Germplasm resources exploration and genetic gain of Toona ciliata for timber production

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Abstract

Forest tree breeding, especially for sawn timber purposes, is an important activity to circumvent the long history of predatory wood extraction in tropical ecosystems. Toona ciliata M. Roem is one of the most important species for timber production and has increasingly been planted worldwide in tropical and subtropical regions. Despite its high timber value and ecological importance, there is little scientific knowledge about this species, such as its genetic variability and genetic breeding program structure. In this study we aimed to infer the structure of genetic variance in a population of Australian red cedar (Toona ciliata), rationalising selection for breeding populations using 70 progenies of T. ciliata from 13 provenances sampled on the east coast of Australia. Individual trees were phenotyped at four ages after planting, and the data of wood volume was adjusted with mixed linear models for subsequent estimation of genetic parameters. The results of the joint analyses of wood volume showed a medium–high degree of variance among T. ciliata provenances, with (Qst) value of 0.26. The moderate narrow-sense individual heritability (ha2) was estimated to range from 0.12–0.45. As the experiment progressed, there was a notable reduction in the variances between the provenances and progenies, along with an increase in residual variance with age. In this population, the total effective population size (Ne) was estimated to be 216. The significant genetic variability observed across different provenances and progenies introduced from Australia highlights the potential for selecting individuals with higher productivity for clonal trials.

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