VIEW ARTICLE

Ecology and Epidemiology

Provenance and Family Variation in Response of Fraxinus americana and F. pennsylvanica to Ozone and Sulfur Dioxide. D. F. Karnosky, Forest geneticist, New York Botanical Garden Cary Arboretum, Millbrook 12545; K. C. Steiner, associate professor of Forest Genetics, Forest Resources Laboratory, The Pennsylvania State University, University Park 16802. Phytopathology 71:804-807. Accepted for publication 24 December 1980. Copyright 1981 The American Phytopathological Society. DOI: 10.1094/Phyto-71-804.

Two-year-old seedlings representing 10 provenances and 50 half-sib families of Fraxinus americana and 16 provenances and 59 half-sib families of F. pennsylvanica were exposed to 0.5 ppm ozone or 1.0 pp. sulfur dioxide (both as μg/m³) for 7.5 hr. The F. americana seedlings exposed to ozone were later reexposed to the same concentration, but for 7.5 hr on two consecutive days to increase the injury level so differences in pollutant tolerance could be detected. Differences in severity of foliar injury among families were significant for both species and both pollutants and accounted for 16–49% of the total variation. Variation among provenances was greater than variation within provenances for response to ozone, but the reverse was true for response to sulfur dioxide. Provenance means tended to vary with geographic origin; trees from near-coastal provenances of F. americana were generally more tolerant to ozone than those from interior provenances, and trees from southern provenances of F. pennsylvanica were generally more tolerant to both ozone and sulfur dioxide than those from northern provenances. Our results suggest that both species offer considerable potential for genetic improvement in air pollution tolerance, that improvement programs should incorporate both provenance selection and family-within-provenance selection, and that selected individual trees of these two species may serve as sensitive bioindicators of ozone and sulfur dioxide.