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Symptom Development and Disease Severity in Nicotiana tabacum and N. repanda Caused by Peronospora tabacina. M. Reuveni, Department of Plant Pathology, University of Kentucky, Lexington 40546. W. C. Nesmith, and M. R. Siegel, Department of Plant Pathology, University of Kentucky, Lexington 40546. Plant Dis. 70:727-729. Accepted for publication 14 February 1986. Copyright 1986 The American Phytopathological Society. DOI: 10.1094/PD-70-727.

Nicotiana tabacum (cv. Ky-14) and N. repanda developed different symptoms when inoculated with Peronospora tabacina (Ky-79 isolate). On Ky-14, chlorotic lesions and sporulation developed rapidly within 67 days and plants died within 1213 days of inoculation. On N. repanda, chlorosis and leaf curling (a symptom absent in Ky-14) occurred within 1014 days of inoculation. Extensive chlorosis and leaf curling also developed on adjacent uninoculated leaves within 21 days of inoculation, indicating that the fungus was developing systemically in N. repanda. Plants did not die until 60 days after inoculation. Lesions (local and systemic) on N. repanda were capable of sporulating anytime between 7 and 60 days after inoculation. Virulence of P. tabacina to N. repanda, but not to Ky-14, was greatly affected by the host plant from which inoculum was obtained. When inoculum was harvested from Ky-14, blue mold on N. repanda was two to three times more severe than when the source of inoculum was from N. repanda. These data suggest that N. repanda could be an ideal host of P. tabacina and a significant inoculum source over a long period.