Seed source variation for growth and stem form in the exotic species Khaya senegalensis in Sri Lanka.
Khaya senegalensis is an increasingly important commercial plantation species in Australia, Sri Lanka and elsewhere. To address a problem of limited information on seed source variation from across its natural and planted range for key economic traits, two seed source trials were established in Sri Lanka in 2008. These included 3 Sri Lankan landrace and 21 natural stand sources from sub-Saharan Africa. Both trials were assessed for height and survival at age 2 years and then diameter at breast height, total height and stem form traits at age 6 years. Significant differences (P<0.01) were found between seed sources for all traits at both sites. Significant differences were also found among seed sources in one trial for within seed source variability of tree volume and other traits, with two local Sri Lankan sources showing some of the highest variabilities. Whilst analyses of data pooled across the two sites revealed significant (P<0.01) seed source by site interaction effects for most traits, such interactions will be of little practical significance for growth as correlations (r values) of seed source means across the two sites were moderate and positive, but for stem form traits correlations between the sites were low to very low and not significant. Options for future genetic improvement of the species in Sri Lanka are discussed.