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Root rots of some garden crops

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ROOT
ROTS
OP
SOME
GARDEN
CROPS
Thesis
presented in partial fulfillment
for
the degree of Master of Arts
at
The University of Western Ontario
I9kl
fcy
Margaret A. M. Pettipher
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UMI Number: EC54095
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Table of Contents
Introduction
........
Historical Review
'1
......
2
Aim .......
9
Materials
9
.....
Methods
A.
Isolation methods ......................
10
B*
Inoculation Methods
1h
Experimental Results
Tables I - III
Summary
Literature Cited
..... .
.....
l6
Discussion of each
......
27
......
29
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HOOT
ROTS
Of
SOME
GARDEN
CROPS
Introduction
The study of root rots of cereals has been recognized as
a national problem for over twenty five years, ever since Bolley
first advanced his theory that root rots were chiefly responsible
for much of the increasing unproductiveness of our wheat lands.
But the problem of vegetable root rots has continued to remain
local in character, since it is largely concerned with special
garden crops that are being grown, in limited areas, for export
or canning purposes.
That all micro-organisms, capable of producing root rots
in our garden vegetables, are fungi seems highly improbable.
However, the present paper is entirely concerned with fungi con­
nected with root rots, and with the role played by them in attack­
ing young seedlings especially.
The investigation was carried on over a period of eight
months, beginning in September 19^0, and experiments were per­
formed in the greenhouse at the University of Western Ontario.
The initial collection of material was made from a wide range
of vegetables grown in various localities around London.
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- 2 -
Historical Review
Apparently one of the first reports of a vegetable root
rot caused by a fungus, was made in 1850, when a root rot of
peas due to Thlelavla basicola Zopf., was reported from England.
This same fungus, which produces root rots of lupines, turnips,
beans and violets, was first reported in America in 1891*
However, during the 1890's and early 1900's the role
played by fungi in the root rot problem was pushed into the back­
ground by 1. 7. Smith's (16) and others outstanding investiga­
tions of bacterial diseases of plants. Many investigators con­
sidered the bacteria they isolated from plants suffering with
root rot as the causes of the disease, yet they frequently failed
to reproduce the disease in subsequent inoculation experiments
with these bacteria.
The presence of bacteria as secondary in­
vaders of diseased roots is now well known. Doubtless many of
the bacteria isolated then were, in reality, only saprophytes,
and hence were incapable of invading healthy tissue.
By 1896, the continued severity of a root disease of
tomatoes — commonly known as tomato blight or yellow blight —
compelled the Washington State Experiment Station to undertake
an investigation of the cause of the disease, which was very
prevalent in the Snake, Columbia, and Yakima river valleys.
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Early
investigations were carried out by C. V. Piper from 1696 -
1902*
He made several pure culture isolations of bacteria from
the diseased plants* but was able to reproduce the disease in
only one series of inoculation experiments made with one of his
cultures* His successors* believing that bacteria were the
causal organisms* made numerous unsuccessful attempts to recover
the parasite from the aerial parts of the plant*
In 1909* the project was assigned to H* B* Humphrey (10)»
who successfully isolated the causal organisms from the roots*
These pathogens were fungi I Fusarium orthoceras App* & Wollw**
and rosarium oxysporum (Schlecht)* Both produced *prompt and
severe root infection**
Drechsler (5) reports, in 1927* that two members of the
Saprolegniaceae are capable of producing rootlet injury in
tomatoes* The organisms responsible are Aphanomyces eutelehes,
which is also associated with pea root rot, and Plectospira
ayrjandra*
A previous report of fungi in connection with a root rot
was made in 1903* V Van Hall* who reported that Fusarium vug*
infectufl Atk* was the cause of St*Joha*s disease of peas in
Holland* However* his pathogenicity tests were indefinite* and
subsequent experiments by Jones (11) have indicated that this
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fungus is not Tory pathogenic, Wollenweber (22) Mad Appel, who
