STUDIES OF PLANT HOST PREFERENCES OF THE STEM NEMATODES, DITYLENCHUS WEISCHERI AND D. DIPSACI BY ABOLFAZL HAJIHASSANI A Thesis Submitted to the Faculty of Graduate Studies of The University of Manitoba in Partial Fulfillment of the Requirements for the Degree of DOCTOR OF PHILOSOPHY Department of Soil Science University of Manitoba Winnipeg, Manitoba Copyright © May, 2016 i ABSTRACT Hajihassani, Abolfazl. Ph.D., The University of Manitoba, May 2016. Studies of plant host preferences of the stem nematodes, Ditylenchus weischeri and D. dipsaci. Major Professor: Dr. Mario Tenuta. The occurrence of D. weischeri Chizhov, Borisov & Subbotin, a newly described stem nematode species of creeping thistle (Cirsium arvense L.), and D. dipsaci (Kühn) Filipjev, a pest of garlic and quarantine parasitic species of many crops, has been reported in Canada. This research was conducted to determine if D. weischeri is a pest of agricultural crops, especially yellow pea (Pisum sativum L.) in the Canadian Prairies. Significant (P < 0.05) slight reproduction (1 < ratio of final to initial population < 2) of D. weischeri occurred on two (Agassiz and Golden) of five varieties of yellow pea examined. Other annual pulse and non-pulse crops, including common bean, chickpea, lentil, spring wheat, canola, and garlic were non-hosts for D. weischeri. Conversely, a range of reproduction responses to D. dipsaci was observed with all pulse crops being a host of the nematode. Ditylenchus weischeri was not a seed-borne parasite of yellow pea, unlike, D. dipsaci which was recovered from seed. Conversely, D. weischeri and not D. dipsaci was recovered from creeping thistle seeds. In callused carrot disks, with no addition of medium, an increase of 54 and 244 times the addition density of 80 nematodes was obtained for D. weischeri and D. dipsaci, respectively, after 90 days. Temperature had a significant influence on the development of D. weischeri and D. dipsaci in yellow pea. Development of D. weischeri did not proceed past adult stage at 17 and 22°C whereas a minimum generation time of 30 days was apparent at 27°C with the associated accumulated growing degree-days of 720 degree-days (above a base ii temperature of 3°C). The minimum generation time for D. dipsaci was 24, 18 and 22 days with 336, 342 and 528 degree-days at 17, 22 and 27°C, respectively. In field microplots, grain yield of yellow pea were not significantly affected by addition density of D. weischeri. At harvest, the total number of recovered nematodes per plant was not significantly different than the added at the start. The results of these studies confirm that D. weischeri is unlikely to be a pest of yellow pea for weather conditions of the Canadian Prairies. iii ACKNOWLEDGMENTS I firstly would like to sincerely thank my main advisor, Dr. Mario Tenuta, for guidance, suggestion, support, encouragement, and enthusiasm. He has been a respected mentor throughout my program, provided helpful advice, and always took time to help me. I appreciate all his contributions of time and ideas to make my PhD experience productive and stimulating. I would like to express my warm and sincere thanks to my co-advisor Dr. Robert H. Gulden who was always available whenever I had a question or needed advice; I greatly appreciate his incredible help, support, kindness, and encouragement. I thank my advisory committee member Dr. Don Flaten for his guidance and constructive suggestions. I also express gratitude to Dr. Paul Bullock, head of the department of soil science, for his support and enthusiasm. I would like to thank all the members of Soil Ecology Lab, especially Brad Sparling, Mervin Bilous, and Matthew Gervais for their friendship and technical assistance. Also, I offer my gratitude to the faculty, and technical and administrative staff at the Department of Soil Science for their support and encouragement. I thank Dr. Fouad Daayf and Lorne Adam for their help. Lastly, thank you to the friends I made here in Winnipeg for your amazing support and unforgettable memories. I sincerely thank the Alberta Pulse Growers, Manitoba Pulse and Soybean Growers, Saskatchewan Pulse Growers and Agriculture and Agri-Food Canada (AAFC) through the Pulse Science Cluster II Project of the AAFC Growing Forward II program for financial support. I would like to thank Drs. Michael Celetti for supplying garlic bulbs infested with D. dipsaci, Bert Vandenberg, Tom Warkentin and Robert Conner as well as Brad Barlow for providing yellow pea seeds. Special thanks are owed to my parents so far away in Iran, whose have supported me throughout my years of education, both morally and financially. Finally, I deeply would like to thank my wife, Negin Hamidi, for any inconvenience I caused her during my program. Thank you for giving me the strength