speaker addresses. He has been a guest on 11 radio and TV programs. A selection of his publications are to be found in the link below. 

 

Steve is also a self-supporting priest in the Anglican church, and has a BTh degree (UNISA). He is married to Sabine, and they have with three children. 

“I cannot conceive of a genuine scientist without that profound faith. The situation may be expressed by an image: science without religion is lame, religion without science is blind.”

Albert Einstein, ‘Science, Philosophy and Religion: A Symposium’, Albert Einstein, Ideas and Opinions, Bonanza Books, Crown Publishing Co., New York,1984, p. 46.

Literature 

Brief Journal Publication List 

Barros, E., Verryn, S. D., and Hettasch, M. H. 2002. Identification of PCR-based markers linked to wood splitting in Eucalyptus grandis Annals of Forest Science 59:675-678. 

Verryn, S. D. and Geerthsen, P. 1987. Heritabilities of a population of German Shepherd Dogs with a complex interrelationship structure. Theoretical and applied genetics 75:144-146. 

Verryn, S. D. and Geerthsen, P. 1988. Prediction of mature Values of conformation Characteristics for young German Shepherd Dogs. J.Small Animal Practice 29:589-595. 

Verryn, S. D. 1988. IOPB Chromosome Number Reports: Iridaceae Taxon 37: 

Verryn, S. D., Coertze, A., and Hancke, F. 1988. A Fragrant Gladiolus Germplasm Source. HortScience 

Ferreira, J. F., Verryn, S. D., and Rijkenberg, F. H. J. 1990. The phenotypical responses of gladiolus germplasm with different degrees of resistance to Uromyces transversalisEuphytica 49:215-221. 

Malan, F. S. and Verryn, S. D. 1996. Effect of Genotype-by-Environment Interaction on the Wood Properties and Qualities of Four-year-old Eucalyptus grandis and E. grandis Hybrids. South African Forestry Journal 176:47-53. 

Burdon, R. D., Hong, S. O., Shelbourne, C. J. A., Johnson, I. G., Butcher, T. B., Boomsma, D. B., Verryn, S. D., Cameron, J. N., and Appleton, R. 1997. International gene pool experiments in Pinus radiata: Patterns of genotype-site interaction New Zealand Journal of Forestry Science 27:101-125. 

Verryn, S. D. and Roux, C. Z. 1998. The use of a Simple Genetic Algorithm as a Tree Breeding Selection Technique. Southern African Forestry Journal 182:1-4. 

Hettasch, M. H. and Verryn, S. D. 1999. A repeatability study of trait assessment in a Pinus patula breeding programme Southern African Forestry Journal 185:38-44. 

Snedden, C. L. and Verryn, S. D. 1999. An investigation into the occurrence and nature of genotype by environment interaction in Pinus patula Southern African Forestry Journal 186: 

Verryn, S. D., Snedden, C. L., and Parfitt, R. C. 2000. Program for the deterministic modelling of genetic gains of tree breeding and seed and clone production strategies. Southern African Forestry Journal 189:3-9. 

Verryn, S. D. 2002. Harvesting genetics for productive plantations Southern African Forestry Journal 195:83-88. 

Kain, D and Verryn, S. D. 2005. Eucalypt and pine hybrid breeding and deployment in South Africa. International Forestry Review  7:61 (abstract) 

Verryn, S. D. and Eatwell, K. A. 2005. The feasibility of clone-site matching considering wood stress end-splitting: a case study of Eucalyptus grandis sawtimber in South Africa. International Forestry Review 7:171 (abstract) 

Verryn, S. D., Snedden, C. L., and Wessels, B. 2005. Consideration of wood quality traits in the prediction of Eucalyptus grandis sawtimber board recovery and veneer value in South Africa. International Forestry Review 7:174 (abstract) 

Snedden, C. L., Roux, C. Z., and Verryn, S. D. 2007. Broad and narrow sense heritabilities in a South African cloned open-pollinated Eucalyptus grandis breeding population. Southern Hemisphere Forestry Journal 69:81-90. 

Verryn, S. D. 2008. Breeding for wood quality- a perspective for the future. New-Zealand-Journal-of-Forestry-Science. 38:5-13. 

Verryn, S.D., Snedden, C.L., and Eatwell, K. 2009. A Comparison of Deterministically Predicted Genetic Gains with those Realised in E.grandis Breeding. Southern Forests: A Journal of Forest Science 71 (2):141-146. 

Verryn, S. D., C. L. Snedden, et al. (2009). “A Comparison of Deterministically Predicted Genetic Gains with those Realised in  E. grandis  Breeding.  .” Southern Forests: A Journal of Forest Science 71(2): 141-146. 

Eatwell, K. A., S. D. Verryn, et al. (2011). “A comparison of collinearity mitigation techniques used in predicting BLUP breeding values and genetic gains over generations.” Southern Hemisphere Forestry Journal 73(3&4): 8. 

Swain, D., S. D. Verryn, et al. (2013). “Genetic characterisation of a Eucalyptus nitens base breeding population in South Africa.” Southern Forests 75(3): 155. 

Swain, T. L., S. D. Verryn, et al. (2013). “A comparison of the effect of genetic improvement and seed source and seedling seed orchard variables on progeny growth in Eucalyptus nitens in South Africa.” Tree Genetics & Genomes. 

van den Berg, G. J., S. Verryn, et al. (2015). “Genetic Parameters of Interspecific Hybrids of Eucalyptus grandis and E. urophylla Seedlings and Cuttings.” Silvae Genetica 64(5-6): 291-308. 

Van den Berg, G. J., S. Verryn, et al. (2016). “Estimates of genetic parameters and genetic gains for growth traits of two Eucalyptus urophylla populations in Zululand, South Africa.” Southern Forests: A journal of Forest Science 78(3): 7. 

van den Berg, G. J., S. D. Verryn, et al. (2016). “Genetic parameters and genotype by environment interaction of Eucalyptus grandis populations used in intraspecific hybrid production in South Africa.” Southern Forests: A journal of Forest Science: 9. 

Hongwane, P., R. G. Mitchell, et al. (2016). “Growth and dynamic modulus of elasticity of Pinus patula × Pinus tecunumanii hybrids in Mpumalanga, South Africa.” Southern Forests: A journal of Forest Science December 2016: 9. 

Hongwane, P., G. Mitchell, et al. (2017). “Alternative pine hybrids and species to Pinus patula and P. radiata in South Africa and Swaziland.” Southern Forests: A journal of Forest Science: 1-10. 

Van den Berg, G. J., S. D. Verryn, et al. (2017). “Realised genetic gains and estimated genetic parameters of two Eucalyptus grandis × E. urophylla hybrid breeding strategies.” Southern Forests: A journal of Forest Science: 1-11. 

 

Books and book chapters 

Hettasch, M. H., Lunt, K. A., Pierce, B. T., Snedden, C. L., Steyn, D. J., Venter, H. M., and Verryn, S. D. 2005. Tree Breeding Short Course 

Hettasch, M. H., Snedden, C. L., Lunt, K. A., Pierce, B. T., and Verryn, S. D. 2007. Practical Data Analysis Tools for Tree Breeders Manual. Environmentek, CSIR, Pretoria, South Africa. 10-9pp. 

Hettasch, M. H., Snedden, C. L., Lunt, K. A., Pierce, B. T., and Verryn, S. D. 2003. Practical Data Analysis Tools for Tree Breeders Manual. Environmentek, CSIR, Pretoria, South Africa. 

