EFFECT OF GENETIC GAIN IN DIAMETER AND WOOD DENSITY ON ADVANCED GENERATION BREEDING STRATEGY OF ACACIA MANGIUM IN INDONESIA

Breeding of Acacia mangium in Indonesia was initially focused on selection for improving growth and stem form. Changes in wood density which resulted from selection for improved growth was impacted by adverse correlation between the both traits. This study aimed to quantify genetic gain in the diameter and wood density from two A. mangium breeding generations and to use this information in developing breeding strategy to improve both traits simultaneously. Materials were obtained from 4.5-year-old trees in a progeny trial consisting of families from first (F-1) and second (F-2) generations along with infused families (F-0) as control. Genetic gain was calculated as the percent increase in diameter and wood density from F-1 and F-2 over the control. Diameter and wood density from F-1 and F-2 were higher than F-0. Genetic gains for diameter increased from 3.7% in F-1 to 7.0% in F-2. Conversely, gain for wood density decreased from 1.9% in F-1 to 0.3% in F-2. Correlations between diameter and wood density varied from weak to moderate along the stem sections. The results imply a combined approach incorporating selection for diameter and wood density in mixed-breeding generations will provide simultaneous improvement in both traits.