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Effect of Cercospora nicotianae Infection on Four Major Chemical Constituents in Cured Tobacco Leaves. J. R. Stavely, Research Plant Pathologist, Plant Science Research Division, ARS, USDA, Beltsville, Maryland 20705; J. F. Chaplin, Research Agronomist, Plant Science Research Division, ARS, USDA, Oxford, North Carolina 27565. Phytopathology 62:1392-1397. Accepted for publication 13 June 1972. DOI: 10.1094/Phyto-62-1392.

Cured tobacco leaves from field-grown plants that were heavily infected by Cercospora nicotianae averaged 18, 46, and 32% less total alkaloid, reducing sugar, and total phenol, respectively, and 6.5% more total nitrogen than noninfected leaves. Interactions involving presence or absence of disease in leaves from 10 cultivars, two stalk positions, and two curing methods were statistically analyzed for each of the four chemical constituents. Only in flue-cured cultivars, which had the highest inherent levels, were reducing sugar concentrations significantly less in diseased than in healthy leaves. Total alkaloids decreased less and reducing sugars decreased more in diseased leaves from the upper than in those from the lower stalk position. The average nitrogen concentration in infected leaves showed a significant increase only in those from the higher stalk position. Greater reductions occurred in reducing sugars and total phenols in infected flue-cured than in infected air-cured leaves. The results are discussed as they relate to leaf quality and disease physiology.

Additional keywords: Nicotiana tabacum L.