Hettasch, M. H., Verryn, S. D., Snedden, C. L., Henry, R. J., and Henson, M. 2005. Tree Improvement Course for Managers. Manual. Envrionmentek, CSIR, Pretoria. 17-5pp. 

van Wyk, G. and Verryn, S. D. 2000. The Basic Principles of Tree Breeding in South Africa. In: South African Forestry Handbook 2000 Southern African Institute of Forestry pp 61-68 Chapter Section 3.3, ISBN 0-620-06439-0. 

Verryn, S. D. 1-22-1996. Introduction to Best Linear Prediction (BLP). CSIR, Pretoria. 98pp. 

Verryn, S. D. 1985. The heritability and correlations of conformation characteristics of German Shepherd Dogs. (Thesis) 65pp. 

Verryn, S. D. 1994. Improving on Best Linear Prediction for Tree Breeding (Thesis) 98pp. 

Verryn, S. D. 1997. Best Linear Unbiased Prediction (BLUP). CSIR, Pretoria. 12.4pp. 

Verryn, S. D., Hettasch, M. H., and Pierce, B. T. 2001. Optimising Tree Breeding Techniques Course Manual. CSIR, Pretoria. 

Verryn, S. D., Hettasch, M. H., and Pierce, B. T. 2002. Optimising Tree Breeding Strategies Course Manual. 2nd:. Environmentek, CSIR, Pretoria, South Africa. 

Verryn, S. D., Hettasch, M. H., Pierce, B. T., Snedden, C. L., and Steyn, D. J. 2000. Specialist Eucalypt Breeding Techniques Course Manual. CSIR, Pretoria. 

 

Refereed conference proceedings 

van Wyk, G., Pierce, B. T., and Verryn, S. D. 9-1-1991. Two year results from a site by clone interaction trial series of Eucalyptus grandis. IUFRO Symposium on Intensive Forestry: The Role of Eucalypts (Durban South Africa).334-344,  SAIF (ISBN 0 621 15961 8), Pretoria. 

Verryn, S. D., Roux, C. Z., and Geerthsen, P. 1995. Improvements on Best Linear Prediction for Breeding Purposes. Eucalypt Plantations: Improving Fibre Yield and Quality Proceedings papers.171-175, Hobart, Australia (ISBN 0 646 22904 4). 

Verryn, S. D., Fairbanks, D. H. K., Pierce, B. T., and Dyer, C. 1996. Understanding the deployment of various eucalypt species and hybrids on a range of sites in southern Africa using fuzzy logic. Tree Improvement for sustainable tropical forestry. 2:347-350, Queensland Forestry Research Institute (ISBN 0 7242 7499 4), Caloundra, Australia. 

Verryn, S. D. and Roux, C. Z. 1996. A memory-friendly algorithmic strategy for Best Linear Prediction (BLP).Tree Improvement for sustainable tropical forestry. 1:217 Queensland Forestry Research Institute (ISBN 0 7242 7499 4), Caloundra, Australia. 

Verryn, S. D., Field, C. L., Garcia, C., and Griffin, A. R. 1997. A discussion on the relationship between heritabilities and genetic correlations and the standard errors of these parameters with a case study example over two sites in South africa and one site in Uruguay.IUFRO Conference on Silviculture and Improvement of Eucalypts. 1:43-49,  Centro Nacional de Pesquisa de Florestas, Colombo: Embrapa. 

Viljoen, T. A., Case, W. M., Verryn, S. D., and Field, C. L. 1997. Test for genotype by environment interaction in Eucalyptus saligna on 7 sites in South Africa. IUFRO Conference on Silviculture and Improvement of Eucalypts.361-367,  Centro Nacional de Pesquisa de Florestas, Colombo: EMBRAPA, Brazil. 

Hettasch, M. H. and Verryn, S. D. 2000. A repeatablity study of trait assessment in a Pinus patula breeding programme. Proceedings: Forest Genetics for the next millenium. IUFRO working party 2.08.01.136-140,  ICFR, Durban. 

Pierce, B. T. and Verryn, S. D. 2000. Five year results from a site by clone interaction trial series of Eucalyptus grandis in the summer rainfall areas of South Africa. Proceedings: Forest Genetics for the next millenium. IUFRO working party 2.08.01.186-191,  ICFR, Durban. 

Verryn, S. D. 2000. Eucalypt hybrid breeding in South Africa. In: Dungey, H. S., Dieters, M. J., and Nikles, D. G. Hybrid Breeding and Genetics of Forest Trees. pp 191-199.QFRI/CRC-SPF, Noosa, Australia. 

Snedden, C. L., Verryn, S. D., and Roux, C. Z. 2000. Broad- and narrow sense heritabilities in a cloned open pollinated Eucalyptus grandis breeding population. Forest Genetics for the Next Millenium, IUFRO Working party 2.08.01 Tropical Species Breeding and Genetic Resources, Durban, South Africa.214-220,  ICFR, Durban. 

Verryn, S. D. 2000. Eucalypt hybrid breeding in South Africa. Hybrid Breeding and Genetics of Forest Trees.191-199,  QFRI/CRC-SPF, Noosa, Australia. 

Verryn, S. D. and Snedden, C. L. 2000. Optimising the expected genetic gains of various breeding and selection strategies.Proceedings: Forest Genetics for the next millennium. IUFRO working party 2.08.01.240-243,  ICFR, Durban. 

Barros, E. and Verryn, S. D. 6-11-2001. The identification of PCR-based markers linked to wood splitting in Eucalyptus grandis. Abstracts of the WBB conference: International conference on: Wood, Breeding, Biotechnology and industrial expectations.49 INRA (9th Conifer Biotechnology working group (CBWG) and IUFRO 5.01.02 and 2.04.00, Bordeaux, France. 

Verryn, S. D. 2002. Harvesting genetics for productive plantations. In: Symposium: On creating and growing trees through innovation and technology. WoodFor 2002, Pietermaritzburg, South Africa. 

Verryn, S. D. and Hettasch, M. H. 2002. Issues in Selection and Breeding Strategies for the Modern Forestry Industry. In: Advances in Genetic Improvement of Tropical Tree Species.23-27, Yogyakarta, Indonesia. 

Anderson, H., Verryn, S. D., and Crafford J. 2002. Assessing the Financial Drivers in Eucalypt Nursery Production Systems: A Conjoint Analysis Approach.Forum for Economics and Environment.Cape Town, South Africa. 

Verryn, S. D. 2002. Harvesting genetics for productive plantations. Symposium: On creating and growing trees through innovation and technology. WoodFor, 2 July 2002, Pietermaritzburg, South Africa. 

Verryn, S. D. 10-23-2002. Genetics of Eucalypt Sawtimber. Eucalyptus Saw-Timber Symposium.5-6,  NCT, Pietermaritzburg, South Africa. 

Verryn, S. D. and Hettasch, M. H. 2002. Issues in Selection and Breeding Strategies for the Modern Forestry Industry. Proceedings: Advances in Genetic Improvement of Tropical Tree Species.35-38,  Centre for Biotechnology and Tree improvement (ISBN:976-97186-0-0), Yogyakarta, Indonesia. 

Verryn, S. D. and Snedden, C. L. 23-10-2002. Genetics of Eucalypt Sawtimber. In: Eucalyptus Saw-Timber Symposium.5-6,  NCT, Pietermaritzburg, South Africa. 

Snedden, C. L. and Verryn, S. D. 2004. A comparative study of predicted gains for selection from a cloned breeding population and the implications for deployment. In: Borralho, N. M. G, Pereira, J. S., Marque, C., Coutinho, J, Madeira, M, and Tome, M. Proceedings IUFRO Conference: Eucalypts in a changing world.137-144,  RAIZ Institutto de Investigacao da Floresta e Papel, Portugal. 

