Effects of site and intensive culture on family differences in early growth and rust incidence of loblolly and slash pine

Lopez Upton, J.; White, T.L.; Huber, D.A.

Silvae Genetica 48(6): 284-293


ISSN/ISBN: 0037-5349
Accession: 003428825

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Eleven field tests with two silvicultural treatments (intensive and less intensive) with open-pollinated families of improved Pinus taeda, and improved and unimproved P. elliottii were established by the Cooperative Forest Genetics Research Program in the Lower Coastal Plain of the southeastern USA. Under the intensive treatment, sites were treated with fertilizers, weed control and insecticides, at different rates among sites. Results for third-year fusiform rust (Cronartium quercuum f.sp. fusiforme) infection indicated highly consistent family rankings across sites (rB-site=0.90) and across management intensities (rB-treat=0.97). Single-site heritabilities for rust in the binary scale (hsuperscript 2B 0,1) and in the underlying scale (hsuperscript 2B und=0.29) were not affected by site nor by the increase in management intensity. For third-year height growth, family rankings were less influenced by environmental differences among treatments (rB-treat=0.87) than by differences among sites (rB-site=0.57). These early results imply that stable rankings for height may be expected as cultural intensity increases. However, a few families were more responsive to culture than others. Differences in susceptibility to fusiform rust and seedling quality caused some instability in height rankings across sites. The intensive culture had a smaller site by family interaction (higher rB-site value) than less intensive culture, meaning family ranking for height were more stable across sites for intensive culture. In the intensive treatment, additive variance was reduced by 6% and environmental error decreased by 25%. This resulted in higher heritability for the intensive treatment as compared to the non-intensive treatment (hsuperscript 2B=0.3 vs. 0.2, averaged over all three taxa and all sites). The higher heritability for height growth in the intensive management treatment implies that genetic gains from progeny testing are higher in intensive culture. Furthermore, the higher heritability in the intensive culture along with little GxE between treatments (rB-treat=0.87) implies that progeny testing with intensive culture could have advantages for operational deployment in either culture.