Inheritance of foliar stable carbon isotope discrimination and third-year height in Pinus taeda clones on contrasting sites in Florida and Georgia

Quantifying foliar stable carbon isotope discrimination (Delta) is a powerful approach for understanding genetic variation in gas exchange traits in large populations. The genetic architecture of Delta and third-year height is described for more than 1,000 clones of Pinus taeda tested on two contrasting sites. (h) over cap (2) for Delta was 0.14 (+/- 0.03), 0.20 (+/- 0.07), and 0.09 (+/- 0.04) at Florida, Georgia, and across sites, respectively. (H) over cap (2) for stable carbon isotope discrimination ranged from 0.25 (+/- 0.03) at the Florida site to 0.33 (+/- 0.03) at the Georgia site, while the across-site estimate of (H) over cap (2) was 0.19 (+/- 0.02). For third-year height, (h) over cap (2) ranged from 0.13 (+/- 0.05) at the Georgia site to 0.20 (+/- 0.06) at the Florida site with an across-site estimate of 0.09 (+/- 0.05). Broad-sense heritability estimates for third-year height were 0.23 (+/- 0.03), 0.28 (+/- 0.03), and 0.13 (+/- 0.02) at the Florida site, Georgia site, and across sites, respectively. Type B total genetic correlation for Delta was 0.70 +/- 0.06, indicating that clonal rankings were relatively stable across sites, while for third-year height, rankings of clones were more unstable across the two trials (r) over cap (BTG) 0.55 +/- 0.08. Thirdyear height and Delta were negatively correlated at the parental (r) over cap (ADD) = -0.42 +/- 0.33, full-sib family (r) over cap (FS) = -0.54 +/- 0.25, and clonal (r) over cap (TG) = -0.30 +/- 0.11 levels, suggesting that genetic variation for Delta in P. taeda may be a result of differences in photosynthetic capacity. We conclude that Delta may be a useful selection trait to improve water-use efficiency and for guiding deployment decisions in P. taeda.