Table Of ContentRACES OF FUSARHJM OXYSPORUM F. LINI
IN ARIZONA
by
Robert B. Marlatt
A Thesis
submitted to the faculty of the
Department of Plant Pathology
in partial fulfillment of the requirements for the degree of
DOCTOR OF PHILOSOPHY
in the Graduate College, University of Arizona
1952
Approved: UXzAsJ>L\J) t
Director of Thesis
ACKNOWLEDGMENT
Grateful acknowledgment is made to Dr. R.B.
Streets who directed the thesis. The author is
indebted to Dr. J"»G. Brown, Dr. Alice M. Boyle, $nd
Dr* P.D. Keener for critical reading of the manu
script and for their helpful suggestions. Greenhouse
space was generously furnished by Professor W.E,
Bryan, Head of the Department of Plant Breeding.
Acknowledgment is made also to Dr. W.S. Phillips,
Head of the Department of Botany and Range Ecology,
and to Edward L. Breazeale, Assistant Agricultural
Chemist, for valuable aid.
ii
TABLE OF CONTENTS
Section Page
INTRODUCTION 1
Review of the Literature 2
History 2
Symptoms 3
Control 4
The Pathogen . 5
Environment 10
Resistance 14
METHODS AND RESULTS 16
Collection of Cultures 16
Single-Spore Culture Methods 18
Cultural Studies .24
Growth on Potato-Dextrose Agar 26
Growth on Malt Agar 26
Growth on Cornmeal Agar 26
Growth on Rice 27
Anastomosis and Antagonism 33
Germination Tests .... 40
Greenhouse Procedures 45
Investigation of a Bacterial Pathogen 51
Toxin Investigations ... 52
Re-isolation of the Fusarium from Stem Tips ... 68
Pathogenicity Experiment 70
Pathogenicity of Isolates 73
Comparison of Varieties 99
Arizona Isolates Compared with Those from
Other Regions ........ 107
DISCUSSION 109
SUMMARY . . . 116
BIBLIOGRAPHT . . 118
APPENDIX 125
iii
LIST OF TABLES
Number Page
1« Sources of Flax Yielding Fusarium
oxysporum f. lini • 17
2. Approximate Percentages of Macroconidia on
Various Media .... ...... 20
3. Cultures on Potato-Dextrose Agar 28
4. Cultures on Malt Agar 29
5. Cultures on Cornmeal Agar 31
6. Cultures on Rice 32
7o Diameters of Colonies after Six Days Growth.
on Potato-Dextrose Agar . 34
8. Diameters of Colonies after Six Days Growth
on Malt Agar 35
9. Diameters of Colonies after Six Days Growth.
on Cornmeal Agar . 36
10. Diameters of Colonies after Eight Days Growth
on Rice 37
11. Percentages of Flax Seeds Germinated Disin
fected with New Improved Ceresan 41
12. Fungi from Flax Seeds Disinfected with New
Improved Ceresan . 43
13. Percentages of Flax Seeds Germinated
Disinfected with. Alcoholic Mercuric
Chloride 44
14. Fungi from Flax Seeds Disinfected with
Alcoholic Mercuric Chloride . 45
15. Effect of Soil Mixtures on Flax Emergence . . 47
16. Change in Soil during One Month in the
Greenhouse . 48
iv
Number Page
17. Effect of Toxic Filtrate on Punjab Flax Seeds 55
18. Effeot of Toxic Filtrate on Punjab Flax Seeds 57
19. Effect of Toxic Filtrate on B 5128 Flax Seeds 58
20. Effeot of Toxic Filtrate on Seeds of Ten
Flax Varieties 60
21o Flax Varieties Listed in Increasing Order
of-Susceptibility to Filtrate . 66
22. Reaction of Punjab to Isolates. ....... 74
23. Reaction of Bison to Isolates 76
24. Reaction of Linota to Isolates 78
25. Reaction of Pergamino to Isolates ...... 80
26. Reaction of Redwing to Isolates ....... 82
27. Reaction of NDR 114 to Isolates 84
28. Reaction of C.I. 1164 to Isolates 86
29. Reaction of B 5128 to Isolates 88
30. Reaction of No. 21 to Isolates 90
31. Reaction of No. 22 to Isolates. ....... 92
32. Isolates in Order of Decreasing Pathogenicity
to Ten "Varieties of Flax 95
33. Isolates in Order of Decreasing Pathogenicity
to Ten Varieties of Flax Determined by
Wilt after Emergence 96
34* Isolates in Order of Decreasing Pathogenicity
to Ten Varieties of Flax Determined by
Amount of Emergence 100
35. Isolates in Order of Decreasing Pathogenicity
to Ten Varieties of Flax Determined by
Number of Survivors after.5 0 Days 101
36. Varieties in Order of Decreasing Resistance
Determined by Average Per Cent Wilt with
all Isolates 103
Number Page
37. Varieties in Order of Decreasing Resistance
Determined by Susceptibility and
Resistance to Isolates 104
38. Varieties in Order of Decreasing Resistance
Determined by Susceptibility and
Resistance to Isolates • . . 105
39. Varieties in Order of Decreasing Resistance
Determined by Susceptibility and
Resistance to Isolates ..... 106
40. Comparable Isolates of Minnesota and Arizona
Tests . . 108
vi
LIST OF FIGURES
. (in Appendix)
Number
1. Map of the Yuma Area
2. Cajnera Luoida Drawing of Fusarium oxysporumf . lini
Macrooonidium during Germination
3. Slide Bearing a Thin Layer of Agar for Obtaining
Single Spores