Swain, T. and Verryn, S. D. 2004. Realised gains and heritabilities of eucalyptus nitens in a South African Breeding Programme. In: Borralho, N. M. G, Madeira, M, Coutinho, J, Pereira, J. S., Tome, M., and Marques, C. Proceedings IUROF Conference: Eucalypts in a changing world.216-217,  RAIZ Instituto de Investigacao da Floresta e Papel, Portugal. 

Verryn, S.D., Snedden, C.L. and Wessels, B., 2005. Consideration of wood quality traits in the prediction of Eucalyptus grandis sawtimber board recovery and veneer value in South Africa. International Forestry Review 7[5]: 174-175.[ Session 110: World IUFRO conference, Brisbane.] 

Kain, D., Verryn, S.D.2005. Eucalypt and pine hybrid breeding and deployment in South Africa. The International Forestry Review 7[5]: 61.[ Session 104: World IUFRO conference, Brisbane.] 

Verryn, S.D., Eatwell, K.A.2005. The feasibility of clone-site matching considering wood log end splitting: a case study of Eucalyptus grandis sawtimber in South Africa.  International Forestry Review 7[5]: 171. [Session 100: World IUFRO conference, Brisbane.] 

Snedden, C. L. and Verryn, S. D. 6-23-2005. A comparative study of predicted gains for selection from a cloned breeding population and the implications for deployment.  ICFR Inaugural Forest Science Symposium.  ICFR , Pietermaritzburg. 

Eatwell, K. A., Verryn, S. D., and Roux, C. Z. 2007. Investigation of the Occurrence of Instability or Collinearity in Selections made in a Series of E. grandis Progeny Trials in South Africa. IUFRO Working Group 2.08.03 “Eucalypts and Diversity: Balancing Productivity and Sustainability” 22-26 October 2007. 

Hettasch, M. H., Roux, C. Z., and Verryn, S. D. 2007. Investigation of the Efficiency of Selection Indices in Non-Hardy-Weinberg Eucalypt Hybrid Populations. IUFRO Working Group 2.08.03 “Eucalypts and Diversity: Balancing Productivity and Sustainability” 22-26 October 2007.Durban. 

Hettasch, M. H., Verryn, S. D., and Roux, C. Z. 2007. Investigation of the Efficiency of Selection Indices in Non-Hardy-Weinberg Eucalypt Hybrid Populations.IUFRO Working Group 2.08.03 “Eucalypts and Diversity: Balancing Productivity and Sustainability” 22-26 October 2007.Durban, South Africa. 

Hettasch, M. H., Snedden, C. L., and Verryn, S. D. 2007. The effect of inbreeding in Eucalyptus grandis. IUFRO Working Group 2.08.03 “Eucalypts and Diversity: Balancing Productivity and Sustainability” 22-26 October 2007.Durban, South Africa. 

Snedden, C. L., Verryn, S. D., Thompson, I., and Norris, C. 2007. Early Evaluation of Growth Properties and Discussion of Deployment Options of Hybrids with E.longirostrata for the South African Pulp Industry.IUFRO Working Group 2.08.03 “Eucalypts and Diversity: Balancing Productivity and Sustainability” 22-26 October 2007.94-94, Durban, South Africa. 

Verryn, S. D. Breeding for wood quality- a perspective for the future. Australasian Forest Genetics Conference — Breeding for Wood Quality.http://www.cdesign.com.au/proceedings%5Fafgc2007/index.htm Australasian Forestry Research Working Group 1 (Genetics) and the IUFRO Southern pine working group (2.02.20), Hobart, Tasmania, Australia. 

Verryn, S. D., Snedden, C. L., and Eatwell, K. A. 2007. A Comparison of Deterministically Predicted Genetic Gains with those Realised in E.grandis Breeding. IUFRO Working Group 2.08.03 “Eucalypts and Diversity: Balancing Productivity and Sustainability” 22-26 October 2007.104Durban, South Africa. 

Hohls, D.R. & Verryn, S.D.2008. Developing a national and international research community in tree breeding through a web-based information system. (Poster) Science real and relevant: 2nd CSIR Biennial Conference, CSIR International Convention Centre Pretoria, 17 & 18 November 2008. 

Verryn, S. D., 2008. Intellectual property management and commercialisation of forest genetic resources. In: IEG 40: The Science and Business of Varietal Forestry  Charleston, USA. 

 

 

Research-based technical reports 

1. Naidoo, N., Snedden, C. L., Verryn, S. D., and Pierce, B. T., 2008. Selection of the new generation Pinus patula breeding population to be established in 2008 Ref. No. CSIR/NRE/FOR/IR/2007/0093/C.  

2. Snedden, C. L., Verryn, S. D., Hettasch, M. H., Naidoo, N., and Pierce, B. T., 2008. A breeding strategy for Pinus elliottii for the Pine Breeding Platform: 2008 Ref. No. C. CSIR. 

3. Eatwell, K. A. and Verryn, S. D., 2007. East Africa Trip Report June 2007 Ref. No. CSIR/NRE/FOR/ER/2007/0107/C. pp. 1-26. Report on  trip undertaken as part of the project JNFT014 – East Africa GEI Tree Breeding study. 

4. Snedden, C. L., Hettasch, M. H., Eatwell, K. A., Venter, H. M., Verryn, S. D., and Pierce, B. T., 2007. A Pine Hybrid Breeding Strategy for the Pine Platform: 2007  Version 1:1 Ref. No. C. pp. 1-204.  

5. Snedden, C. L., Verryn, S. D., Eatwell, K. A., Hettasch, M. H., Malan, G. J. D., Pierce, B. T., and Venter, H. M., 2007. High performance Eucalyptus and interspecific hybrids for marginal lands in South and Eastern South Africa and South Eastern Australia Ref. No. CSIR/NRE/FOR/EXP/2007/0058/A. pp. 1-15. This is a large collaborative four year project between South Africa and (CSIR-country leader- and the University of Stellenbosch) and Australia (ACIAR, Australian National University, CSIRO and State Forests of New South Wales). The goal of this project is to improve rural livelihoods and environmental conditions on lands marginal for agriculture and commercial wood production in the medium rainfall zones of both the RSA and Australia by addressing the challenge and opportunity of achieving commercially-viable farm-and landscape-scale reforestation in marginal lands. Funding for the project was obtained from ACIAR (Australian Centre for International Agricultural Research) and co-funding from participating institutions and companies.  

6. Hettasch, M. H. and Verryn, S. D., 2006. The role that genetics can play in the protection and conservation of biodiversity Ref. No. CSIR/NRE/FOR/IR/2006/0024/C. CSIR, Pretoria.  

7. Snedden, C. L., Verryn, S. D., and Pierce, B. T., 2006. The development of a Pinus patula breeding strategy for Global Forest Products:2006 Ref. No. CSIR/NRE/FOR/ER/2006/0058/C.  

8. Verryn, S. D. and Hettasch, M. H., 2006. Synopsis of the Pine Platform- Global Forest Products workshop on pine tree traits of importance in the solid wood value chain. Ref. No. CSIR/NRE/FOR/ER/2006/0055/C. pp. 1-40. CSIR, Pretoria.  

9. Verryn, S. D., 2006. Framework for section 78 of the National Environment: Biodiversity Act, 2004 pp. 1-31. CSIR, Pretoria.  

