Domestication of Radiata Pine by Rowland Burdon William Libby & Alan Brown

Author:Rowland Burdon, William Libby & Alan Brown
Language: eng
Format: epub
Publisher: Springer International Publishing, Cham

5.5.4.2 Within-Population Variation

Observed variation in putatively adaptive traits among the samples from different sites with contrasting ecological conditions within each natural population was, as of 1983, generally minor in the various provenance-trial environments in New Zealand and Australia. That was particularly surprising in the case of the samples from the large Monterey population, where there are major among-site differences in soil type, elevation, fog-days, maximum and minimum temperatures, aspect, and distance from salt-laden winds. Accepting this early evidence, the FRI breeders’ main interest continued to centre upon general tree-to-tree variation in several growth-and-form traits, their coefficients of variation (standard deviations divided by means), narrow-sense (additive) heritabilities, and genetic correlations among traits.

Analyses of data, by trait and by population sample, from the two large Genetic Survey trials provided support for the following findings from small earlier trials, namely that traits of interest differ widely in both coefficients of variation (CVs) and narrow-sense heritabilities (Burdon 1992) (Table 5.5). Growth traits, especially bole diameters at standard “breast height” (1.4 m), tended to show high CVs (often 15–20%) but fairly low heritabilities (typically ~0.2). In contrast, wood density showed a much lower CV (~8%) but much higher heritabilities (~0.5–0.7). Internode length (or its approximate inverse, frequency of branch clusters) proved not only unusually variable (CV ~20–30%), but also strongly heritable (~0.5) if measured accurately. Stem straightness, with indeterminate CV, showed lowish observed heritability (0.1–0.3) partly because of the need for visual ratings. Heritability of forking, which can be highly dependent on presence or absence of leader-damaging agents such as brush-tailed possums or diplodia dieback, was estimated as very low (0.05–0.1). These different estimates were generally consistent for each trait analysed across all native population samples, land-race samples, and even across estimates from hierarchies of plus-tree offspring (except where intensive selection had already occurred for branch-cluster frequency). As well as exhibiting low heritabilities, even within sites, bole diameter was later shown to show relatively high genotype-by-environment interactions and non-additive gene effects (Sect. 6.​7.​2.​3). Of largely academic and taxonomic interest, cone traits were very variable among trees and evidently highly heritable (Burdon 1992).Table 5.5General importance and indicative information on variability and inheritance of selected individual traits in radiata, as basically known by 1983 but often confirmed later (Mainly after Burdon 2001)

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