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Genetic Variation in Resistance to Canker Disease of Young American Sycamore. M. V. Coggeshall, Tree Improvement Forester, Indiana Division of Forestry, Vallonia 47281. S. B. Land, Jr., Associate Professor, Department of Forestry, and V. D. Ammon, Associate Professor, Department of Plant Pathology and Weed Science, Mississippi State University, Mississippi State 39762; D. T. Cooper, Principal Plant Geneticist, and F. I. McCracken, Principal Plant Pathologist, USDA, Forest Service, Southern Forest Experiment Station, Stoneville, MS 38776. Plant Dis. 65:140-142. Copyright 1981 American Phytopathological Society. DOI: 10.1094/PD-65-140.

Nine percent of trees in a sycamore progeny test on a Mississippi River delta site exhibited leaf scorch, dieback, and lethal cankers by age 4. This represented an increase from 5% affected trees in May to 9% affected in September of the fourth growing season. Southern seed sources were least susceptible. Disease symptoms were negligible in similar tests at three locations outside the delta. Six-month-old seedlings representing some progeny families in the field tests were inoculated with Botryodiplodia theobromae in a greenhouse. Significant genetic variation among families within sources but not among sources was obtained for disease development. Correlations between greenhouse and field results were positive but low.