10. Verryn, S. D. and Hettasch, M. H., 2005. Tree Improvement Science Plan 2005 Ref. No. ENV-P-I 2005-027. pp. 1-17. CSIR, Pretoria.  

11. Verryn, S. D., 2005. Programming and Database development Report: Phase II Ref. No. FOR-I 283.  

12. Hettasch, M. H., Verryn, S. D., and Barros, E., 2004. CSIR Forest Biotechnology Programme Business Plan Ref. No. ENV-P-I 2004-020. pp. 1-24. CSIR, Pretoria.  

13. Verryn, S. D., Hettasch, M. H., Ramgovind, S., and Turner, P., 2004. Forestry Programme Business plan Ref. No. ENV-P-I 2204-045. pp. 1-54. CSIR, Pretoria.  

14. Anderson, H., Verryn, S. D., and Crafford J, 2002. Forum for economics and environment: Bridging the economics/environment divide This paper focuses on an application of conjoint analysis within forestry economics. More specifically, it was used to determine eucalypt plant value perceptions among South African nurserymen, to assess the financial drivers of the eucalypt production system, and to attempt to quantify the trade-offs between attributes of a eucalypt nursery and the selling price of the plants.  

15. Lunt, K. A., Snedden, C. L., Steyn, D. J., and Verryn, S. D. 2002. Progress report 2002/03: Project Pulp ENV-P-C 2002-041: 

16.  Snedden, C. L., Steyn, D. J., Verryn, S. D., and du Buisson, S. 2001. Report on the rogueing and thinning of E.saligna trials to facilitate the collection of improved E.saligna seed for the F2 population. ENV-P-I 2001-014:1-84. Environmentek, Pretoria. 

17.  Verryn, S. D. and Turner, P. 2000. The prediction and selection of E.grandis solid wood: Phase one ENV-P-C 2000-019:1-142., Environmentek, Pretoria. 

18.  Verryn, S. D., Snedden, C. L., and Malan, G. J. D. 2000. The Early Expression of Splitting in E.grandis ENV-P-C 2000-085:1-19. Environmentek, Pretoria. 

19. Pierce, B. T. and Verryn, S. D. 2000. Backward selection Eucalyptus grandis seed orchard no. 3 at J.D.M. Keet for sawtimber seed production ENV-P-C 2000-093: Environmentek, Pretoria. 

20.  Verryn, S. D. and Bester, C. 2000. Safcol-CSIR research partnership in accelerated tree breeding: 1996-1999. Executive summary. ENV-P-C 2000 015:1-25. CSIR, Environmentek. 

21.  Snedden, C. L., Verryn, S. D., and Pierce, B. T. 1999. Second generation selections and genetic parameters based on 46 and 66 month data from Eucalyptus camaldulensis and E.tereticornis progeny trial 1010802EA2401 at Frankfort. ENV-P-C 99011:1-29. Environmentek, Pretoria. 

22. Field, C. L., Verryn, S. D., and Norris, C. 1998. Twelve month results of four NCT clonal showblocks established in the Natal Midlands. ENV/P/C 98069: Environmentek, Pretoria. 

23. Malan, G., Verryn, S. D., and Hettasch, M. H. 1998. Evaluation of UK support for the improvement and utilization of tropical pines: Review of experiences in South Africa ENV-P-C 98129:1-66. CSIR, Pretoria. 

24. Snedden, C. L. and Verryn, S. D. 1998. Recommendations on the rogueing and thinning of two E.saligna trials to facilitate the production of genetically improved E.saligna seed.1-77. CSIR Environmentek 

25. Verryn, S. D., Crafford J, PriceC S, and Bester, C. 1997. An economic Impact Study for Pinus patula solid wood production. ENV/P/C 97260:1-8. CSIR, Pretoria. 

26. Verryn, S. D., Field, C. L., and Hettasch, M. H. 1997. Breeding and Production Scenario Modeling for Pinus patula using a deterministic scenario tool to predict genetic gain. ENV/P/C 97257:1-32. CSIR, Pretoria. 

27. Verryn, S. D., Field, C. L., and Hettasch, M. H. 1997. Summary of the Pinus patula Breeding, Production and Research Strategy ENV/P/C 97261:1-18. CSIR, Pretoria. 

28. Malan, F. S. and Verryn, S. D. 1-7-1996.  Effect of genotype-by-environment interaction on the wood properties and qualities of four-year-old Eucalyptus grandis and  E. grandis hybrids ENV/P/R 96009: Environmentek, CSIR, Pretoria. 

29. von Maltitz G P and Verryn, S. D. 1996. Evaluation of Forestek’s impact in providing non-agricultural tree production technologies in support of resource-based rural development (evaluation of technologies deployed). FOR-I 665: 

30. von Maltitz, G. P., Dyer, C., Kruger, A. J., Verryn, S. D., and Parfitt, R. C. 1-3-1996. Pre-feasibility study of domestication of indigenous fruit trees and multipurpose trees FOR-I 00667: Environmentek, CSIR, Pretoria. 

Journal publications

Verryn, S.D., Snedden, C.L., and Eatwell, K. 2009. A Comparison of Deterministically Predicted Genetic Gains with those Realised in E.grandis Breeding. Southern Forests: A Journal of Forest Science 71 (2):141-146.

A Comparison of Deterministically Predicted Genetic Gains with those realised in E.grandis Breeding. Southern Forests: A Journal of Forest Science 71 (2): 141-146.  South Africa. Tree breeders often attempt to predict the genetic gains which are likely to be achieved through selection and breeding of new generations, using stochastic or deterministic modelling. There are many factors which may cause a discrepancy between the predicted and realised genetic gains. Often the predictions for genetic gains are based on single trait selection, whereas in reality, the breeding tends to be multi-trait in nature. The violation of Hardy-Weinberg conditions, assumptions regarding out crossing and relatedness, assumptions regarding the effect of the interaction between the environment and the genotype and numerous possible errors in the process of breeding, all could result in unexpected discrepancies between the realised and predicted genetic gains.

A series of genetic gains trials containing representatives of three generations of Eucalyptus grandis selections, are compared with the view to verifying the effectiveness of the E.grandis breeding program. Genetic gains of the F3. 

Verryn, S. D. 2008. Breeding for wood quality- a perspective for the future. New-Zealand-Journal-of-Forestry-Science. 38:5-13.

A challenge for breeders and wood quality researchers of today is to appropriately respond to a complex environment demanding more productivity, higher quality, and a quicker adaptation of their crops to rapid changes. This is mirrored in the typical modern commodity trends of the need for increasing quality, decreasing costs and of increasing rate of change of the markets, surrounding technologies and the environment. 

The result of such demands is that tree breeders are faced with a growing ‘shopping list’ of traits for which to breed, and in a shorter time period. This is a perilous situation, because, as the list of selection criteria increases, so too does the size of the breeding effort increase, or alternatively, the breeder may have to reduce the level of improvement in the traits. This problem is accentuated in the clonal situation, where the market expects all criteria to be met in a single genotype.  

In a recent study, with the selection target of only four traits, one tree met all criteria in a trial of 475. In another exercise, zero trees were found to be in the top 20% for all four selection traits in 773 trees. Further to these traits, there was a need to select for rooting ability and resistance to various diseases. This highlights the need to model and understand the impact of multi-trait selection on clonal breeding strategies. 

Future breeding developments are likely to: 1) limit selection traits to those anticipated to be required regardless of changing needs, and weight them in consideration of the associated risks of changing needs; 2. design strategies and adopt technologies which will enable more effective selection of multiple traits; and 3) adopt strategies which will allow effective response to the rapidly changing market, technological and natural environments. 