classified Van Hall's pathogen as Fusarium falcatum, claim that
"more than one species of fusariumM nay cause St.John's disease,
from 1911 - 1919 further reports , by European and American
investigators, of root rots of garden peas included identifications
of other species of Vasarium by Gueguen, Mortensen, Turessan, Gif*
ford and Levis, .Fusarium orthoceras was isolated by Levis in 1913,
and fusarium redolens and fusarium oxysporum by Wollenweher in
1913 And 191^, Later work by Jones (11) in 1923 indicates that P.
redolens is only weakly parasitic, and that the only fusarium par­
asitic on peas in the United States is f^ marti war, pisi, which
was isolated by Westerdijk in 1915 as a possible cause of St. John's
disease of peas. Jones however claims that these are less importand than Aphanomyees injury.
The mose recent report on the pea root rot problem by
Harter (9) in 1938. indicates that the greatest root rot losses
are due to Phycomycetes. particularly Pythium and Aphanomyces.
Nevertheless he has frequently isolated a very vigorous fusarlum parasite which kills pea seedlings almost as soon as they
emerge.
This fungus agrees best with Fusarium coeruleum and pro­
duces symptoms identical with those produced by Jones' F. mart!
pisi.
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- 5-
Investigations into the corn root rot problem appear to
have begun to bear fruit about 1889* when Burrill (3) described
a bacterial disease of corn roots but since his original work
has not been confirmed Branstetter (l) feels that something else
besides bacteria was responsible for the disease. Years later
losen (1*0 re-examined Burrill*s original specimens and claimed
that these exhibited symptoms similar to those produced by
Diplodia zeae.
The first report of a fungus parasite of corn roots was
made in 1910 by Selby (15), who observed a corn root rot caused
by a species of fusarium.
Pammel (13) described corn root rot
in 191*+• In that year losses due to corn root rot in Iowa amount­
ed to $15*000,000.
By 1918 the corn root rot problem had become of such
national importance that the United States Department of Agri­
culture organized a project to investigate the problem: "Corn
root, stalk and ear rots.* The project listed the following
fungi as harmful: G-ibberella, fusarium, Verticillium, Rhizopus,
and the bacterium, Pseudomonas. G-ibberella sauhinetil (Mont.)
Sacc. was held to be responsible for the greatest amount of
root rot, but Valleau (21), in a 1920 report, claims that
fusarium monillforme is a more active parasite.
Manns and Phillips (12) list four principal organisms
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m
6
m
associated with, root rot of corn seedlings.
These are: Fusarium
moniliforme Sheldon, G-ibberella saablnetll (Mont) Sacc., Diplodla
zeae (Schw) lev., and Cephalosporium saechari Butter.
Branstetter (1) worked on the problem in Missouri in 1927
and came to the conclusion that Biplodia zeae, Fusarium monili­
forme, Cephalosporium acremonium, and Gibberella saubinetil were
capable of producing root rot in seedlings only, and that true
corn root rot which develops as the plant reaches maturity is
caused in Missouri by a soil-borne Pythium-like fungus.
Valter H. Burkholder (2) claims to be the first to report
a dry root rot of the bean including lima beans which are sus­
ceptible.
He warns against confusing dry root rot with two other
root diseases of beans: Khizoctonia blotch and black root rot
due to Thielavla basicola, previously reported as causing pea
root rot in 1850,
(See page 2). The Burkholder report of dry
root rot was made in 1916.
The causal organism was Fusarium
martii phaseoH. lima beans have also been reported as sus­
ceptible to Phymatotrlchum root rot of onions.
This was re­
ported by Taubenhaus (19) in 1929*
When Selby (15) reported a fungus in connection with
corn root rots in 19*0, mention was also made of a Fusarium
bulb rot of onions.
Many species have been Isolated from this
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rot but Fusarium cepae and Fusarium zonatum were consistently
pathogenic.
