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Early Symptomatology of Fusiform Rust on Pine Seedlings. J. E. Lundquist, Graduate research assistant, Department of Plant Pathology, University of Georgia, Athens 30602; E. S. Luttrell, professor, Department of Plant Pathology, University of Georgia, Athens 30602. Phytopathology 72:54-57. Accepted for publication 1 May 1981. Copyright 1982 The American Phytopathological Society. DOI: 10.1094/Phyto-72-54.

The first macroscopic symptom of fusiform rust, caused by Cronartium quercuum f. sp. fusiforme, on slash pine (Pinus elliottii var. elliottii) and loblolly pine (P. taeda) is red pigmentation that develops in various patterns on stems and needles. Early symptoms on seedlings grown in vermiculite-filled tubes were studied on the basis of proportion of seedlings developing stem pigment and the number of lesions developing on seedling stems and how these changed with time. Seedlings from half-sib families of both slash and loblolly pines showed a rapid rate of increase in both proportion of pigmented seedlings and numbers of stem lesions after an initial lag period. Resistant families had greater rates of increase than susceptible families. Increasing levels of inoculum resulted in larger proportions of pigmented seedlings and larger numbers of stem lesions. High inoculum densities amplified the difference between resistant and susceptible families.

Additional keywords: disease resistance, early symptoms.