Challenges for wood specialists in response to the above scenarios may be to: 1) identify a few ‘generic’ traits, likely to robustly address a spectrum of possible needs of the future; 2) provide cost effective early screening techniques (biotechnology may compete here); and 3) develop technologies which will enable effective deployment (e.g. matching the predicted phenotype to the site).  The objective is to match the realised phenotype (as a result of genetic and environmental influences) to the processing needs. 

Snedden, C. L., Roux, C. Z., and Verryn, S. D. 2007. Broad and narrow sense heritabilities in a South African cloned open-pollinated Eucalyptus grandis breeding population. Southern Hemisphere Forestry Journal 69:81-90.

Genetic variances and heritabilities of a 66 month old, cloned Eucalyptus grandis breeding population of families, derived from open-pollinated selections, were estimated.  The genetic variance for the growth traits was largely additive genetic variance, whereas the proportion of non-additive genetic variance was notably higher for stem form and disease tolerance. A notably larger proportion of non-additive variance was observed for the growth traits and stem form among the F families.  This is probably due to the reduction in additive variance through selection for general combining ability for these traits in the previous generations.  No selection for disease took place in earlier generations and the proportion of non-additive genetic variance for this trait remains approximately the same for families of different generations. 

Kain, D and Verryn, S. D. 2005. Eucalypt and pine hybrid breeding and deployment in South Africa. International Forestry Review  7:61 (abstract)

In the diverse planted forests of South Africa, hybrids fulfil specific purposes. Historically in eucalypts, hybrids involving the favoured species Eucalyptus grandis have been deployed to pioneer marginal bio-climatic regions, in particular, dry and cold sites. Recently, there has been growing interest in hybridization as a means to improve wood properties. Several new hybrids of E. grandis under test aim to combine adaptation to marginal environments with superior pulping properties; others have been used to improve wood colour. Hybridization is increasingly being used in both eucalypts and pines to add disease resistance to species that are well regarded but susceptible on some sites. Work is underway to identify the most economic ways of breeding hybrids in South Africa. Given the large number of species and hybrids deployed, it is not economical to pursue separate breeding strategies for each of the hybrids using conventional intensive strategies developed in crop breeding. An approach under investigation is the combination of data from pure species progeny and from one or more hybrid taxa in an optimal manner using multi-species BLUP with appropriate economic weightings. This approach makes best use of the available correlated information in the various species and their hybrids, maximizing the total economic gain from breeding across the entire forest estate. 

Verryn, S. D., Snedden, C. L., and Wessels, B. 2005. Consideration of wood quality traits in the prediction of Eucalyptus grandis sawtimber board recovery and veneer value in South Africa. International Forestry Review 7:174 (abstract only)

The economic impact of 39 traits of 20 year old Eucalyptus grandis on sawntimber recovery and veneer value recovery were investigated in two mills. Predictive models were derived for the two products.

Veneer value was predominantly influenced by the DBH (Diameter at Breast Height), followed by the wood splitting score (evaluated in field 72 hours after felling) and interlocking grain. Other properties which play a lesser role in the veneer value are: Sapwood/heartwood ratio; minimum density of core; the standard deviation of radial shrinkage; stress probe values; disease score and stem straightness.

The sawmill value was also predominantly influenced by DBH and wood splitting, and brittle heart was included as a significant factor. Other traits of importance are total radial shrinkage and wood stress. Brittle heart was casual for 92% of the downgrading.

In conclusion, DBH, wood splitting and brittle heart were confirmed to be the major influencers on the value of Eucalyptus grandis solid wood products. These properties were investigated further. 

Verryn, S. D. and Eatwell, K. A. 2005. The feasibility of clone-site matching considering wood stress end-splitting: a case study of Eucalyptus grandis sawtimber in South Africa. International Forestry Review 7:171 (abstract only)

Plantation grown Eucalyptus grandis in South Africa can express a significant amount of log end splitting, which is usually attributed to ‘growth stresses’. The expression of end splitting, and tree growth have been shown to be subject to both environmental and genetic factors, and the interaction between these factors. The economic implications of alternative strategies to address this genotype-environment interaction are investigated. An equation is used to predict the total board volume of sawn timber from trees grown on a site, regarded as medium-high for both splitting and growth, using a sawmill study of 260 trees.  

The heritability of DBH was 0.405 and that for regressed splitting score was 0.366. The mean score of log end splitting can double, when comparing the splitting of four-year-old clones on high- and low-splitting sites. When comparing the highest and lowest splitting clones over 25 sites, the mean score of splitting varied by as much as 50%. The feasibility of matching low splitting clones to high splitting sites is compared to the feasibility of simply selecting for growth for deployment. 

Barros, E., Verryn, S. D., and Hettasch, M. H. 2002. Identification of PCR-based markers linked to wood splitting in Eucalyptus grandis Annals of Forest Science 59:675-678.

Wood splitting is a defect in eucalyptus which results in considerable losses when converting logs to solid wood products. Commonly in forestry, molecular markers are identified through studying pedigrees from a single cross. This limits the application of these markers to that population. Here we report the identification of putative molecular markers linked to wood splitting in an open-pollenated E.grandis population. Although the power to detect molecular markers in this population is low, the resultant markers are likely to be more robust and be transferred to the non-related populations. Bulked segregant analysis was used in the identification of markers from high and low splitting individuals that were selected by means of backward selection using Best Linear Prediction. The bulks were screened for differences using amplified fragment length polymorphic and random amplified polymorphic DNA primers. Following regression analysis one putative sequence characterized amplified region has been linked to splitting. 

Verryn, S. D. 2002. Harvesting genetics for productive plantations Southern African Forestry Journal 195:83-88.

Tree breeding has had significant impacts on the success of the South Africa forest industry. Examples are cited for tree growth rate, where for instance, a mean genetic improvement of 39% has been measured in F2 E.grandis over unimproved controls over various sites. The mean improvement of F1 over P0 was recorded as 15% in the genetic gains trials, which agrees with the realised reduction of rotation length by 10-15% in sawtimber crops. In E.grandis sawtimber, the impact of wood splitting has been reduced by approximately 29%. Similarly, substantial progress has been made in stem form, and species selection against pest and diseases. Selection of species with suitable properties for pulp yield is currently gaining momentum, with the increasing use of E.smithii, and the initiation of Project Pulp. Tree breeding will have to harness increasingly sophisticated technologies to make improvements in the traits which have already undergone some improvement, such as tree growth. This is due to the gradual fixing of the genes which are easily captured, leaving the more challenging inheritance for advanced breeding techniques.

There is a constant change in the market needs from trees (and tree breeders), as technologies change, markets change, and the environment changes. Tree breeding will continue to be a critical tool in maintaining a healthy forestry

Verryn, S. D., Snedden, C. L., and Parfitt, R. C. 2000. Program for the deterministic modelling of genetic gains of tree breeding and seed and clone production strategies. Southern African Forestry Journal 189:3-9.

A deterministic modeling algorithm was developed for the prediction of genetic gains of six breeding and 11 (seed and clone) production strategies. This algorithm can run iteratively over ranges of parameters which affect the genetic gains. These parameters are the selection intensities, number of families, family sizes, number of ramets per clone, duration of the strategy and heritability ranges. The genetic gains per year over these ranges are presented graphically by the algorithm. In assessing the graphs of some of the above parameters, it is apparent that commonly used selection intensity tables can result in an uneven transition in predicted genetic gain when moving from the finite to the infinite selection intensity table. 