and motivation to finish the thesis work. iv Table of Contents Content Page ABSTRACT....................................................................................................................... ii ACKNOWLEDGMENTS................................................................................................. iv TABLE OF CONTENTS................................................................................................... v LIST OF TABLES............................................................................................................ ix LIST OF FIGURES............................................................................................................ x LIST OF ABBREVIATIONS............................................................................................ xi FOREWORD................................................................................................................... xiii 1.0 GENERAL INTRODUCTION ..................................................................................... 1 2.0 LITERATURE REVIEW ............................................................................................. 6 2.1 Creeping thistle: D. weischeri host plant ................................................................ 6 2.1.1 Background .................................................................................................... 6 2.1.2. Morphology of creeping thistle .................................................................... 7 2.1.3 Distribution and ecology of creeping thistle .................................................. 8 2.2.4 Control methods of creeping thistle............................................................. 10 2.2 Yellow pea: main study plant of thesis ................................................................. 11 2.2.1 Background .................................................................................................. 11 2.2.2 Brief history of the Pea ................................................................................ 12 2.2.3 Economic importance of pea ....................................................................... 13 2.2.4 Field pea in Canada ..................................................................................... 14 2.2.5 Diseases and nematode pests of pea ............................................................ 17 2.3 Stem nematodes (Ditylenchus spp.) ...................................................................... 19 2.3.1 Ditylenchus genus ........................................................................................ 19 2.3.2 Taxonomic position of Ditylenchus ............................................................. 20 2.3.3 The most significant species of the genus Ditylenchus ............................... 21 2.4. Stem nematode of creeping thistle, Ditylenchus weischeri .................................. 22 v 2.4.1 Background and identification..................................................................... 22 2.4.2 Hosts and symptoms of Ditylenchus weischeri .......................................... 26 2.5 Stem and bulb nematode (Ditylenchus dipsaci) .................................................... 27 2.5.1 Background and distribution of D. dipsaci .................................................. 27 2.5.2 Ditylenchus dipsaci in Canada .................................................................... 27 2.5.3 Morphological identification of Ditylenchus dipsaci .................................. 29 2.5.4 Molecular identification of Ditylenchus dipsaci ......................................... 31 2.5.5 Hosts of Ditylenchus dipsaci ....................................................................... 33 2.5.6 Host-parasite relationship of Ditylenchus dipsaci ....................................... 34 2.5.7 Crop loss caused by Ditylenchus dipsaci .................................................... 35 2.5.8 Disease symptoms caused by Ditylenchus dipsaci ...................................... 37 2.5.9 Biology and survival of Ditylenchus dipsaci ............................................... 39 2.5.10 Effect of environmental conditions on Ditylenchus dipsaci ...................... 40 2.5.11 Nematode management strategies ............................................................. 40 3.0 HOST PREFERENCE AND SEED-BORNE TRANSMISSION OF DITYLENCHUS WEISCHERI AND D. DIPSACI ON SELECT PULSE AND NON-PULSE CROPS GROWN IN THE CANADIAN PRAIRIES .................................................................... 51 3.1 Abstract ................................................................................................................ 51 3.2 Introduction .........................................................................................................