Davis and
Reddy
(h) in 1932 indicate that there is
a seedling hlight stage of onion bulb rot.
The pink root of onions was first reported from Texas hy
J. J. Tanhenhaus and Mally (20) about 1917* The organism isolated
was Fusarium aalli, but its ability to reproduce the disease was
so poor that Taubenhaus and Mally concluded that other species
Shsarium may be necessary to increase this. H. N. Hansen (8)
was only able to produce pink root rot when Phoma terrestris was
combined with F. malll, so concluded that the latter was a sec­
ondary parasite.
Phymatotrichum root rot reported in 1929 by
Taubenhaus and Ezekiel (19) is also pathogenic on tomato, onion,
and lima bean roots.
In 1921 spinach in Texas suffered from a very serious
attack of wilt.
Taubenhaus (18) succeeded in Isolating the
causal organism Fusarium solaril which normally parasitizes
Irish potatoes. A similar wilt due to Fusarium spinaciaS
was reported from Idaho in 1923* Taubenhaus claims that
Ihizoctoaia frequently opens the way for infection of spinach
with Fusarium species.
The 1935 - 1937 Progress Report of the Dominion Botanist
(7) indicates the presence of a corn root rot at St. Catharines,
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Ontario. She parasitic organisms isolated were Fythium,
Helminthosporium, and Fusarium. which were parasitic to
varying degrees on corn, sugar beet and tomatoes.
The same
report contains mention of an onion root rot near St. Catharines
and also a Fasarium wilt of spinach at Summerland, B. C.
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9
Aim
She aim of the present investigation was to identify
those fungi associated with root rots of our commonest garden
vegetables, and to determine their relative pathogenicity on
seedlings.
Materials
The organisms isolated in connection with root rot
were obtained from two main sources.
(a) from mature roots collected during September
and October from various localities in the vicinity of Lon­
don, and
(b) from roots of vegetables growing in the green­
house on soils previously collected from four widely
separated areas. The areas chosen were as follows:
A. North Thames district.
Soil from a cabbage
field.
B.
Cowln farm.
Same district as A, but two miles south at the
Soil from wheat field.
G. Brescia Hall corn field.
D. Oxford Street, west.
Mature roots collected during the fall included the
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- 10 -
following: corn,'beans, cabbages, onions, Swiss chard,
parsnips, tomatoes, beets, and radishes.
Vegetables grown in the greenhouse on the four soils
were: beans (Golden Wax), lima beans, peas, onions, corn
(Golden Bantam), lettuce, beets, parsnips, carrots, celery,
Swiss chard, radishes, tomatoes and broccoli.
These were
examined at the end of six weeks for evidence of root rots.
Methods
Methods employed daring the investigation have been
divided into two categories, viz.: (A) isolation methods
and (B) inoculation methods.
A.
Isolation Methods
These are concerned entirely with the isolation of
fungi from roots, showing evidence of root rot.
All roots to be examined were first washed very care­
fully in running water, and any showing root rot symptoms,
such as browning or definite lesions, were sterilized in
1/1000 mercuric chloride.
The amount of sterilization nec­
essary depended somewhat upon the size of the roots being
treated, but the usual period ranged from fifteen to forty-
five seconds. The most satisfactory results were obtained
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- 11
when roots were sterilized between thirty and forty-five
seconds, since at shorter periods than this, bacteria over­
ran the cultures; while, at longer periods, penetration by
the mercuric chloride was sufficient to kill all organisms
present in the roots.
The sterilized roots were immediately washed in two
changes of sterile distilled water.
Frequently a sterilized
scalpel was used to cut open the roots in order to facilitate
the emergence of the fungi.
fhe infected roots were then planted on agar and in­
cubated at 24° C for twenty-four to seventy-two hours.
The formula for the agar used was as followsi
•3$ beef extract,
•5$ peptone,
1.5$ agar,
39$
potatoes
Distilled water * 1000 cc.