Hettasch, M. H. and Verryn, S. D. 1999. A repeatability study of trait assessment in a Pinus patula breeding programme Southern African Forestry Journal 185:38-44.

A repeatability study of tree height, DBH, stem and crown form assessments was undertaken.  Trees were measured four times by two independent teams.  The repeatability of  five traits was estimated. The effect of repeatability on heritability of the traits was determined.  In order to obtain an indication of the feasibility of repeating measurements, the genetic gains were calculated for a hypothetical breeding population. The Best Linear Prediction (BLP) rankings of the four repetitions of the measurements were compared, with selection being based on volume, stem and crown.  The repeatabilities for height (0.81), DBH (0.98) and volume (0.97) were high and the heritabilities of these traits showed only small increases with repeated measurements.  Stem and crown form which were scored on a subjective scale, showed a repeatability of 0.61 and 0.62 respectively. Repeating scoring of these traits lead to bigger increases in the heritability of stem and crown  varied from 0.3% fir DBH to 1% for stem form. Only a total of 30% of the top 10 BLUP rankings of the four repetitions of the measurements corresponded. 

Verryn, S. D. and Roux, C. Z. 1998. The use of a Simple Genetic Algorithm as a Tree Breeding Selection Technique. Southern African Forestry Journal 182:1-4.

A genetic ranking procedure for breeding which is not dependant on statistical selection methods such as Best Linear Unbiased Prediction (BLUP) and Best  Linear Prediction (BLP) is described and results of tests on simulation breeding data are presented. A simple genetic algorithm (SGA) is adapted for the purposes of predicting genetic breeding values of individuals in a population. Coefficients are used to pool the sources of information (such as individual and family values). The coefficients are generated by the SGA, which selects the coefficients by means of a fitness test of the genetic gains (of the potential prediction coefficients) realised in a simulation population. This type of  SGA solution realised on average significantly greater gains than did BLP in simulation tests. The genetic gains the SGA realised in the simulation studies did not surpass the predicted gains of BLP, but BLP did not realise the predicted gains in 80 percent of the simulation cases. Instability described in classical regression literature may also be present in Best Linear Prediction (BLP) and Best Linear Unbiased Prediction (BLUP). 

Malan, F. S. and Verryn, S. D. 1996. Effect of Genotype-by-Environment Interaction on the Wood Properties and Qualities of Four-year-old Eucalyptus grandis and E. grandis Hybrids. South African Forestry Journal 176:47-53.

The effect of environment on growth-stress splitting, wood density, fibre length, shrinkage and heartwood content was studied using 31 five-year-old eucalypt clones, mostly Eucalyptus grandis and E. grandis based hybrids, grown in replicated trials at 26 sites.  an analysis of variance was carried out for each wood property to test the interaction between site and clone.  For each clone a linear regression of the individual property value on the mean of all clones for each site was computed as a further measure of clone-by-site interaction. Both analyses indicated that genotype-by-environment interaction does exist for some clones and taht it is applicable to all the wood properties considered except fibre length.  However, clones showing sensitivity to changes in the environment for a particular wood property did not necessarily show snesitivity in the case of other wood properties.  In other words, no clone could be singled out for showing sensitivity towards changes in the environment for all its wood properties. Although the trial was young at the time of sampling, the results indicated some important trends.  Information of this kind is of fundamental importance for tree breeding programmes as it would form a useful basis for correct choice of clones if GEI of significant nature and magnitude is detected. 

Eatwell, K. A., S. D. Verryn, et al. (2011). “A comparison of collinearity mitigation techniques used in predicting BLUP breeding values and genetic gains over generations.” Southern Hemisphere Forestry Journal 73(3&4): 8.Collinearity potentially has a negative impact on the prediction of genetic gains in tree breeding programs.

This study 

investigated the reliability and impact of best linear unbiased prediction (BLUP) using various collinearity mitigation 

techniques and of two computational numerical precisions on the genetic gains in breeding populations. Multiple-trait, 

multiple-trial BLUP selection scenarios were run on Eucalyptus grandis (F1, F2 and F3) and Pinus patula (F1 and F2) data, 

comparing predicted breeding values of parents (forward prediction) with those realised in progeny (backward prediction of 

parents). Numeric precision had an impact on intergenerational correlations of BLUPs of some scenarios, indicating that it 

may not always be optimal to use higher precision when there is collinearity in the data. The relative difference in genetic 

gains between techniques varied by up to 0.38 standard deviation units in the less-stable pine population. This highlights 

the potentially large impact that instability can have on the efficiency of a breeding programme. BLUP performed close to 

expected in the relatively stable (less collinear) population (eucalypt F1), and performed poorly in the other two populations. 

In the unstable pine data, some of the techniques resulted in improved intergenerational correlations coming in line with 

expected performance. This study indicates that BLUP can perform as expected and also confirms the potential problem 

of instability and consequences thereof. BLUP users should examine the nature of the population of predicted values and 

should these be outside expectation, various mitigation techniques should be explored. 

Hongwane, P., G. Mitchell, et al. (2017). “Alternative pine hybrids and species to Pinus patula and P. radiata in South Africa and Swaziland.” Southern Forests: A journal of Forest Science: 1-10.

Through the collaborative efforts of companies affiliated with the International Program for Tree Improvement and Conservation (Camcore), a number of pine hybrids have been produced over the last decade. Many of these have been planted in trials across southern Africa that broadly represent winter and summer rainfall areas, with the latter ranging from warm to cold temperate sites. The five-year survival and growth of the hybrids and other pines in 12 of these trials were compared with Pinus radiata in the winter rainfall, and P. patula in the summer rainfall, regions where these species have been planted extensively. Except for the highest altitude site, where freezing conditions are common, the survival of most hybrids and tropical pines was better than P. patula or P. radiata. This was, in part, attributed to their improved tolerance to the pitch canker fungus, Fusarium circinatum, which was present in the nursery at the time of planting. In the winter rainfall area, the P. elliottii ? P. caribaea hybrid, P. maximinoi and, surprisingly, the P. patula hybrids performed well. In the summer rainfall regions, hybrids with tropical parents such as P. caribaea, P. oocarpa and P. tecunumanii were more productive in the subtropical/warm temperate zone and, with increasing elevation, those hybrids crossed with P. patula performed relatively better. The P. patula ? P. tecunumanii hybrid, particularly when crossed with low-elevation P. tecunumanii, performed exceptionally across most sites. 

Hongwane, P., R. G. Mitchell, et al. (2016). “Growth and dynamic modulus of elasticity of Pinus patula × Pinus tecunumanii hybrids in Mpumalanga, South Africa.

Southern Forests: A journal of Forest Science December 2016: 9.Field establishment of South Africa’s most important commercial pine species, Pinus patula, is severely hampered by the pitch canker fungus, Fusarium circinatum. Importantly, hybrids between P. patula and other pine species tolerant to the pitch canker fungus, such as P. tecunumanii and P. oocarpa, have been identified as an alternative planting stock. In this study, variation in tree volume and dynamic modulus of elasticity (MOEdym) of the P. patula × P. tecunumanii (low- and high-elevation [LE and HE] ecotypes) hybrid was compared with the P. elliottii × P. caribaea hybrid, and the pure species P. tecunumanii (LE) and P. patula. The MOEdym was assessed using the Fakkop TreeSonic microsecond instrument across three sites. The results of the study showed that P. patula × P. tecunumanii LE performed significantly better than P. patula × P. tecunumanii HE for volume and MOEdym, which in turn was significantly better than P. patula. The MOEdym and tree growth decreased with an increase in elevation. There was significant taxon × site interaction for volume and MOEdym. The results of these trials suggested that P. patula × P. tecunumanii LE is a suitable alternative to P. patula in the Sabie region of Mpumalanga in South Africa on frost-free sites, in terms of the traits that were assessed. 

