Southern Research Station

Title: On the origin of fusiform rust resistance in loblolly pine

Author: Schmidtling, R.C.; Nelson, C.D.; Kubisiak, T.L.

Date: 2005

Source: In: Proceedings of 28^th Southern Forest Tree Improvement Conference

Description: Studies of geographic variation in loblolly pine have shown that seed sources from the western (generally west of the Mississippi River) and the northeastern part of the natural distribution are relatively resistant to fusiform rust disease, while those from elsewhere are more susceptible. The greatest problem with rust infection, on the other hand, is in the center of the distribution, exactly where the frequency of resistant genotypes appears to be lowest. One might expect that the frequency of resistant genotypes would be higher, where the disease is more prevalent, due to natural selection. It has been proposed that (1) fusiform rust resistance in loblolly pine in the west originates from hybridization with shortleaf pine. It is well known that shortleaf pine is relatively resistant to fusiform rust, and it is also known that natural hybrids between the two species exist, and they seem to be more common in the west. In the northeast, it has been proposed that (2) hybridization with pond pine is the source of resistance to fusiform rust. Once again, natural hybridization between loblolly and pond pine is known to exist in the northeast, but not much is known about the relative resistance of pond pine to fusiform rust. Allozyme and cortical monoterpene data were used to evaluate these hypotheses and the results suggest that hybridization is not the primary source of fusiform rust resistance either in the west or northeast.

Keywords: Pinus taeda, Cronartium quercuum f. sp. fusiforme, fusiform rust, disease resistance, evolution, hybridization, Pinus echinata, Pinus serotina

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Citation

Schmidtling, R.C.; Nelson, C.D.; Kubisiak, T.L.  2005.  On the origin of fusiform rust resistance in loblolly pine.   In: Proceedings of 28^th Southern Forest Tree Improvement Conference.