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Epidemiological Studies of Downy Mildew of Oilseed Poppy

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Epidemiological Studies of Downy Mildew of Oilseed Poppy Epidemiological studies of downy mildew of oilseed poppy by Jason Barry Scott, BAgrSc(Hons) Submitted in fulfilment of the requirements for the Degree of Doctor of Philosophy University of Tasmania, Burnie, Australia December, 2003 This thesis contains no material that has been accepted for the award of any other higher degree or diploma in any University, and to the best of my knowledge contains no paraphrase of material written or published by any other person except where due reference is made in the text. Jason Barry Scott University of Tasmania Burnie, Australia December, 2003 Ill Table of Contents TABLE OF CONTENTS ...................................................................................... iv LIST OF TABLES .............................................................................................. viii LIST OF FIGURES.............................................................................................. xii LIST OF EQUATIONS...................................................................................... xvii ACKNOWLEDGMENTS ................................................................................. xviii ABSTRACT .......................................................................................................... xx 1. INTRODUCTION .......................................................................................... 1 2. LITERATURE REVIEW ............................................................................... 3 2.1. OILSEED POPPY .............................................................................................. 3 2.1.1. Botany ................................................................................................... 3 2.1.2. History and current production ............................................................. 6 2.1.3. Cultivation in Australia ......................................................................... 8 2.1.4. Major pathogens ................................................................................. 11 2.2. DOWNY MILDEW OF POPPY ........................................................................... 15 2.2.1. Symptoms ............................................................................................ 15 2.2.2. Taxonomy ........................................................................................... 17 2.2.3. Disease cycle ...................................................................................... 23 2.2.4. Climatic effects ................................................................................... 36 2.2.5. Current control ................................................................................... 59 2.3. DETECTION OF DOWNY MILDEW ................................................................... 62 2.3.1. Biological detection ............................................................................ 62 2.3.2. Molecular detection ............................................................................ 65 2.4. CHARACTERISING EPIDEMIC DEVELOPMENT .................................................. 68 2.4.1. Spatial analysis ................................................................................... 68 2.4.2. Spatial association .............................................................................. 79 2.4.3. Temporal and spatiotemporal analysis ................................................ 84 3. IDENTIFICATION OF THE DOWNY MILDEW PATHOGEN OF POPPY IN TASMANIA ....................................................................................... 89 iv 3.1. INTRODUCTION ............................................................................................ 89 3.2. MATERIALS AND METHODS .......................................................................... 91 3.2.1. Sample collection ................................................................................ 91 3.2.2. Morphological observations ................................................................ 91 3.2.3. DNA amplification .............................................................................. 92 3.2.4. DNA sequencing and phylogenetic analysis ......................................... 95 3.2.5. Primer design ...................................................................................... 97 3.3. RESULTS ....................... ·············································· ············· ................... 98 3.3.1. Morphological observations ................................................................ 98 3.3.2. Sequence analysis ............................................................................. 100 3.3.3. Phylogenetic analysis ........................................................................ 105 3.3.4. Primer Design ................................................................................... 108 3.4. DISCUSSION ............................................................................................... 109 4. EPIDEMIC DEVELOPMENT OF PERONOSPORA CRISTATA IN OILSEED POPPY .............................................................................................. 114 4.1. INTRODUCTION .......................................................................................... 114 4.2. MATERIALS AND METHODS ........................................................................ 117 4.2.1. Field trials ........................................................................................ 117 4.2.2. Temporal analysis ............................................................................. 121 4.2.3. Spatial analysis ................................................................................. 121 4.2.4. Spatiotemporal analysis .................................................................... 124 4.2.5. Spatial association ............................................................................ 125 4.3. RESULTS ··································································································· 127 4.3.1. Temporal analysis ............................................................................. 127 4.3.2. Spatial analysis ................................................................................. 129 4.3.3. Spatiotemporal analysis .................................................................... 143 4.3.4. Spatial association ............................................................................ 145 4.4. DISCUSSION ............................................................................................... 152 5. MODELLING THE WEATHER CONDITIONS AFFECTING DOWNY MILDEW EPIDEMICS ..................................................................................... 158 5.1. INTRODUCTION .......................................................................................... 158 5.2. MATERIALS AND METHODS ........................................................................ 160 5.2.1. Culture maintenance ......................................................................... 160 5.2.2. Weather monitoring .......................................................................... 161 v 5.2.3. Laboratory studies of sporulation ...................................................... 161 5.2.4. Field monitoring of sporulation ......................................................... 163 5.2.5. Field monitoring of infection ............................................................. 165 5.2.6. Model development ........................................................................... 167 5.2.7. Model evaluation .............................................................................. 172 5.3. RESULTS ................................ ······· ··········· ·············· ................................... 175 5.3.1. Laboratory studies of sporulation ...................................................... 175 5.3.2. Field monitoring of sporulation ......................................................... 177 5.3.3. Field monitoring of infection ............................................................. 178 5.3.4. Model development ........................................................................... 179 5.3.5. Model evaluation .............................................................................. 187 5.4. DISCUSSION ............................................................................................... 193 6. METHODS OF OVERWINTERING BY THE DOWNY MILDEW PATHOGEN ....................................................................................................... 202 6.1. INTRODUCTION .......................................................................................... 202 6.2. MATERIALS AND METHODS ........................................................................ 204 6.2.1. Crop residues .................................................................................... 204 6.2.2. Seed-borne inoculum ......................................................................... 207 6.2.3. Weeds and alternative hosts .............................................................. 213 6.3. RESULTS··································································································· 218 6.3.1. Crop residues .................................................................................... 218 6.3.2. Seed-borne inoculum .. ....................................................................... 220 6.3.3. Weeds and alternative hosts .............................................................. 224 6.4. DISCUSSION ..............................................................................................
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