Stability of juvenile wood specific gravity of loblolly pine in diverse geographic areas

The stability of wood specific gravity for 12-year-old loblolly pine (Pinustaeda L.) was evaluated for 18 open-pollinated families and four bulked seed lots representing provenances from the eastern shore of Maryland; Marion County, Florida; Gulf Hammock, Florida; and Livingston Parish, Louisiana. Wood samples were collected from seven plantings chosen to provide a north–south and east–west sample distribution essentially encompassing an area spanning the natural range of loblolly pine. There was significant genotype × environment interaction, and 4 of the 18 families were classified as unstable for specific gravity. These four families accounted for 49.5% of the genotype × environment interaction sum of squares. However, the loss in potential gain in a breeding program for specific gravity due to the presence of a significant genotype × environment interaction was estimated to be only 1%. Loblolly pine from the Florida provenances and from the widely planted Livingston Parish provenance consistently disp...