Nanism and Fusiform-Rust Resistance in Slash × Shortleaf Pine Hybrids

Abstract In a 4-yr-old planting, 12.5 percent of slash × shortleaf pine hybrids were dwarfs but only 2.5 percent of the slash pine half-sibs were dwarfs. Nanism among the hybrids was affected by the geographic source of shortleaf pollen, but there was no apparent geographic pattern. Evidenceis presented that nanism is a consequence of the hybridization of alien genomes. Hybrids between nonselected slash and shortleaf pines had outstanding fusiform-rust resistance, but they did not grow or survive as well as slash pine. Certain combinations of slash pine seed parent and shortleafpollen source were, however, superior in survival, growth, and rust resistance to the best slash pine progenies. Forest Sci. 17:274-278.