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POSTERS: Pathogenicity and host specificity

Investigations on host specificity within the Alternaria alternata species complex
Malini Jayawardana - Michigan State University. Linda Hanson- USDA ARS

Members of the Alternaria alternata species complex (AASC) can be found as both saprophytes and pathogens. Although a wide host range has been reported for this species complex, including hosts in different plant families such as Amaranthaceae, Solanacea, Fabaceae and Rosaceae, there still is some uncertainty about whether the same species and strains affect all these potential hosts. Therefore, this study focuses on examining the host specificity of AASC strains by inoculating AASC isolated from different hosts on a set of test plants representing various plant families. Spore suspensions of AASC isolates originally collected from sugar beet and potato were inoculated to potential host tissue, such as tomato and apple fruits, as well as leaves of potato and sugar beets to test the variation in symptom production among isolates. AASC spore suspensions were inoculated into wounds of tomato and kept in a moist chamber until lesions appeared. A similar inoculation method was performed on sugar beet and potato leaves, on both wounded and non-wounded sites. The results showed a difference in symptom production by lesion diameter for the same isolate among hosts, as well as for varieties of a particular host. Additional testing is ongoing by inoculating more isolates from different crops to various hosts. Potential host specificity in the AASC could be important for crop rotation programs in agriculture.