A potato decoction was made by boiling the potatoes in 800 cc.
of distilled water for about half an hour. The liquid was then
filtered and enough distilled water added to make up for evap­
oration losses.
The beef extract - peptone - agar mixture
was dissolved in the remaining 200 cc. of water, by heating
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- 12 -
it in the autoclave under 15 lbs. pressure for 15 minutes.
Any losses due to evaporation were restored, and the two
liquids were mixed, tubed and sterilized.
Hyphae emerging from the sterilized roots were
identified at once and transferred to agar slants.
Pure
cultures were prepared by the agar "streak plate" method,
and from these were prepared monospore cultures for sub­
sequent pathogenicity tests.
The "loop dilution" method proved to be the most
satisfactory means of obtaining man©spore cultures.
The
inoculating needle was Just touched to the hyphae and then
transferred to a tube of cooled melted agar. The organisms
were mixed thoroughly and then the agar was poured into sterile
petri dishes. Very clear agar was essential. All cultures
were re-examined within twelve hours and an isolated germin­
ating spore was then transferred to an agar slant.
In some cases a special malt agar, recommended by
Clara Fritz (6), was used for certain Fusarium cultures,
which would produce only chlamydospores and microconidia
after the third or fourth transfer had been made.
It was
found that these cultures would again produce macroconidia,
which were however usually reduced in size.
The formula used
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25 gins* extract of malt,
25 gins, agar
1 L. distilled water.
The agar was soaked overnight and the unassorted water replaced
"by an equal amount containing the malt extract.
This was than
steamed for 20 minutes at 15 Its. pressure, strained, tuhed
and sterilised.
Fusarium strains isolated during the investigation were
very difficult to identify fry their macroconidia alone.
Therer
fore, they were grouped according to growth and color features*
The medium used was that recommended fry Sherfrakoff (17) to
show up color differences.
Potato
The formula was the following:
200 gms,
Agar
20 gms,
Olucose
50 gms,
Distilled water 1000 cc.
To 1000 cufric centimeters of a potato decoction were added
the agar and glucose, and the whole was cooked for 20 min­
utes at 15 lfrs. pressure. After carefully filtering to
obtain a very transparent medium, the tubes of agar were
sterilized.
The above medium was extremely helpful in the pre­
paration of single spore cultures.
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-
£.
i4 -
Inoculation Methods
These were necessary in order to determine the
pathogenicity of organisms obtained hy means of the is­
olation methods previously described.
In order to limit the problem of secondary organ­
isms as far as possible, the tests were performed under
more or less aseptic conditions.
Therefore all seeds
used were sterilized.
The period of sterilization had to be varied some­
what to suit the seed, but broadly speaking the seeds used
were sterilized from two to eight seconds. Radish and let­
tuce seeds were only able to withstand two seconds without
having their germination power seriously affected; but beans,
Swiss chard, corn, and peas were sterilized for eight seconds*
Seed were then transferred to (l) sterile filter paper
in sterile petrl dishes, and incubated at 2*f° C., (2) to soil
which had first been sterilized at 15 lbs. pressure for tyj
minutes.
The inoculum for the petri dish experiments was agar
on which a monospore culture of the fungus was growing.
This
was placed beneath the roots of healthy seedlings and in con­
tact with them.
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Inoculum for the soil experiments was prepared by
growing the fungus on sterile oatmeal, which was eventually
mixed, by means of a sterile scalpel, into the soil* fhe
sterile seeds were then transferred to this and the flat was
placed tinder a humidor which had been washed with l/lOOO
mercuric chloride, fhe purpose of the humidor was to cut
down external contamination to a minimum.
Seedlings in the petri dish experiments were examined
regularly; but at the end of a week any showing symptoms of
root rot were removed, re-sterilized and plated out on agar,
fhe number of re-isolations of the fungus under consideration
at the time was recorded.
In the case of seedlings growing on inoculated soil,
examination of their roots was made three weeks after planting.
