<I>Botrytis Fragariae</I> Causing Gray
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Clemson University TigerPrints All Dissertations Dissertations 5-2018 Detection and Characterization of the Newly Described Species Botrytis fragariae Causing Gray Mold on Strawberries in the United States Madeline Elizabeth Dowling Clemson University, [email protected] Follow this and additional works at: https://tigerprints.clemson.edu/all_dissertations Recommended Citation Dowling, Madeline Elizabeth, "Detection and Characterization of the Newly Described Species Botrytis fragariae Causing Gray Mold on Strawberries in the United States" (2018). All Dissertations. 2155. https://tigerprints.clemson.edu/all_dissertations/2155 This Dissertation is brought to you for free and open access by the Dissertations at TigerPrints. It has been accepted for inclusion in All Dissertations by an authorized administrator of TigerPrints. For more information, please contact [email protected]. DETECTION AND CHARACTERIZATION OF THE NEWLY DESCRIBED SPECIES BOTRYTIS FRAGARIAE CAUSING GRAY MOLD ON STRAWBERRIES IN THE UNITED STATES A Dissertation Presented to the Graduate School of Clemson University In Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy Plant and Environmental Sciences by Madeline Elizabeth Dowling May 2018 Accepted by: Dr. Guido Schnabel, Committee Chair Dr. Paula Agudelo Dr. Sydney Everhart 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. ii DEDICATION I would like to dedicate this dissertation to my Lord and Savior Jesus Christ. I have seen Him fulfil so many dreams in completely unexpected ways, and I can’t wait to see what He has for me in the future. I would also like to dedicate this work to my family. To my dad who always believed in me, listened to me, loved me, coached me, and supported me throughout this process. To my mom, who has always been my greatest cheerleader and teacher, and who gave me her natural curiosity and love for science. To my brother, who convinced me to go to graduate school in the first place, spent countless hours tutoring me, and has always been my best friend. Lastly, to my grandfather, Bob Dowling, who consistently supported and encouraged me to succeed throughout my undergraduate and graduate degrees. iii ACKNOWLEDGMENTS I would first like to thank Dr. Guido Schnabel, my advisor, who has supported and encouraged all my academic endeavors, has guided me expertly through the different stages of graduate school, and has taken countless hours of his time to help me develop as a scientist. It has been my great privilege and joy to work with him. I would also like to thank my committee members Dr. Agudelo, Dr. Everhart, and Dr. Kerrigan, who have enabled me to improve as a writer, public speaker, and scientist through their mentoring and friendship. Thanks to Schnabel lab members past and present, particularly Anja Grabke, Dr. Lola Fernandez-Ortuno, and Dr. Simon Li, who first welcomed me into the lab, taught me important research skills, and inspired me to be a better grad student. Many thanks to Dr. Matthias Hahn and Dr. Sabrina Rupp for their excellent collaboration and insights. Thanks also go to the undergraduate students who have been an integral part of this research. A special thank you to our technician, Karen Bryson, who has facilitated my success with her vast research knowledge and organizational skills. I would also like to thank the strawberry growers who provided samples for this study through the PROFILE resistance monitoring program. Lastly, I would like to thank all the teachers who have been mentors and friends throughout my education and spent countless hours in the classroom, office hours, and outside office hours inspiring me to be a better scientist, writer, speaker, and person. Particularly, Dr. Michael Gray, Dr. Brian Vogt, Dr. David Boyd, Dr. Gary Guthrie, Dr. Verne Biddle, Dr. Derrick Glasco, Dr. Robert Lee, Dr. Ray St. John, Mrs. Cassie Thompson, and Mrs. Shawn MacDonald. iv TABLE OF CONTENTS Page TITLE PAGE ............................................................................................................... i ABSTRACT ................................................................................................................ ii DEDICATION ........................................................................................................... iii ACKNOWLEDGMENTS .......................................................................................... iv LIST OF TABLES .................................................................................................... vii LIST OF FIGURES .................................................................................................... ix CHAPTER I. A REVIEW OF GRAY MOLD ON STRAWBERRIES ............................. 1 Background ......................................................................................... 1 Gray mold management ...................................................................... 3 Species of Botrytis causing gray mold on strawberry ............................ 6 The fungal pathogen Botrytis cinerea .................................................. 9 The fungal pathogen Botrytis fragariae ...............................................13 Objectives of this study .......................................................................15 Literature Cited ...................................................................................19 II. CHARACTERIZATION OF BOTRYTIS CINEREA ISOLATES FROM STRAWBERRY WITH REDUCED SENSITIVITY TO POLYOXIN D ZINC SALT ..............25 Abstract ..............................................................................................25 Introduction .........................................................................................26 Materials and Methods ........................................................................28 Results ................................................................................................33 Discussion ..........................................................................................35 Literature Cited ...................................................................................46 v Table of Contents (Continued) Page III. IDENTIFICATION AND CHARACTERIZATION OF BOTRYTIS FRAGARIAE ISOLATES ON STRAWBERRY IN THE UNITED STATES......................................49 Abstract ..............................................................................................49 Introduction .........................................................................................50 Materials and Methods ........................................................................52 Results ................................................................................................56 Discussion ..........................................................................................58 Literature Cited ...................................................................................70 IV. FUNGICIDE RESISTANCE IN BOTRYTIS FRAGARIAE AND SPECIES PREVALENCE IN THE MID-ATLANTIC UNITED STATES .................................................72 Abstract ..............................................................................................72 Introduction .........................................................................................73 Materials and Methods ........................................................................74 Results ................................................................................................78 Discussion ..........................................................................................80 Literature Cited ...................................................................................45 V. CONCLUSIONS ......................................................................................96