Host relationships of fusiform rust disease: II. Genetic variation and heritability in typical and South Florida varieties of slash pine

Nelson, C.D.; Schmidtling, R.C.; Doudrick, R.L.

Silvae Genetica 45(2-3): 149-153


ISSN/ISBN: 0037-5349
Accession: 008783491

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Seedlings of wind-pollinated families from 6 sources of slash pine (Pinus elliottii var. elliottii and var. densa) were tested for development of fusiform rust disease using 2 sources of Cronartium quercuum f. sp. fusiforme inocula. The seed source origins ranged from 24.5 degree N latitude at the southern tip of Florida (P. e. densa), to 30.25 degree N latitude, in north central Florida (P. e. elliottii). All seedlings received basidiospores of both inocula; inoculum of each source was applied to a single, separate shoot. Differences among varieties of slash pine were significant, with less pycnial sporulation present on seedlings from southern seed sources. Differences between inocula were significant within P. e. elliottii only, suggesting increased specificity for P. e. elliottii hosts and these inocula, although inocula x family-within-seed-source interactions were not significant. Heritability estimates for infection or sporulation on an individual seedling basis ranged from 0 to 0.45 within P. e. densa and from 0.20 to 0.59 within P. e. elliottii. On a family mean basis, heritability estimates were higher, ranging up to 0.58 within P. e. densa and 0.71 within P. e. elliottii. Diverse sources of reaction to C. q. fusiforme appear to be present in P. e. densa, suggesting a backcross breeding approach in which genes for reaction are introgressed into fast-growing populations of P. e. elliottii. The relatively large individual tree-based heritability estimates in P. e. elliottii should help to expedite the introgression process.