Swain, D., S. D. Verryn, et al. (2013). “Genetic characterisation of a Eucalyptus nitens base breeding population in South Africa.” Southern Forests 75(3): 155.

The measurement and statistical analysis of data from eight Eucalyptus nitens trials, established in the summer rainfall forestry region of South Africa during the 1980s and 1990s, have enabled the characterisation of the Institute for Commercial Forestry Research’s breeding population. Provenance testing showed that the more northerly New South Wales (Australia) Eucalyptus nitens provenances of Barren Mountain and Barrington Tops are distinctly better suited to the summer rainfall areas of South Africa than the southern New South Wales provenances and the Victorian provenance, Penny Saddle. Generally, the species was not badly affected by Coniothyrium canker. High type B genetic correlations for all site pairs, except one comparison, ranged from 0.75 to 0.99 for diameter at breast height (dbh), indicating very little or no genotype x environment interaction for dbh for the genotypes tested in this study. Narrow-sense heritability coefficients ranged from 0.01 to 0.34, indicating that the species generally exhibited sufficient breeding opportunity for improvement of diameter growth. High genetic correlations of greater than 0.90 between diameter measurements at 52 to 62 months after establishment and diameter measurements at 94 or 113 months were found, indicating that selections can be reliably made at five or six years. Predicted genetic gains were highest in the trials at Goedehoop and Arthur’s Seat, with increases in dbh of 3.07 cm (17.1%) and 3.17 cm (20.7%), respectively, at full rotation. 

Swain, T. L., S. D. Verryn, et al. (2013). “A comparison of the effect of genetic improvement and seed source and seedling seed orchard variables on progeny growth in Eucalyptus nitens in South Africa.”

Tree Genetics & Genomes.Eucalyptus nitens is an important forestry species grown for pulp and paper production in the temperate, summer rainfall regions of South Africa. A tree improvement programme has been ongoing at the Institute for Commercial Forestry Research for two decades, but genetic improvement in the species has been slow due to delayed and infrequent flowering and seed production. Three trials were established to firstly, quantify the gains that have been made in the first generation of improvement in the breeding programme; and secondly, establish whether a number of seed -source and orchard variables influence the performance of the progeny. These variables awere: the amount of flowering trees in the seed orchard, year of seed collection, seed -orchard origin and composition of seed -orchard seed bulks. Diameter at breast height and tree height were measured in the trials at between 87 and 97 months after establishment, and timber volumes and survival calculated. Improved seed -orchard bulks performed significantly better (p < 0.01) than unimproved controls in the field trials. Genetic gains ranging from 23.2 to 164.8m3ha-1 were observed over the unimproved commercial seed.  

There were significant differences (p < 0.01) in progeny growth between the levels of seed-orchard flowering, with higher levels of flowering (≥ 40%) producing substantially greater progeny growth than lower flowering levels (≤ 20%). The seed orchard had no effect on progeny growth in this trial series. This suggests that seed collected from any of the four seed orchards tested will produce trees with significant improvement in growth.  

van den Berg, G. J., S. Verryn, et al. (2015). “Genetic Parameters of Interspecific Hybrids of Eucalyptus grandis and E. urophylla Seedlings and Cuttings.”

Silvae Genetica 64(5-6): 291-308.The current E. grandis x E. urophylla hybrid breeding strategy of South Africa’s Forestry Industry is to maintain large breeding populations of both parental species in which parents are selected based on their general combining ability (GCA) estimates or predicted individual tree breeding values and are used for interspecific hybrid crosses.The hybrid material is first screened in seedling progeny trials after which superior individuals are selected and tested as clones. Although this strategy has delivered superior clones for commercial production in South Africa, it is a time consuming strategy to follow and more cost effective strategies are being investigated. In order to review the current hybrid breeding strategy, information on the genetic control of the traits of interest is needed for E. grandis x E. urophylla seedling and clonal populations. The main objectives of this study were therefore to firstly estimate genetic parameters for E. grandis x E. urophylla hybrid seedling and clonal populations; secondly to investigate the correlation between E. grandis and E. urophylla parental (GCA) or individual breeding values and their general hybridising ability (GHA); and lastly to determine the correlation between E. grandis x E. urophylla hybrid seedling ortets and their ramets.  

 

Results of our study indicated that non-additive genetic variation explained the majority of the total genetic variation in E. grandis x E. urophylla seedling and clonal populations. 

Due to the pre-eminence of non-additive variance, the pure-hybrid correlations were weak, especially for clonal populations. It would therefore seem that GCA or predicted individual breeding values are not good predictors of GHA for growth performance in the observed populations. 

 

Our study also indicated a weak coefficient of correlation between the growth performance of seedling ortets and their ramets. These results suggest that: firstly a hybrid breeding strategy to capture non-additive genetic variation should be adopted; and secondly that the first phase of screening E. grandis x E. urophylla hybrid material as seedlings should be revisited. 

Van den Berg, G. J., S. Verryn, et al. (2016). “Estimates of genetic parameters and genetic gains for growth traits of two Eucalyptus urophylla populations in Zululand, South Africa.” Southern Forests: A journal of Forest Science 78(3): 7.In South Africa, Eucalyptus urophylla is an important species due to its disease tolerance to fungal diseases such 

as Crysoporthe austroafricana and the Coniothyrium sp. cankers. It is mainly planted as a parental species in a 

hybrid combination with E. grandis. Generally, the E. grandis × E. urophylla hybrid has better disease tolerance and higher wood density than pure E. grandis. The current strategy is to maintain large breeding populations of both parental species in order to provide improved elite selections for hybrid crosses on a regular basis. With this in 

mind, two E. urophylla populations, consisting of five provenance/progeny trials, were established in the subtropical  region of Zululand. The aims of this study were, firstly, to determine the magnitude of genotype × environment interaction of E. urophylla in Zululand; secondly, to estimate genetic parameters and correlations for diameter at breast height (DBH), height and volume; and thirdly, to identify selections to advance the current breeding population as well as to hybridise with E. grandis. Results indicated that genotype × environment interaction effects would be practically negligible for growth in Zululand and therefore a single breeding population will be appropriate. 

In general, all growth traits were under low to moderate genetic control, with narrow-sense heritabilities ranging between 0.14 and 0.48 for volume. The genetic correlations between growth traits were high (0.98 and 0.99 for DBH– volume). This is an indication that DBH is a sufficient growth measure to use in E. urophylla breeding programmes. 

Best linear unbiased prediction estimates indicated that a selection scenario of 200 individuals will generate genetic gains of 44.7% over the population mean. The estimated gains for the top 50 individuals that could potentially be used as hybrid parents to cross with E. grandis was 59.8% over the population mean. 

van den Berg, G. J., S. D. Verryn, et al. (2016). “Genetic parameters and genotype by environment interaction of Eucalyptus grandis populations used in intraspecific hybrid production in South Africa.”

Southern Forests: A journal of Forest Science: 9.In South Africa, Eucalyptus grandis is an important species due to its fast growth and general suitability of its timber for a range of products. However, E. grandis is susceptible to fungal diseases such as Crysoporthe austroafricana and Coniothyrium sp. cankers in the subtropical region of Zululand and is therefore mainly planted as a parental species in a hybrid combination with E. urophylla in this region. The current strategy is to maintain large breeding populations of both parental species in order to provide improved elite selections for hybrid crosses. 

