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Early Results From a Site-Replicated Pecan Progeny Test

An open-pollinated progeny test of 40 pecan families of central Louisiana origin was replicated on 3 sites in southern Louisiana and Mississippi. A high degree of genetic variation in first-year height and root growth, field survival, and second-year height growth was found, with significant effects partitioned in the component for stand or local breeding population variance. The latter effect indicates a closer degree of relationship or genetic homogeneity within small breeding groups, reflecting a relatively high level of inbreeding in wild populations. Genetic homogeneity within small populations was also demonstrated by the comparatively good survival and growth of progenies of unselected trees from each selected stand, indicating that phenotypic stand selection may be as effective as individual tree selection in the first generation. Comparisons of the 3 test sites emphasized the magnitude of environmental effects on survival and growth of pecan, a site-specific species. No GXE interactions were found between the two bottomland sites, but major effects were noted on the better-drained upland site. These differences were reflected in estimates of heritability of second-year height growth, which ranged from 0.22 (narrow) and 0.57 (broad) to 0.41 (narrow) and 0.74 (broad) when calculated on the basis of bottomland-upland and bottomland-bottomland test site performance, respectively.

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Author(s): John C. Adams, Bart A. Thielges

Publication: Tree Improvement and Genetics - Central States Forest Tree Improvement Conference - 1976