University of Nebraska - Lincoln DigitalCommons@University of Nebraska - Lincoln Theses, Dissertations, and Student Research in Agronomy and Horticulture Department Agronomy and Horticulture 8-2014 Phenotypic Diversity in Lysobacter enzymogenes in Relations to Biological Control Ya Li University of Nebraska-Lincoln Follow this and additional works at: http://digitalcommons.unl.edu/agronhortdiss Part of the Plant Pathology Commons Li, Ya, "Phenotypic Diversity in Lysobacter enzymogenes in Relations to Biological Control" (2014). Theses, Dissertations, and Student Research in Agronomy and Horticulture. 77. http://digitalcommons.unl.edu/agronhortdiss/77 This Article is brought to you for free and open access by the Agronomy and Horticulture Department at DigitalCommons@University of Nebraska - Lincoln. It has been accepted for inclusion in Theses, Dissertations, and Student Research in Agronomy and Horticulture by an authorized administrator of DigitalCommons@University of Nebraska - Lincoln. University of Nebraska - Lincoln DigitalCommons@University of Nebraska - Lincoln Theses, Dissertations, and Student Research in Agronomy and Horticulture Department Agronomy and Horticulture 2014 Phenotypic Diversity in Lysobacter enzymogenes in Relations to Biological Control Ya Li Follow this and additional works at: http://digitalcommons.unl.edu/agronhortdiss Part of the Plant Pathology Commons This Article is brought to you for free and open access by the Agronomy and Horticulture Department at DigitalCommons@University of Nebraska - Lincoln. It has been accepted for inclusion in Theses, Dissertations, and Student Research in Agronomy and Horticulture by an authorized administrator of DigitalCommons@University of Nebraska - Lincoln. Phenotypic Diversity in Lysobacter enzymogenes in Relations to Biological Control By Ya Li A THESIS Presented to the Faculty of The Graduate College at the University of Nebraska In Partial Fulfillment of Requirements For the Degree of Master of Science Major: Agronomy Under the Supervision of Professor Gary Y. Yuen Lincoln, Nebraska August, 2014 Phenotypic diversity in Lysobacter enzymogenes in Relations to Biological control Ya Li, M.S. University of Nebraska, 2014 Advisor: Gary Y. Yuen Strains of the bacterium Lysobacter enzymogenes have been isolated from various regions of the world and reported to have potential as biological control agents against plant pathogens. Previous research revealed many ecological traits and mechanisms important to biological control by L. enzymogenes. Much of the previous research, however, was conducted on individual strains with little direct comparison of different strains. In this study, L. enzymogenes strains isolated from different locations and source materials (soil, roots, leaves) were compared for biocontrol- related phenotypic traits in vitro, epiphytic and endophytic colonization of leaves, and biocontrol of Bipolaris leaf spot on tall fescue. The ability to colonize leaves endophytically by L. enzymogenes was found for the first time in this study. The trait was shown to be common to all of the strains tested, with only subtle differences among strains in endophytic colonization ability. Endophytic colonization occurred after spray application of strains to bean, cabbage, Swiss chard and tall fescue, but not green onion. All of the strains tested exhibited similar ability to produce yeast cell- degrading enzymes, β-1, 3-glucanase, and antifungal secondary metabolites. Finally, all strains tested for control of Bipolaris leaf spot inhibited development of the disease, with only slight differences in levels of disease suppression among the strains. It can be concluded from the collective results that the ability to colonize leaves endophytically, the expression biocontrol-related traits, and the potential to have biological control activity are traits that are common to L. enzymogenes strains in general regardless of their origin. i Acknowledgements I would like to give my deepest appreciation to these who helped and supported me for the completion of my research. A special gratitude I give to my advisor Dr. Gary Yuen, who makes everything possible for me. He is the one that gave me the chance to stand here, and to live and spend the most wonderful three years in Lincoln. He is also the one that taught me how to do research, and the importance to keep my mind thinking. Words are not enough to express my thanks to him. I’m also thankful to one special person in our lab, Christy Jochum, who has been so helpful and supportive in my lab and greenhouse work. She made everything easier for me to access, and created a safe, happy, and organized research environment. Others I want to give my thanks to are members of my committee, Dr. Rhae Drijber and Dr. Tamra Jackson-Ziems, who were so patient and helpful with my research and thesis. Thank you for all the advices and your support. I also want to thank the student workers in our lab, especially April Mueller, Eric Kruse, and Xiaoxue Wen, for helping me when I was as busy as a beaver. Thanks to the great staff in our department, Margaret Denning, Joann Ortiz, and Marlene Busse, for helping me with forms, preparation of the seminar, and even the very little things of my life. ii Special thanks to my friends, Jianru shi, Ying Ma, Chao Tai, Jianwen He, Can Liu, Yao Li, Jinfu Leng, and Xue Zhou. I’m lucky to have your company and support in these years. I appreciate and value the time we spent together. Lastly, I own my deepest gratitude to two individuals, my parents, Mr. Chunming Li and Mrs. Qiuping Zhang. They are always there with one hundred percent support for me, they give me faith and love, and they make me who I am. iii Table of Contents Acknowledgements ........................................................................................................................... i Table of Contents ............................................................................................................................ iii Table of Figures and Tables ............................................................................................................. v 1 Literature Review ..................................................................................................................... 1 1.1 General Introduction ........................................................................................................... 1 1.2 Biological control ............................................................................................................... 2 1.2.1 Relationship of Biological control agent with plants and other microbes ............... 2 1.2.1.1 Antagonism and Plant-mediated traits ............................................................. 5 1.2.1.2 Colonization ..................................................................................................... 6 1.2.2 Importance of Lysobacter ........................................................................................ 8 1.2.2.1 Habitats and ecosystem functions .................................................................... 9 1.2.2.2 Lysobacter spp. as biological control agents .................................................. 11 1.2.2.3 Mechanisms ................................................................................................... 14 1.2.2.4 Colonization by Lysobacter ........................................................................... 21 1.3 Essential questions ............................................................................................................ 22 2 Chapter 2 Comparison of Lysobacter enzymogenes strains for biological control related traits 29 2.1 Introduction ....................................................................................................................... 29 2.2 Materials and Methods ...................................................................................................... 30 2.2.1 Bacterial strains and growth conditions ................................................................. 30 2.2.2 Phenotypic traits for species confirmation ............................................................. 31 2.2.3 Phenotypic traits associated with biological control .............................................. 32 2.2.4 Comparison of strains for biological control effectiveness against Bipolaris sorokiniana ............................................................................................................................. 33 2.3 Results ............................................................................................................................... 36 2.3.1 Phenotypic traits ..................................................................................................... 36 iv 2.3.2 Biological control traits .......................................................................................... 36 2.3.3 Comparison of biological control effectiveness against Bipolaris sorokiniana on turfgrass 37 2.4 Discussion ......................................................................................................................... 38 2.5 Figures and Tables ............................................................................................................ 41 3 Chapter 3 Phyllosphere colonization by Lysobacter enzymogenes ........................................ 51 3.1 Introduction ....................................................................................................................... 51 3.2 Materials