Ee-isolations were also made from .any showing evidence of
attack.
fhe pathogenicity of the fungi isolated by method A
was determined by these inoculation experiments and the
results were tabulated.
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- 16 -
Experimental Results
Results of Isolation Experiments
Discussion
Results of the experiments performed in order to
isolate fungi from root rots are summarized by Table I.
In most cases, external evidence of root rot, as
Indicated by the above ground portions of the plant, was meagre*
An exception was provided by corn and peas, the leaves of
which were occasionally yellowed*
In severe cases of root rot infection in corn and
peas, the radicle was destroyed by the time the plumule was
an inch above ground.
Stands were consistently poor with peas grown on soil
A*
In one experiment six out of eight peas failed to appear
above ground. Examination revealed that the radicles, in
all cases, were badly rotted and completely permeated by
Fusarium 17. Evan the two which emerged above ground, had
lesions caused by this fungus.
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TABLE I - Fungi isolated from root rots of garden crops.
Host
Location of Host Age of
Plant
Beans (G.W.) *London Garden
Soil B
Mature
Seedlings
Evidence of Soot Rot
General
jAppearance of Roots
Appearance Appearance of
Leaves and Stem
of Stand
Good
tt
Organisms
Isolated
Slight wilting
Generalized Browning
Fusarium IV
Hormal
Blackened areas,
Slight restrictions
Fusarium IV
Soil A| C
tt
it
n
lorraal
0
Soil A
«
Poor
»t
Reddish streaks
0
Soil B
tt
it
it
Brown roots, black lesions
Fusarium III
Soil C
t»
it
Elongated rotted areas.
Tips black
Fusarium III
Rhizopus
Soil D
tt
tt
Brown roots, black lesions
Fusarium III
Beets
Soil B
n
Excellent
Slight wilting
on one or two
lower leaves
Roots buff coloured.
Crowns dark
Fusarium VII
Fusarium IV
Rhizopus
Broccoli
Soil A
it
Fair
Uormal
Roots badly rotted
Fusarium V
Soil B
it
Good
Crown regions dark
Fusarium V
Fusarium II
Lima Beans
Very poor
it
tt
»
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TABUS I - Ftmgi isolated from root rots of garden crops.
Host
Corn
Location of Host
*Hyde Park
Age of
Plant
Evidence of Root Rot
General
Appearance Appearance of
Appearance of Roots
of Stand
Leaves and Stem
Mature
Crop
harvested
Alternaria inoculated Seedlings Normal
soil*(See Table III
discussion)
Soil A* B
n
H
Celery
Soils A, B, C
n
tt
Lettuce
*London garden
Soils A, B, C
Peas
Organisms
Isolated
Badly rotted
Alternaria sp,
Fusarium VI
n
Generalized rotting
Fusarium III
n
Roots completely destroyed in
two cases out of 10 plants on
A,
Others have lesions
Fusarium V
Normal
Slight yellowing Normal
Mature
It
tt
n
Seedlings
tt
tt
tt
Browned
n
0
Alternaria sp*
Alternaria sp.
Soil A
tt
Very poor
n
it
6 out of 8 have completely
rotted radicles and failed
to reach soil surface
Fusarium IV
Soil C
n
Fair
tt
it
Lesions
Fusarium. IV
Soil I)
m
Poor
Generalized browning
Fusarium IV
Margins of
leaves yellow
Plants wilting
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TABLE I - Fungi isolated from root rots of garden crops.
Host
Location of Host Age of
Plant
Radish
Soil
A,
B
Swiss Chard *London Carden
N.B.
Evidence of Root Rot
General
Appearance of Roots
Appearance Appearance of
of Stand
Leaves and Stem
Seedlings Normal
Mature
tt
Normal
«
Organisms
Isolated
Slight darkening
Fusarium I
Generalized browning with
one or two lesions
Fusarium V
Those marked with an asterisk * indicate that the roots were collected from fields in London
and ■vicinity* All others were obtained from seedlings grown on soils A, B, C, or D in the
greenhouse*
Terminology of Fusarium strains used On the basis of oolour
differences as revealed by culturing on Sherbakoff*s medium.
