SENSITIVITY OF NURSERY PLANTS TO FREE CHLORINE IN THE MANAGEMENT OF PLANT PATHOGENS IN IRRIGATION WATER A Thesis Presented to The Faculty of Graduate Studies of The University of Guelph by DIANE FELICIANO CAYANAN In partial fulfillment of the requirements for the degree of Master of Science July, 2008 © Diane Feliciano Cayanan, 2008 Library and Bibliotheque et 1*1 Archives Canada Archives Canada Published Heritage Direction du Branch Patrimoine de I'edition 395 Wellington Street 395, rue Wellington Ottawa ON K1A0N4 Ottawa ON K1A0N4 Canada Canada Your file Votre reference ISBN: 978-0-494-42760-6 Our file Notre reference ISBN: 978-0-494-42760-6 NOTICE: AVIS: The author has granted a non­ L'auteur a accorde une licence non exclusive exclusive license allowing Library permettant a la Bibliotheque et Archives and Archives Canada to reproduce, Canada de reproduire, publier, archiver, publish, archive, preserve, conserve, sauvegarder, conserver, transmettre au public communicate to the public by par telecommunication ou par Plntemet, prefer, telecommunication or on the Internet, distribuer et vendre des theses partout dans loan, distribute and sell theses le monde, a des fins commerciales ou autres, worldwide, for commercial or non­ sur support microforme, papier, electronique commercial purposes, in microform, et/ou autres formats. paper, electronic and/or any other formats. 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Canada ABSTRACT SENSITIVITY OF NURSERY PLANTS TO FREE CHLORINE IN THE MANAGEMENT OF PLANT PATHOGENS IN IRRIGATION WATER Diane Feliciano Cayanan Advisors: University of Guelph, 2008 Dr. Youbin Zheng Dr. Michael Dixon Recycled irrigation water risks spreading pathogens, which has prompted growers to chlorinate water, but there is no research assessing chlorine ability to kill common pathogens or the use of chlorine under nursery practices. The purpose of the present research was to (1) determine any phytotoxic responses and associated free chlorine thresholds of common nursery plants; (2) determine the free chlorine thresholds and their contact times required to kill five common pathogens; and (3) examine a free chlorine concentration in relation to safety for nursery plants and killing common pathogens at a commercial nursery. Above a certain threshold concentration, nursery plants exhibited signs of chlorine injury including necrosis and chlorosis. Results indicated that irrigation water containing free chlorine < 2.5 mg-L"1 should not adversely affect the growth or appearance of nursery plants. The free chlorine threshold and critical contact time against Phytophthora infestans, Phytophthora cactorum, Pythium aphanidermatum, Fusarium oxysporum and Rhizoctonia solani were 1, 0.3, 2, 14 and 12 mg-L"1 for 3, 6, 3, 6 and 10 min, respectively. When recycled irrigation water was treated for 5 min with 2.4 mg-L"1 of free chlorine at a commercial nursery, results suggested that chlorine could be used to prevent the spread of common pathogens without losing market value of plants. ACKNOWLEDGMENTS I would like to take this opportunity to thank my advisers, Drs. Youbin Zheng and Michael Dixon, for providing me with the opportunity to participate in this degree, as well as provide me with direction and assistance throughout the past two years. I would also like to thank Dr. Calvin Chong on my advisory committee who has also provided advice and Dr. Weizhong Liu for his technical expertise. Thanks to the remainder of the MAD lab, especially Ping Zhang and Matt Hannaberg for their technical assistance. I would also like to thank Jennifer Llewellyn and Tom Intven for their plant expertise. I would like to thank Canadale Nurseries Ltd. for their generous donation of numerous plants and the use of their facilities. Thanks to Ian Stewart and Mike Matesic from ClearTech for designing the chlorination system and their technical assistance. Also, thanks to Diana Mooij and Audra Stechshyn from the University of Guelph, and Harold Piatt and Ian MacDonald from the Crop and Livestock Research Centre Prince Edward Island for providing me with plant pathogen cultures and their assistance. I also wish to thank my family for their support, especially during the last two years since their past support has led me to where I am today. I would like to acknowledge the financial support that I received during my studies from Canada-Ontario Research and Development Program (CORD), and Flowers Canada (Ontario). Financial support was also provided by the following scholarships: University Graduate Scholarship (2006), Robb Graduate Travel Grant (2007), the Ontario Pest Management Conference Best Student Paper Award (2007), and University of Guelph Graduate Bursary (2007-2008). TABLE OF CONTENTS ACKNOWLEDGMENTS i TABLE OF CONTENTS ii LIST OF TABLES v LIST OF FIGURES vi LIST OF ABBREVIATIONS vii CHAPTER 1: GENERAL INTRODUCTION 1 1.1 The Nursery and Greenhouse Industry 1 1.2 Impact of Plant Pathogens in the Nursery and Greenhouse Industry.... 