Abstract
The sub-tropical species, Eucalyptus longirostrata (formerly E. punctata var longirostrata) and Corymbia henryi were investigated as alternative species for growth on the Zululand coastal plain in South Africa. Provenance/progeny trials were established in 2001 at two sites, namely, Nyalazi and Kwambonambi. The seed material purchased from the Commonwealth Scientific and Industrial Research Organization in Australia in 2000 included six provenances of E. longirostrata and five provenances of C. henryi. Six-year diameter at breast height measurements were completed in 2007. Individual narrow-sense heritability coefficients for diameter growth varied from 0.30 to 0.58 for both species, with heritabilities being higher at the drier Nyalazi site. Heritabilities and breeding values were calculated prior to making selections in field. A total of 143 selections were made in the E. longirostrata trials, and 113 in the C. henryi trials during 2008. Predicted gains for the next generation range from 2.8 cm (20%) to 6.1 cm (61%) increase in diameter for E. longirostrata, and 3.4 cm (23%) to 5.4 cm (49%) increase for C. henryi, depending on site and selection scenario. Provenance differences were evident in E. longirostrata at both sites; however, there were no significant differences between the C. henryi provenances of Australian origin. The top families of both species performed better than the hybrid controls at the Nyalazi site, indicating that both E. longirostrata and C. henryi are viable alternative species for successful growth on the drier sites of the Zululand coastal plain.