(see page13).
Fusarium I
1 week old - Pure white, matted hyphae
agar clear
21 days old - as above
Fusarium II
1 week old - Hyphae pale pink*
Growth flocculent.
Substratum immediately beneath streak,
deep rose. By transmitted light,
agar clear,
21 days old - as above
Fusarium III
1 week old - Hyphae white, fluffy, abundant.
Substratum murky yellow by
transmitted light.
21 days old - Substratum pale orange yellow
by transmitted light.
Fusarium IV
1 week old — Hyphae pinkish white. Growth
very fluffy. Substratum clear, except
for white area below mycelium.
21 days old - Substratum deep rose.
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- 21 -
Fusarium V
1 week old
Hyphae pure white* Magenta streaks
on mycelium.
Substratum by trans­
mitted light, rosy pink
21 days old
Substratum becoming a dull blood red.
Fusarium VI
1 week old
Mycelium depressed. Substratum rosy
pink but clear. Color intensity of
substratum darker than in Fusarium YII
21 days old
Substratum deep orange.
Fusarium VII
1 week old
Mycelium fluffy, salmon pink.
Substratum clear, salmon pink.
21 days old
Growth fluffier than in VI.
Substratum identical with YI
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- 22
Results of Pathogenicity fests on sterile seedlings
grown in sterile petri dishes.
Discussion
Table II indicates the result of Inoculation of
healthy sterile roots, under aseptic conditions, with
single spore cultures of the fungi isolated from affected
roots.
The pathogenicity ranges from extreme parasitism in
which 100$ of the plants inooulated became affected, to
mild parasitism in which only 10$ were attacked.
Subsequent experiments with corn inoculated with
Alternaria suggest that Alternarla is probably only a sec­
ondary invader.
(See Discussion of Table III)
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TABLE II - Relative Pathogenicity of Monospore Cultures of Isolants on roots of
seedlings grown from sterile seeds in sterile petri dishes.
—
....------------
Host
Inoculum
Beans fG.W.) Fusarium 17
Humber of Roots Humber of Roots Effect on Roots
Inoculated
Attacked
10
7
lumber of
Re­
isolations
Pathogenicity
Deep lesions. Mycelium abundant
penetrating through to -vascular
cylinder
6
Deep lesions. Tflxole root light
brown
9
+
16
+
+
+
lima Beans
Fusarium III
9
9
Broccoli
Fusarium II
20
16
Fusarium 7
12
2
Slight browning
2
Altemaria gp.
9
1
Root has badly rotted tip
1
Fusarium III
5
5
Rotting severe
3
■f
Fusarium 7
3
3
Slight browning
3
♦
Fusarium 71
16
16
Tips attacked* Lesions wherever
agar is touched, 7ery severe
rotting
9*
♦
3
3
Generalized rot. lot severe
•z
Corn
Lettuce
Alternaria sp.
Slight browning. Tips dark.
One root has severe lesion
* The meagre number of isolations may be explained by the almost instantaneous penetration of E g
rotted roots.
C
Doubtful
lg into severely
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TABLE II - Relative Pathogenicity of Monospore Cultures of Isolants on roots of
seedlings grown from sterile seeds in sterile petri dishes. (Continued)
*
Pathogenicity
Host
Inoculum
Psas
Fusarium IF
8
5
Slight rotting ,
3
♦
Radish
Fusarium I
8
h
Generalized rotting
2
+
Swiss Chard
Fusarium V
5
5
Roots badly rotted
5
+
N.B.
Number of Roots
Inoculated
Number of Roots
Attacked
Effect on Roots
Number of
Re­
isolations
Those forms not producing more than 50% infection under the ideal conditions of the experiment were
designated as slightly pathogenic.
