Heritability and Gain for Early Height Growth and Foliage Retention

Open-pollinated seeds were collected and kept identified by mother tree from 64 natural stands of eastern cottonwood (Populus deltoides Bartr. ex Marsh. var. deltoides) in the southeastern United States. Containerized rooted cuttings from the seedlings were planted in clonal trials at four sites: North Carolina, Florida, Alabama, and Missouri. Heights and late-season defoliation scores were measured at age one through three. Broad-sense heritabilities were 0.28 for thirdyear height and 0.38 for percent defoliation in October. The genetic covariance, total genetic correlation, and coefficient of genetic prediction were all negative, indicating that height increases as defoliation declines. Gains of 14-percent in height and 19-percent in foliage retention (reduced defoliation) were estimated from direct selection for clone performance over all locations. Ten-percent gains could be accomplished from indirect selection. Examination of ranked clone means indicated that selection should be based on both traits at the same time. Clone-by-test-location interactions were significant for both traits, indicating that increased gains might be accomplished by selection of site-specific clones. The same clones were seldom found in the top five clones at different test locations.

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Author(s): Jonathan P. Jeffreys, Samuel B. Land, Jr.

Publication: Tree Improvement and Genetics - Southern Forest Tree Improvement Conference - 2005