Additive genetic variation for growth and form in a Eucalyptus pellita breeding population in Colombia

Abstract

Eucalyptus pellita is one of the most important species in the warm wet tropics, due to its fast growth and form, a high wood density and higher tolerance than other eucalypt species against tropical diseases. In Colombia the species has been successfully established mainly along the Piedemonte and savanna planes of the Orinoquia plateau. The study reports a genetic analysis for growth and form from a four year old progeny/provenance trial which includes material derived from New Guinea and Australian sources. This collection provides the core breeding population for the ongoing genetic improvement program for this species in Colombia. The results confirm the general superiority of Papua and Irian-Jaya provenances from New-Guinea (PNG/IJ) provenances, relative to Australian provenances, for both growth and form. However, the heritability estimates, based only on PNG/IJ families, were low for all traits, ranging between 0.05 and 0.10. This low genetic variation highlights the need to enlarge as much as possible the genetic basis of the E. pellita in Colombia. Given the modest levels of genetic variance and heritability, and the clear inferiority of the other Australian provenances, the scope for genetic improvement from selection within the trial is modest, at around 10-15% for growth and about 10% in stem straightness, relative to the commercial seedlots of PNG/IJ origin, available in the country. A spatial analysis which assumed an autocorrelation structure (AR) between residuals was fitted to the data. The AR correlation estimates were null for form but for growth they changed from a slight positive value at age one (significant only for diameter) to a moderately negative (and significant) correlation at age two and older for both height and diameter. This result suggests the onset of competition might have started already at the early age of two years.