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Poster: Diseases of Plants: Disease Detection & Diagnosis


Fungal Diseases of Stevia rebaudiana Grown in Eastern Tennessee
T. COLLINS (1), M. Dee (1), H. Korotkin (1), D. Hensley (1), B. Ownley (1) (1) University of Tennessee, U.S.A.

Extract of Stevia rebaudiana, a plant native to Brazil and Paraguay, is a substitute for sugar to sweeten food and drink products. In the last five years, acreage of stevia for commercial production has increased significantly in the southeastern USA. Crops produced in large acreage monoculture are more susceptible to pathogens; potentially destroying whole crops or limiting crop yields. The aim of this study was to identify fungi recovered from diseased stevia field plants grown in Eastern Tennessee. Fungi were screened for pathogenicity in detached stevia leaf assays. Isolates that caused significant necrosis on detached leaves were identified and evaluated in replicated, greenhouse plant disease assays. Pathogens with significant potential to cause disease were identified as Fusarium armeniacum, Botrytis cinerea, and Alternaria alternata. Fungal identification was based on morphological characteristics and sequence identity of the internal transcribed spacer region of 18S ribosomal DNA, and translation elongation factor 1-alpha. Nucleotide amplicons obtained with PCR, were compared with published sequences in Fusarium-ID and the National Center for Biotechnology Information. In greenhouse assays, inoculated plants exhibited necrotic leaf lesions, similar to those observed in field plants. The three fungi were re-isolated from inoculated plants and identity was re-confirmed. Early identification and management of known stevia pathogens will help reduce crop loss.