Original Articles

Predicted and realized genetic gain in Eucalyptus grandis breeding seedling orchard in Zimbabwe


Abstract

Results are presented of a fourth generation breeding seedling orchard of Eucalyptus grandis Hill Maiden of 30 half-sib families. Measurements at one and half and five years were available. Analysis of one and half year data showed no significant differences between the families for height, diameter at breast height, volume, and stem straightness but 5 year data showed significant differences for height, diameter, and volume but no significant differences emerged for stem straightness. Individual tree heritability (h2 b) estimates for height, dbh, volume, and stem straightness at 5 years were 0.20 ± 0.08,0.16 ± 0.19,0.12 ± 0.14, and 0.10 ± 0.09 respectively. Estimates of family heritability (h2 r) for height, diameter, and volume were moderately high (0.64 ± 0.15, 0.69 ± 0.11, 0.55 ± 0.28, and 0.30 ±0.13 respectively) but less so for stem straightness at five years. Predicted genetic gains in volume for family selection in E. grandis is 14.5% and estimates of realized genetic gains at the fourth generation level from the first generation selections in E. grandis material at 5 years is 31%. Deployment of the most productive families has the potential to increase the site-index values. These values are of high economic importance to the forestry sector in Zimbabwe.

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