Reevaluation of systematic relationships in Triticum L. and Aegilops

292 Pages·2012·13.85 MB·English

by  Morrison, Laura A.

AN ABSTRACT OF THE THESIS OF

Laura A. Morrison for the degree of Doctor of Philosophy in Botany and Plant
Pathology presented on October 21, 1994. Title: Reevaluation of Systematic
Relationships in Triticum L. and Aegilops L. Based on Comparative Morphological
and Anatomical Investigations of Dispersal Mechanisms
Redacted for Privacy
Abstract approved:
Kenton L. Chambers
Comparative morphological and anatomical studies of the dispersal mechanisms
characterizing the wheat complex (Triticum L. and Aegilops L.) have documented
patterns of adaptive radiation which may have significance for evolutionary
relationships. These patterns, which form an array of diverse types of diaspores
among the diploid taxa, appear conceptually to have a starting point in the
dimorphic inflorescence of Ae. speltoides. Separate dispersal trends, centered
primarily in features of rachis disarticulation, lead in the direction of novel diaspore
types for Aegilops and in the direction of domestication for Triticum. With respect
to the taxonomy, this structural evidence supports the traditional Linnaean generic
circumscriptions and suggests a need for a monographic revision of Triticum. In
documenting the dispersal mechanisms, these studies have clarified conventional
interpretations and have offered new insights on the developmental relationships
linking the wild and domesticated taxa of the wheat complex. Although genetic
studies were not encompassed within this research, a consideration of the genetic
explanations for rachis disarticulation and glume closure suggests that the phenotypic
traits typically used in genetic studies are not well understood. Given that the
reticulate nature of genomic relationships in the wheats is coupled with intergrading
variation and polymorphic species, a proposal is made for a broader evolutionary
view than is found in the strict cladistic concept. This proposal emphasizes the need
of an improved understanding of fundamental structural traits and an inclusion of
these traits in evolutionary analyses.
°Copyright by Laura A. Morrison

October 21, 1994

All Rights Reserved
Reevaluation of Systematic Relationships in Triticum L. and

Aegilops L. Based on Comparative Morphological and

Anatomical Investigations of Dispersal Mechanisms

by
Laura A. Morrison
A THESIS

submitted to

Oregon State University

in partial fulfillment of
the requirements for the
degree of
Doctor of Philosophy
Completed October 21, 1994

Commencement June 1995
Doctor of Philosophy thesis of Laura A. Morrison presented on October 21, 1994
APPROVED:

Redacted for Privacy
Major Professor, representing Botany and Plant Pathology
Redacted for Privacy
LIVHead of Department of Botany & P1 t o ogy
Redacted for Privacy
Dean of Graduate Sc
I understand that my thesis will become part of the permanent collection of Oregon
State University libraries. My signature below authorizes release of my thesis to any
reader upon request.
Redacted for Privacy
thor
ACKNOWLEDGEMENTS

