Sapling and coppice biomass heritabilities and potential gains from Eucalyptus polybractea progeny trials

Abstract

Eucalyptus polybractea has been planted as a short-rotation coppice crop for bioenergy in Western Australia. Historical breeding selections were based on sapling biomass and despite a long history as a coppice crop, the genetic parameters of coppicing are unknown. Here, we assessed sapling biomass at ages 3 and 6 from three progeny trials across southern Australia. After the second sapling assessment, all trees were harvested. Coppice biomass was assessed 3.5 years later. Mortality following harvest was between 1 and 2%. Additive genetic variance for the 6-sapling estimate at one site was not significant. Sapling heritabilities were between 0.06 and 0.36 at 3 years, and 0.18 and 0.20 at 6 years. The heritability for the coppice biomass was between 0.07 and 0.17. Within-site genetic and phenotypic correlations were strong between all biomass assessments. Cross-site correlations were not different from unity. Selections based on net breeding values revealed positive gains in sapling and coppice biomass. Lower or negative gains were estimated if 3-year sapling selections were applied to the coppice assessments (−7.1% to 3.4%) with useful families culled. Positive gains were obtained if 6-year sapling selections were applied to the coppice assessment (6.4% to 9.3%) but these were lower than those obtained by applying coppice selections to the coppice assessment (8.4% to 14.8%). Removal of poor performing families and families that displayed fast sapling growth rates but under-performed as coppice will benefit potential coppice production. These results indicate that selections should be made using coppice data.

Testing New Provenances of Eucalyptus polybractea: A Eucalypt Oil Mallee Adapted to Semi-Arid Environments

“…Early plantations were established from wild-collected seed with only rudimentary levels of selection for oil yield and %cineole. By the 1990s, this had changed [8], with the realisation that the drivers of oil quality and yield per hectare, namely %cineole, concentration of oils in the leaves, and leaf biomass, were independent traits of low (growth traits) to high (oil traits) heritability and all amenable to concurrent improvement by selection and breeding [9,10]. The companies in NSW and Vic commenced tree improvement based on seed and clones from stands near their centres of operation in the 1990s: though formal provenance and family testing was not carried out, the local region of provenance is thought to perform best at both locations.…”