*
Pathogenicity is designated +
pathogenic
2
slightly pathogenic: up to 50?° infection
*
non-pathogenic
- 25 -
Results of Pathogenicity tests on sterile seedlings
grown in inoculated soil
Discussion
Table III summarizes the results obtained from seed­
lings grown in artificially inoculated soil.
The fungi used for inoculum were those previously
isolated from broccoli and corn roots, as indicated in Table I.
The pathogenicity of Alternaria sp. on corn roots is
doubtful.
In both experiments IV and V, fusarium III, as well
as Alternaria. was obtained six times from the most badly
rotted roots,
for example, Alternaria was re-isolated from
the severely attacked tips, while fusarium III was obtained
from the more normal appearing tissue about half an inch back
from the rotted tips.
This suggests the possibility that
invasion of fusarium III may be primary, via the tips; while
the Alternaria attack is secondary*
Evidently the fusarium
strain isolated had been in the roots for a longer period, or
else was a more vigorous parasite since it had progressed
further up the root.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
TABliE III - Relative Pathogenicity of Fungi on Seedlings growing in Sterilized Soil as determined at the end of three weeks*
Host
Inoculum
Source of
Appearance of
Inoculation above-ground parts
Appearance of Roots
l*Broceoli
Fusarium 7
Broccoli
grown on
Soil A
Generalized browning
100
100
100
Hone on 3-weeks
old plants
In all
cases
+
2 ,Brooooli
Fusarium V
Broccoli
grown on
Soil A
Roots light brown, Crown
regions dark. Ho lesions
below crown.
100 ,
100
100
Hone on 3-weeks In all
cases
old plants
♦
26$ of plants
In' all
oases
+
+
3.Com
Fusarium 7
Corn grown
on Soil D
l+.Com
Alternaria sp. Corn from
Hyde Park
5.Com
Altemia sp.
6.Swiss chard Fusarium 7
* Pathogenicity -
Corn from
Hyde Park
Swiss chard
from London
garden
Healthy
!f
Humber; Humber
planted of Roots
Examined
Humber
Effect on Host
of Roots
Attacked
+’
Re­
isolations
Leaves on 9 plants
yellow; in 2 cases
plants wilting
Roots of I4. of these 9
plants have lesions
25
Healthy
Roots badly rotted in
plants up to 1" high. Those
above 1" have constricted
roots in 7 oases
21
21
11
not serious
3
Roots with lesions in 11
Sases Crown susceptible.
Rotting severe in
smallest plants
1+9
1+9
11
not serious
3
Crown and tip region badly
affected. Roots of large
seedlings constricted.
Some roots badly rotted.
50 :
50
50
Ho serious effeci In all
n
11
+
parasitic
£
weakly parasitic up to 25% infection
-
non-parasitic
25
7
affectedj
16% showing
above-ground
symptoms
on above-ground
parts
oases
Patho- *
genicity
- 27 Summary
1*
Of thirteen common garden vegetables examined for
evidence of root rot, four showed no evidence of attack.
These were carrots, celery, parsnips and tomatoes.
2.
The organisms most frequently found were various
strains of Fusarium, one species of Alternaria, and Rhizopua which was apparently a saprophyte.
3*
Seven strains of Fusarium were isolated altogether,
and these were present on all vegetables showing evidence
of root rot, except lettuce which was attacked by Alternaria.
The effect of these on their hosts was as follows;
Fusarium I was slightly pathogenic on radish, but
could not be considered as a serious parasite since the
seedlings were apparently quite vigorous.
Fusarium II caused 80$ infection on broccoli seedling’s
roots without causing any reduction in stand.
Fusarium III was extremely pathogenic causing 100$
infection on lima beans and corn roots.
It was apparently
responsible for the reduction in stand of both vegetables.
Fusarium I? was pathogenic on Golden Wax beans to the
extent of 70$, and on peas to the extent of 62$.