4. Slide Bearing a Thin Layer of Agar for Observing
Anastomosis
5. Examples of Cultural Types
6. Pot Protected from Rodents and Insects
7. Rice Culture used for Soil Inoculation
8. Culture Chamber
9. View of Greenhouse Experiment
10. Effects of Toxic Filtrate on Punjab Seed Germination
11. Fusarium Growing from a Stem Tip
12. Wilt caused by a Fusarium isolate
vii
I N T R O D U C T I O N
Recent studies of flax wilt by Streets( 1950, 1951) of
the Arizona Agricultural Experiment Station have shown that
the disease is becoming a limiting factor in flax culture
and that the most satisfactory control measure is the sub
stitution of wilt-resistant varieties for the very suscepti
ble commercial variety, Punjab.
Some varieties, resistant when grown int he Imperial
Valley in California, are very susceptible when grown in the
Yuma Valley of Arizona, suggesting the existence of physio
logical races of the fungus differing in their pathogenicity
to certain varieties of flax. Investigators have reported
the existence of physiological strains in other areas. The
value of resistant varieties of flax for Arizona depends upon
a determination of what races of the wilt fungus are present,
so that flax varieties having the proper resistance can be
recommended.
Isolation of the various races can be useful as a
means of providing the University flax-wilt plot with dif
ferent strains of the fungus so that flax-breeding experi
ments being carried on may produce flax resistant to the wilt
organism in the various fields of the state.
Observance of cultural traits of the strains of the
fungus may provide some means of classifying them under
2
laboratory conditions and of relating them to those races
obtained in other parts of the world.
Review of the Literature
A review of the pertinent literature has been made in
order to provide a source of information useful for this and
for later work on the problem*
History; It is known that flax (Linum usitatissumum L.)
has been cultivated for at least six thousand years, but the
first mention of the wilt disease was probably made by
Pliny (translated 1856) who remarked: "It has the property
of scorching the ground where it is grown and of deterio
rating the quality of the very soil itself," Until the nine
teenth century, no one knew any more about the cause of flax
wilt disease than did Pliny in the first century. Finally
in 1893, Broekema (1893) separated the disease from others
and suspected its parasitic nature. He selected surviving
plants from an infested field and noted that their seed gave
rise to a generation of flax which was somewhat resistant to
the disease. Shortly thereafter in 1897 Nypels described a
disease of flax in the Flanders area which he called "la
brulure du lin," which probably was flax wilt (Barker, 1923).
In Japan, Hiratsuka first reported that the disease was
caused by a Fusarium in 1896. Bolley in 1901 described the
fungus and named it Fusarium lini. By selection methods
Bolley obtained varieties of flax which were resistant to
the disease, and the flax industry was no longer destinedt o
3
move from "flax-siok" regions to areas where flax had never
been cropped before.
The first important commercial production of flaxseed
in California was the eleven thousand acres planted.in the
Imperial Valley in 1934. This was the outgrowth of variety
trials begun in 1927 at the Imperial Valley Experiment Sta
tion near El Centro. Wilt was not as yet reported from the
far western states when Dillman and G-oar (1937) wrote on
flaxseed production in these areas.
Flax was grown experimentally in Phoenix,A rizona, as
early as 1914. Mention was made of variety tests being con
ducted by the Experiment Station in the University of Arizona
Agricultural Experiment Station's annual reports for 1915,
1916 and in later years.
Symptoms: In reporting on the wilt disease of flax, it
was stated by Bolley (1901) that most susceptible plants are
killed by the fungus before emerging from heavily infested
soil. The organism was isolated by Schuster (1944) from
primary roots of the flax plant on the day of emergence, and
was found in the apex of plants seven days after emergence.
Boyle (1934) reports that the whole root stele was invaded
in flax twenty days old. However, Tisdale (1917b) found no
considerable clogging of the vascular system by the ffusarium,
despite the occurrence of microconidia in the vessels. The
wilting may be partially explained by the fact that Millikan
(1949) found a toxic substance which was formed by the fungus
and which caused wilt symptoms. Grossman (1934) noted that a