In order to develop the best interspecific hybrid breeding strategy for E. grandis, it is important to first determine estimates of genetic parameters of the pure species parents. Estimating the genotype by environment interaction (G×E) is also necessary in proposing the basis for setting up breeding populations and selecting environmentally stable genotypes. With this in mind, two E. grandis full-sib progeny trials were planted in Zululand and one in the KwaZulu-Natal Midlands region. The aims of this study were firstly to determine the magnitude of G×E of E. grandis across the three sites; secondly, to estimate the genetic parameters for growth of the E. grandis parents selected for intraspecific crosses; and lastly, to identify the best parents to use for intra- and interspecific crosses in future hybrid breeding programmes. Results of our study indicated that G×E would be practically negligible for growth in Zululand and one group of elite parents can be used for hybrid crosses in this region. In general, growth traits were under low to moderate genetic control, and the variation in additive genetics enabled us to identify E. grandis parents that could be utilised for intraspecific crosses and deliver progeny with genetic gains of 28.4%. Our study also highlighted that a relatively large portion of the genetic variation was explained by dominance genetic variation and a strategy to capture this non-additive variation needs investigation. Although our study achieved the stated aims, it must be kept in mind that E. grandis is mainly used as a hybrid parent with E. urophylla in Zululand. A study to investigate whether the parents with good general combining ability values from our study are also good general combiners in interspecific hybrid combinations with E. urophylla needs to be conducted. 

 

Van den Berg, G. J., S. D. Verryn, et al. (2017). “Realised genetic gains and estimated genetic parameters of two Eucalyptus grandis × E. urophylla hybrid breeding strategies.” Southern Forests: A journal of Forest Science: 1-11.Conventionally, Eucalyptus grandis × E. urophylla (GU) hybrid material is first tested as seedlings in progeny trials

for at least four years before ortets are selected and ramets of the selected ortets are propagated to test in clonal trials. The primary constraint with this ‘conventional hybrid breeding strategy’ (CHBS) is the time required to first test the hybrid material as seedlings. In order to address this, an ‘accelerated hybrid breeding strategy’ (AHBS) was investigated to reduce the time spent on testing GU hybrid material as seedlings. However, it is of utmost importance to quantify the impact the AHBS might have on genetic gains and genetic information. With this in mind, two clonal populations have been established with genetic material that derived from the CHBS and the AHBS. The main purpose of this study was to do a comparative study between the CHBS and AHBS, firstly to quantify the genetic gains per unit time for GU hybrid clonal populations that have been derived from the CHBS and AHBS respectively, and secondly to obtain genetic parameters such as heritabilities, the ratio of dominance, clonal within family variance, and the proportion of additive and non-additive genetic variance. The results indicated that the percentage realised volume gains per year was higher for the AHBS (3.7%) than for the CHBS (1.9%) when compared with the GU commercial clone. Thus, shortening the testing time of GU seedlings had a positive impact on volume gains per year. With regard to genetic parameters, both the AHBS and CHBS clonal populations indicated that non-additive genetic variation explained the majority (88% and 71%, respectively) of the genetic variation. Due to the pre-eminence of non-additive genetic variation, the narrow-sense heritabilties for the female and male effects were negligible for both clonal populations. Overall, the majority of the non-additive genetic variation was explained by the proportion of dominance variance, and less by the clone within family effect. These results suggest that, firstly, the time spent on testing GU hybrid material as seedlings should be minimised and, secondly, a hybrid breeding strategy to capture non-additive genetic variation should be adopted. 

 

Verryn, S. D. 1994. Improving on Best Linear Prediction for Tree Breeding (Thesis) 98pp.

A multitrait, memory friendly, BLP (Best Linear Prediction) algorithm for the unbalanced case, namely Matgen5, is developed. The populations used in tree improvement usually lend themselves to a special opportunity in developing a RAM-conservative algorithm, not having known complicated relationship structures. This allows for subdivision of the matrices and separate solving on a family basis in the algorithm. ‘  

The problem of instability in the solution of BLP is raised. Alternative sollutions are examined critically, indtlding the use of means, re-defining the model, principal components regressions, and ridge regressions. Alternative strategies to obtain more stable solutions are developed for testing.  

Solving predictions by genetic algorithms (GA) requires a fitness test. GA’ s imitate the evolution or breeding process. A fitness test for selecting prediction equations is formulated by use of simulated gains. It is shown that small simulated genetic populations, for which the  

Page 8 true genetic values are known, can be utilized in ‘breeding’ prediction equations using genetic algorithmS. Simulated error can also be employed as a fitness test.  

The simulated gains and simulated error techniques can also be used for the automation of ridge regression type solutions. This technique is adapted to prediction models and a ridge prediction formula is suggested, giving rise to “simulated gains ridge prediction” (SGRP) and “simulated error ridge prediction” (SERP). SGRP and SERP, as well as a simple genetic algorithm using simulated gains as the selection criterion, are compared to BLP by calculating predictions of the different techniques on a series of randomly created genetic populations. The actual gains of the techniques are then determined. The three alternative techniques all performed ‘significantly (p=O.OOOI) better than BLP (BLP=58.0%; Simple GA=66.6%; SERP=66.9%; and SGRP=67.6% average gains). Predicted gains is the best indicator of “instability” (BLP under-performance) here. Application of the above techniques to BLUP should be investigated.  

BLP achieves the predicted gain in only 20 % of the 60 test populations of 1000 individuals each. Possible reasons for the better performance of the alternative techniques developed are discussed, including collinearity, the use of random matrices, the nature of the alternative solutions, and estimation of second moments. 

 

Verryn, S. D. 1994. Improving on Best Linear Prediction for Tree Breeding (Thesis) 98pp.

Verryn, S. D., C. L. Snedden, et al. (2009). “A Comparison of Deterministically Predicted Genetic Gains with those Realised in  E. grandis  Breeding.  .” Southern Forests: A Journal of Forest Science 71(2): 141-146.

Tree breeders often attempt to predict the genetic gains which are likely to be achieved through selection and breeding of new generations, using stochastic or deterministic modelling. There are many factors which may cause a discrepancy between the predicted and realised genetic gains. Often the predictions for genetic gains are based on single trait selection, whereas in reality, the breeding tends to be multi-trait in nature. The violation of Hardy-Weinberg conditions, assumptions regarding out crossing and relatedness, assumptions regarding the effect of the interaction between the environment and the genotype and numerous possible errors in the process of breeding, all could result in unexpected discrepancies between the realised and predicted genetic gains. A series of genetic gains trials containing representatives of three generations of  Eucalyptus grandis  selections, are compared with the view to verifying the effectiveness of the  E.grandis  breeding program. Genetic gains of the F 3  (third generation of pedigreed progeny) over the F2 generation (second generation of pedigreed progeny) were 15% for 

tree growth (volume). A comparison between F2 and P0 revealed an improvement of between 20% and 33% for growth. This exercise highlighted complexities of modelling the predicted genetic gains of assimilated genetic breeding trials. The predictions of genetic gains did deviate (in both directions) from those realised, although these deviations may be explained as functions of imperfect modelling. On average, however, the predicted genetic gains for tree volume over three generationswere 13% between generations, whereas the average realised genetic gain in the genetic gains trial was 14%. It is therefore assumed that the E. grandis breeding population is indeed performing as expected, following classical tree-breeding assumptions.