2 1.3 Plant Pathogens 3 1.3.1 Oomycetes: Phytophthora and Pythium 3 1.3.1.1 Taxonomy of Oomycetes 3 1.3.1.2 Phytophthora spp 8 1.3.1.2.1 Phytophthora ramorum 9 1.3.1.2.2 Phytophthora infestans 10 1.3.1.2.3 Phytophthora cactorum 10 1.3.1.3 Pythium spp 11 1.3.1.3.1 Pythium aphanidermatum 12 1.3.1.4 Potential Risk of Phytophthora and Pythium Pathogens in Recycled Water 13 1.3.2 Fungi: Fusarium and Rhizoctonia 19 1.3.2.1 Taxonomy of Fungi 19 1.3.2.2 Fusarium spp 20 1.3.2.2.1 Fusarium oxysporum 21 1.3.2.2.2 Potential Risk of Fusarium oxysporum in Recycled Water 23 1.3.2.3 Rhizoctonia solani 26 1.3.2.3.1 Potential Risk of Rhizoctonia solani in Recycled Water 27 1.4 Nursery and Greenhouse Water Disinfestation 30 1.5 Chlorine Chemistry 33 1.5.1 Chlorine Species 33 1.5.1.1 Free Residual Chlorine 33 1.5.1.2 Combined Residual Chlorine 36 1.5.1.3 Total Residual Chlorine 36 1.5.2 Chlorine Demand 39 1.5.3 Commonly Used Chlorine Compounds ,...39 1.5.3.1 Chlorine Gas 39 1.5.3.2 Chlorine Dioxide 40 1.5.3.3 Calcium Hypochlorite 41 ii 1.5.3.4 Sodium Hypochlorite 42 1.5.4 Chlorine Detection: Colorimeter 43 1.6 Mode of Disinfestation 43 1.7 Chlorine Phytotoxicity 46 1.8 Objectives 48 CHAPTER 2: SENSITIVITY OF FIVE CONTAINER-GROWN NURSERY SPECIES TO CHLORINE IN OVERHEAD IRRIGATION WATER 49 2.1 Introduction 49 2.2 Materials and Methods 49 2.2.1 Plant Material & Treatments 49 2.2.2 C201 Oakton Colorimeter 51 2.2.3 Samples and Measurements 52 2.2.4 Statistical Analysis 53 2.3 Results 54 2.3.1 Visual Injury 54 2.3.2 Growth 55 2.3.3 Physiological Responses 56 2.4 Discussion 64 2.5 Conclusions 67 CHAPTER 3: EFFICACY OF CHLORINE IN KILLING FIVE COMMON PLANT PATHOGENS 68 3.1 Introduction 68 3.2 Materials and Methods 70 3.2.1 Medium Preparation .....70 3.2.1.1 Rye Agar Medium 70 3.2.1.2 V8 Broth 71 3.2.1.3 Clarified V8 Agar Medium 71 3.2.1.4 Unclarified V8 Agar Medium 72 3.2.1.5 P5AR Agar Medium 72 3.2.2 Propagule Production 73 3.2.2.1 Phytophthora infestans 73 3.2.2.2 Phytophthora cactorum 74 3.2.2.3 Pythium aphanidermatum 74 3.2.2.4 Fusarium oxysporum 76 3.2.2.5 Rhizoctonia solani 77 3.2.3 Chlorinated Water 77 3.2.4 Treatments ..78 iii 3.2.5 Statistical Analysis 79 3.3 Results 79 3.4 Discussion 86 3.5 Conclusions 90 CHAPTER 4: APPLICATION OF CHLORINATION TECHNOLOGY IN A COMMERCIAL NURSERY OPERATION 92 4.1 Introduction 92 4.2 Materials and Methods 93 4.2.1 Plant Material & Treatments 93 4.2.2 Samples and Measurement 97 4.2.3 Statistical Analysis 98 4.3 Results .99 4.3.1 Visual Injury 99 4.3.2 Growth 100 4.3.3 Leaf Chlorophyll Content 104 4.3.4 Free Chlorine Input and Growing Substrate 104 4.3.5 DNAMultiscan 104 4.4 Discussion 104 4.5 Conclusion 108 CHAPTER 5: SUMMARY AND FUTURE CONSIDERATIONS 109 5.1 Summary 109 5.2 Future Considerations Ill REFERENCES 114 IV LIST OF TABLES Table 1 Taxonomy of Fungi and Oomycetes 5 Table 2 Differences between Oomycetes and Fungi 6 Table 3 Phytophthora spp. recovered from water 15 Table 4 Pythium spp. recovered from water 17 Table 5 Fusarium spp. recovered from water 25 Table 6 Rhizoctonia spp. recovered from water 29 Table 7 Summary of chlorine concentrations used to treat municipal water 32 Table 8 Summary of the free chlorine thresholds and contact times required to kill microorganisms 38 Table 9 Summary of free chlorine thresholds for plants 47 Table 10 Seventeen nursery container-grown plant species and plant sources 95 Table 11 Visual injury caused by chlorinated irrigation water on 17 nursery container-grown plant species 101 Table 12 Percent reduction of growth parameters caused by chlorinated irrigation water compared to the non-chlorinated plants on container-grown nursery plant species 102 Table 13 The growth parameters of 17 container-grown nursery plant species overhead irrigated