Fusiform Rust Incidence and Volume Growth in a First-Generation Backcross Population, (Shortleaf x Slash) x Slash

The lack of fusiform rust resistance has restricted slash pine planting to sites with a low rust hazard. An interspecies backcross breeding study was undertaken to investigate the applicability of transferring the rust resistance of shortleaf pine into slash pine. Rust resistance and volume growth of a first-generation backcross population were evaluated after 7 years of field growth. The population consisted of 12 backcross families formed by mating 1 of 6 elite slash pine clones to 2 of 7 shortleaf X slash pine F1 hybrids. Rust incidence was moderate (25%), but differences among slash pine parents were highly significant (range 11% to 54%). Differences among F1 parents were not significant, however, 4 of the 12 backcross families were less rusted than the slash pine controls. Differences in tree volume among slash pine parents and among F1 parents were significant, and half the backcross families were larger in mean tree volume than the slash pine controls. From this test, no conclusions about the applicability of transferring rust resistance from shortleaf to slash pine with backcross breeding can be made, although the volume growth of slash pine was recovered in several backcross families. In future breeding cycles, multiple rust inoculation tests, coupled with early selection and accelerated breeding, will be required to conclusively evaluate this breeding method. In practice, the careful integration of early testing, accelerated breeding, and DNA marker-assisted selection may alleviate many of the traditional problems of backcross breeding in forest tree species.

Download this file:

Download this file

Details

Author(s): C. Dana Nelson

Publication: Tree Improvement and Genetics - Southern Forest Tree Improvement Conference - 1991

Section: General Session: Breeding and Propagation