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We examined provenance variation in two Racosperma species (R. auriculiforme and R. mangium) on four test sites in Zaire. Seeds for the two species were obtained from Northern Territory and Queensland of Australia, Papua New Guinea, Indonesia, Congo and Zaire. Growth and morphological characters (height, diameter, number of stems, branch angle, stem straightness, volume and flowering), survival and wood specific gravity were measured at ages 3, 9, 15 and 21 months. Site effects were significant and significant provenance differences existed in all traits except branch angle. The rank of provenances changed across sites, indicating significant genotype × environment interactions. Correlations of field growth traits (diameter, height and volume) at different ages were positive but negatively correlated with nursery results. Clinal variation was observed, especially for survival rate. The Racosperma provenances with the greatest volume production were from Papua New Guinea. They are suited for reforestation programs in Zaire and other tropical countries sharing similar biogeoclimatic conditions. Additional genetic gains in growth and wood density could be obtained through selection and breeding of superior individuals from these provenances. |
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