The research reported in this thesis would not have been possible without the
assistance, guidance, and encouragement of faculty and staff members associated
with Oregon State University and members of the international wheat research
community. I am particularly grateful to those individuals who provided germplasm
material, answered the many questions I posed in correspondence or in meetings at
international conferences, and encouraged my alternative approach to modern
systematic studies in the wheat complex. I offer a special note of appreciation to the
following people who were instrumental in guiding my work: to Kenton L.
Chambers, my major professor, for the freedom which he provided in my pursuit of
the mysteries of wheat evolution; to Robert J. Metzger (Oregon State University),
for his sharing of an encyclopedic knowledge of the wheats; to Dr. J. Giles Waines
(University of California, Riverside), for his support from afar; to Dr. Joachim
Kummerow (Oregon State University), for the many hours of his time devoted to
translating an obscure, but important German literature; to the organizers of the
1992 ICARDA International Workshop on Evaluation and Utilization of Biodiversity
in Wild Relatives and Primitive Forms for Wheat Improvement and the 8th
International Wheat Genetics Symposium (1993) for arranging my attendance at
these two international conferences; and to Lynda M. Ciuffetti and Donald J.
Armstrong (Department of Botany and Plant Pathology) for their wise advice and
counsel, particularly on matters of teaching. I am also grateful to the administrative
staff of the Department. A sincere expression of appreciation to Diane Simpson and
Blaine Baker for all the significant ways in which they helped with my journey
through a PhD program; to Lewis Tate and his assistants for their cooperation and
accommodation of my unusual agronomic needs for the research field at the Botany
and Plant Pathology Field Lab; and to Kevin Currans and Galen Krokum of the
College of Science Biocomputing Consortium for their patient assistance with
computer matters.
Funding for this research was obtained from the Tyson Fellowship Fund of the
Woman's National Farm and Garden Association, Inc., the Northwest Scientific
Association, and the Bonnie Templeton Fund (Department of Botany and Plant
Pathology). Trips to the International Triticeae Symposia (1991, 1993), the
ICARDA International Workshop (1992), and the 8th International Wheat Genetics
Symposium (1993) were funded with donations from private and public sources. I
appreciate the efforts of all those who assisted in large and small ways with the
financial arrangements for these trips. In this regard, I am deeply grateful to Kenton
L. Chambers, Stella M. Coakley (Head, Department of Botany and Plant
Pathology), J. Giles Waines, Warren E. Kronstad and the Oregon Wheat
Commission, Ardeshir Damania (formerly of ICARDA), and my parents, Robert L.
and Marion W. Morrison.
The botanical illustrations contained in Chapters 4 and 5 proved an essential
part of this thesis. For her daring entry into the pictorial world of wheat, I am
indebted to Christine Roberts to whom I wish a prosperous career as an illustrator
should graduate school no longer offer an option. I also appreciate the
supplementary support offered by Pablo Rosso who contributed three illustrations
while emersed in the last stages of his masters degree in Plant Pathology.
To a warm and caring community of friends--Tina Dreisbach, Frank Gecina,
Catharina Coenen, Chris Lundberg, Kyoung-Hee Kim, Jolene and Steven Broich,
Hillary Egna, Marty Fitzpatrick, Robin Wagers, Carolyn Wright, David Gross, and
Barbara Wilson--my sincere gratitude. And to Raan Young, a multitude of thanks
for midnight assistance at the scanner.
TABLE OF CONTENTS
Page
I. INTRODUCTION 1

II. TAXONOMY OF THE WHEATS: A COMMENTARY 4

Abstract 4

Introduction 5

The Taxonomy 7

Taxonomic Deficiencies and Evolutionary Considerations 13

Triticum urartu Thumanjan ex Gandilian 14

Aegilops speltoides Tausch 16

Anomalous Wheat Taxa 18

Conclusion 20

Acknowledgements 21

References 22

III. A MONOGRAPHIC PROJECT TO REVISE THE TAXONOMY

OF TRITICUM L. 26

References 33

IV. DISPERSAL MECHANISMS IN THE WHEAT COMPLEX

(TRITICUM L. AND AEGILOPS L.): ADAPTIVE

RADIATION 35

Abstract 35

Introduction 36

Materials and Methods 42

Clarification of Terminology 43

Inflorescence Structure 63
Page

Historical Perspective 63

Deficiencies in Current Interpretations of

Dispersal Mechanisms 70

Developmental Relationships of Diaspore Types 73

A Reinterpretation of the Adaptive Radiation 75

Wedge Diaspore Class 75

Synaptospermic Diaspore Class 89

Anomalous Dispersal Strategies 101

Spike let Dispersal 101

Floret Dispersal 104

Seed Dispersal 105

Dispersal and Seedling Establishment 109

Passive Dispersal 109

Penetration in the Soil 112

Seedling Establishment 113

Developmental Relationships Within the Tribe

Triticeae 118

Conclusion 121

References 122

V. DISPERSAL MECHANISMS IN THE WHEAT COMPLEX

(TRITICUM L. AND AEGILOPS L.): RACHIS

DISARTICULATION AND GLUME CLOSURE 130

Abstract 130

Introduction 131

Materials and Methods 134

Rachis Disarticulation 135