Evaluation of PCR-Based Methods for Rapid, Accurate Detection and Monitoring of Verticillium

165 Pages·2017·2.37 MB·English

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Theses and Dissertations--Plant Pathology Plant Pathology
2014
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Baker Diwan Getheeth Aljawasim
University of Kentucky, [email protected]
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Aljawasim, Baker Diwan Getheeth, "Evaluation of PCR-Based Methods for Rapid, Accurate Detection and
Monitoring of Verticillium Dahliae in Woody Hosts by Real-Time Polymerase Chain Reaction" (2014).
Theses and Dissertations--Plant Pathology. 13.
https://uknowledge.uky.edu/plantpath_etds/13
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Baker Diwan Getheeth Aljawasim, Student
Dr. Paul Vincelli, Major Professor
Dr. Lisa J. Vaillancourt, Director of Graduate Studies
EVALUATION OF PCR-BASED METHODS FOR RAPID, ACCURATE
DETECTION AND MONITORING OF VERTICILLIUM DAHLIAE IN
WOODY HOSTS BY REAL-TIME POLYMERASE CHAIN REACTION

THESIS

A thesis submitted in partial fulfillment of the requirements for the degree of
Master of Science in the College of Agriculture, Food, and Environment at the
University of Kentucky
By
Baker Diwan Getheeth Aljawasim
Lexington, Kentucky
Director: Dr. Paul Vincelli, Professor of Plant Pathology
Lexington, Kentucky

2014
Copyright© Baker Aljawasim 2014
ABSTRACT OF THESIS

EVALUATION OF PCR-BASED METHODS FOR RAPID, ACCURATE
DETECTION AND MONITORING OF VERTICILLIUM DAHLIAE IN
WOODY HOSTS BY REAL-TIME POLYMERASE CHAIN REACTION

Verticillium wilt, caused by Verticillium dahliae Kleb, is one of the most
economically important diseases of woody hosts such as ash (Fraxinus spp.),
sugar maple (Acer saccharum), and redbud (Cercis canadensis). The causal agent
has a broad host range, including not only woody hosts but also important
vegetable and field crops, and it is distributed worldwide. Diagnosis of V. dahliae
in infected woody hosts is often based on the occurrence of vascular discoloration
and time-consuming isolation. However, not all woody hosts exhibit vascular
discoloration symptoms, and not all vascular discoloration symptoms are due to
infection by V. dahliae. In this study, real-time PCR-based assays were evaluated
and employed for rapid and accurate detection of V. dahliae in different woody
hosts. DNA was extracted in large quantities from presumptively infected woody
hosts by collecting drill-press shavings from sample tissue, bead-beating, and
extracting using a CTAB method. Six published primer sets were evaluated
against genomic DNA of V. dahliae as well as selected negative controls, and two
sets (VertBt-F/VertBt-R and VDS1/VDS2) showed promise for further evaluation
using DNA extracts from field samples. The VertBt primers amplified a species-
specific 115-bp fragment of the expected size, while the VDS primers amplified
the expected specific 540-bp fragment. However, the VertBt primer set exhibited
higher sensitivity in detection of V. dahliae even in asymptomatic trees. The
PCR-based methods developed here could be used as rapid tools for pathogen
detecting and monitoring, thus informing plant pathogen management decisions.

KEYWORDS: Verticillium dahliae, Verticillium wilt, real-time PCR, woody
plants.
Baker Aljawasim

Apr 8th 2014
EVALUATION OF PCR-BASED METHODS FOR RAPID, ACCURATE
DETECTION AND MONITORING OF VERTICILLIUM DAHLIAE IN
WOODY HOSTS BY REAL-TIME POLYMERASE CHAIN REACTION

BY
Baker Diwan Getheeth Aljawasim

Dr. Paul Vincelli

Director of Thesis

Dr. Lisa J. Vaillancourt
Director of Graduate Studies

Apr 8th 2014
To my family, my father, my mother, my friends, and especially Higher
Committee for Education Development in Iraq (HCED)
ACKNOWLEDGEMENTS

First of all, I would thank my advisor, Paul Vincelli, for his support,
guidance, and patience with me during my work in University of Kentucky. I
think any student will be grateful to work with a great person like him. Dr. Paul
taught me the fundamentals of science, and how can I think as a scientist to
overcome any problem during my career. I would like to extend my gratitude to
my committee members Dr. Nicole Ward Gauthier and Dr. A Bruce Downie for
their helpful advice and instructions.
I greatly appreciate the extensive support offered by Extension Plant
Pathology staff members (Bernadette, Ed, Julie, Sara, and Doug). Especially, I
really want to express my deep gratitude to Bernadette for her extensive support,
assistance, and help with my experiments in the laboratory. Also, I want to thank
Dr. K. Subbarao from University of California, Davis for providing us isolates of
V. dahliae. I would like to thank all the graduate students in the Plant Pathology
Department at the University of Kentucky for their help and support. Also, I
would like to thank all faculty and staff of the Department of Plant Pathology,
especially Dr. Christopher L. Schardl, Dr. Lisa Vaillancourt, Dr. Mark Farman,
Dr. Pradeep Kachroo, Dr. Aardra Kachroo and, Dr. Kenneth W. Seebold, Shirley
Harris, and Alicia Landon for their support and help.
Lastly, I sincerely thank the Higher Committee for Education
Development (HCED) in Iraq for their great support and confidence in me, and I
hope to pay my country back by participating in Iraq‟s development, especially in
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agricultural disciplines. I will not forget my father, my mother, my brothers, and
my sister for supporting and praying for me to achieve all my dreams. I will
never forget that my father said “Go to United States and get your degree, and all
people in your neighborhood will support you,” and my mother‟s tears when I left
my country. I hope that I can achieve my big dream by earning my PhD degree
from United States as well. Actually, I am grateful for being at the University of
Kentucky not only for high level of education but also for great culture and
atmosphere for studying.

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TABLE OF CONTENTS

ACKNOWLEDGEMENTS ............................................................................................. iii
LIST OF TABLES .......................................................................................................... vii
LIST OF FIGURES ........................................................................................................ viii
CHAPTER ONE: LITERATURE REVIEW .................................................................... 1
I. Verticillium Wilt ............................................................................................... 1
History of Verticillium Wilt.................................................................. 2
Classification of V. dahliae ................................................................... 4
Morphological and Anatomical Characters .......................................... 6
Disease Cycle ........................................................................................ 8
Symptoms ........................................................................................... 11
II. Management of Verticillium Wilt ................................................................... 14
Physical Methods ................................................................................ 14
Chemical Methods .............................................................................. 17
Fertilization Methods .......................................................................... 21
Biological Methods ............................................................................. 23
Resistant Cultivars .............................................................................. 26
III. Traditional Detection Methods for V. dahliae ................................................ 27
Detection of Microsclerotia from the Soil .......................................... 28
Selective Media Methods .................................................................... 29
Staining Methods ................................................................................ 30
IV. Polymerase Chain Reaction (PCR) ................................................................. 31
V. DNA-Based Detection of V. dahliae .............................................................. 36
CHAPTER TWO: Evaluation of PCR-Based Methods for Rapid, Accurate Delectation
and Monitoring of Verticillium dahliae in Woody Hosts by Real-Time
Polymerase Chain Reaction .................................................................. 40
Introduction ........................................................................................................... 40
Materials and Methods .......................................................................................... 44
Results ................................................................................................................... 56
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Discussion ............................................................................................................. 67
LITERATURE CITED .................................................................................................. 121
VITA …………………………………………………………………………...144

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