It was
responsible for severe reduction in stand of pea seedlings,
by attacking the radicles almost as soon as they emerged,
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wm
28
Siunmary (oont»d)
and thus reducing the number of seedlings to reach the
soil surface.
Fusarium V was lOOfo pathogenic on corn and Swiss
chard, but only 16$ so on broccoli roots.
Fusarium VI produced 100ft, infection on corn roots
but did not seriously affect the stand in young seedlings.
Alternaria sp* is a very doubtful pathogen on corn
roots, probably being a secondary invader.
However, it
is considerably more pathogenic on lettuce oh'which it
produced 100^ infection*
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- 29 -
Literature Cited
1* Branstetter, B.B. - Corn Boot Hot studies, Univ. of
Missouri Agr. Expt. Sta. Res.
Bui 113. 19272, Burkholder, Walter H. - The Dry Boot - Hot of the Bean.
Cornell Univ. Agr. Exp, Sta.
Memoir 26. 19193, Burrill, T. J,
-
A bacterial disease of Indian corn. Soc.
Prom Agr. Sai, 10th Ann. Proc. pp. 9-27
1889*
Davie, Glen H. and
Chas. S. Reddy - A seedling blight stage
of onion bulb rot (Fusarium sp.) Abstr.
in Phytopath. V 22. 1932.
5. Drechsler, Charles - Two water molds causing tomato rootlet
injury. Jour. Agr. Res. 3^(3)• 1927*
6. Fritz, Clara W. -
Cultural Criteria for the Distinction
of Wood-destroying fungi, p. 201. 1923*
7. Gussow, H. T.
Progress report of the Dominion Botanist.
Gan, Dept. Agr. 1935 - 37•
8. Hansen, H. W.
Etiology of the Pink Root disease of
onions.
9. Harter, L. L.
10. Humphrey, H. B.
Phytopath. V. 19• 1929
Root rot of peas.
Phytopath. V.28. 193®
Studies on the relation of certain species
ffuBerlum to Tomato Blight of the Pacific
Worth West.
State College of Wash. Exp.
Sta. Bui. 115- 191^.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
• - 30 -
IX. Jones, F. R.
-
Stem and root rot of peas in U.S.A.
caused "by species of Fusarium. Jour.
Agr. Res. 7. 26, 1923*
12. Manns, f. F. and C. 1. Phillips - Corn root rot studies.
Jour. Agr. Res. 7. 27. 192*+.
13* Pammel, L. A.
-
Serious root and stalk disease of com.
Iowa Agr. Exp. Sta. Bui. 13. 191^>
14. Rosen, H. R.
-
Bacterial stalk rot of corn. Ark. Agr.
Exp. Sta. Bui. 209. 1926.
13.
Selby, A. D.
- A
brief handbook of diseases of cul­
tivated plants in Ohio. Ohio Agr. Exp.
Sta. Bui. 21^:390, 1910.
16. Smith. E. F.
-
An Introduction to Bacterial Diseases
of Plants. Published by W. B. Saunders
Co., Philadelphia, 1920.
17*
Sherbakoff, C. D. - Fusaria of Potatoes.
Cornell Univ. Agr.
Expt. Sta. Memoir 6, 1915*
15. Taubenhaus. J. J.
Studies on a new Fusarium wilt of
spinach in Texas. Tex. Agr. Exp. Sta'.
Bui. 3I+3, 1926.
19.
"
and Ezekiel
U. S. Dept. Agr. Bur.
Plant Indus., Plant
Disease Reporter 15(6), 1931*
20
»
and F. W. Mally - Pink root disease of onions and its
- control. Ex. Ag. Exp. Sta. Bui. 273* 1921.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
31
21. Valleau, W. D.
- Seed corn infection with PuBarium
moniliforme and its relation to the
root and stalk rots. Ky. Agr. Exp.
Sta. Bui. 226, 1920.
22. Wollemweber, H. ¥.
Studies on the Fusarium problem.
Phytopath 3» 1913*
)
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
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