Four-year growth analysis and selections in a 2nd series Corymbia henryi provenance / progeny trials series

van den Berg G, Swain T-L
Publication Type
Publication Year
ICFR Bulletin 03/2017

Corymbia henryi has shown potential for good growth and pest and pathogen tolerance in the sub-tropical and warm temperate forestry areas in South Africa. To further expand the genetic base of this species, two trials comprising six provenances from Australia were established on the Zululand Coastal Plains in 2010. Four-year diameter at breast height measurements were performed in the trials, survival and basal area per hectare calculated, and Type B correlations estimated to determine genotype x environment interaction. The Type B correlation between the two sites was 0.63 which, although indicating some interaction, is not large enough to justify separate breeding populations. Genetic parameters were estimated for both single and combined sites. The narrow-sense heritabilities for family within provenance were 0.12 at the wetter Fernwood site and 0.07 at the drier Shire site. The across-site narrow-sense heritability was 0.09, and the family heritability for families nested within provenance was estimated at 0.53 for the overall population. Elite selections were made based on a selection index derived from breeding values from diameter and basal areas predicted from the combined-site analysis. The selection index, in combination with a phenotypic evaluation for stem form and incidence of disease and pest damage, resulted in 30 selections from 18 families at Fernwood, and 22 selections from 16 families at Shire. The average predicted gain in Breeding Value, based on a combination of family values (basal area per hectare) and individual values (diameter) for the top 20 and 40 selections is 16.5% and 14.5%, respectively.