Date of Award

5-2018

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Committee Member

Dr. Guido Schnabel, Committee Chair

Committee Member

Dr. Paula Agudelo

Committee Member

Dr. Sydney Everhart

Committee Member

Dr. Julia Kerrigan

Abstract

Gray mold is one of the most devastating diseases infecting strawberries worldwide. Though Botrytis cinerea is the most common causal agent of this disease, five other species are also currently known to cause gray mold on strawberry: Botrytis pseudocinerea, Botrytis caroliniana, Amphobotrys ricini, Botrytis mali, and Botrytis fragariae. This work focuses on the newly described species B. fragariae in the Mid-Atlantic United States: its discovery, distribution, and fungicide resistance patterns. B. fragariae was originally detected in a study of Botrytis species infecting German strawberry fields. It was later detected in the United States through research on the fungicide polyoxin D. Isolates were found with reduced sensitivity to this fungicide, though polyoxin D had not been applied in the locations where reduced sensitivity was detected. This reduced sensitivity was later found to be characteristic of many isolates of B. fragariae. Further characterization of this species revealed an apparent preference for strawberry flower over fruit tissue, and a seeming absence of B. fragariae in nurseries producing strawberry transplants. When B. fragariae and B. cinerea were compared in fungicide resistance profiles and chemical class resistance profiles, both profiles were different between species. Most importantly, B. fragariae isolates did not exhibit resistance to the Succinate Dehydrogenase Inhibitor fungicides, but exhibited higher frequencies and levels of resistance to the commonly used active ingredient fludioxonil than B. cinerea. Future work is necessary to investigate B. fragariae’s genetic differences from B. cinerea, to further understand its geographic distribution, and to show the relative importance of this species to strawberry production worldwide.

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