Taxon and family differences in survival, cold hardiness, early growth, and rust incidence of loblolly pine, slash pine and some pine hybrids

Lopez Upton, J.; White, T.L.; Huber, D.A.

Silvae Genetica 48(6): 303-313


ISSN/ISBN: 0037-5349
Accession: 003576797

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Seven taxa, including open-pollinated families of improved P. taeda (PTA), improved (PEE) and unimproved P. elliottii (PEU) and four hybrid families, PEExPTA, PEExP. caribaea var. bahamensis (PEExPCB), PEExP. caribaea var. hondurensis (PEExPCH), and the backcross PEE to PEExPCH, were tested in eight field tests in the lower Coastal Plain of the southeastern (northern Florida and southern Georgia) USA. Each field test included 16 families per taxon and two silvicultural treatments, intensive and less intensive. The intensive treatment included fertilizer and insecticide application and weed control. Results at three years of age indicated that PTA was the best taxon, followed by PEE. PEEx(PEExPCH) and PEExPCB were less affected by cold damage and were taller than PEExPCH, and had height growth similar to the PEE families. All slashxCaribbean hybrids were more susceptible to fusiform rust (caused by Cronartium quercuum f.sp. fusiforme) than PEE. The PEExPTA hybrid was intermediate for rust incidence and height growth between the PEE and PTA parental species, but mean values were closer to PEE. Taxon ranking for height growth was not affected by cultural treatments, but differences increased in the intensive treatment. Outstanding healthy trees were detected in all hybrid taxa. Larger hybrid heritabilities (h2h) and more within hybrid family variability for height compared to within families of parental species were detected and this may be exploited by selection within hybrid families to find outstanding recombinants. If these early results are confirmed in later years, the technique of reciprocal recurrent selection does not hold much promise since it is based on operational deployment of the F1 hybrids and none of the hybrids tested here outperformed the current pure taxa being deployed (PEE and PTA). The excellent individual trees within hybrid taxa might be useful for breeding purposes in hybrid programmes that combine genes from the hybrids back with the parental PEE and PTA species in various combinations to form synthetic taxa.