ArticlePDF Available

Efficacy of Different Fungicides and Bio Control Agents Against Fusarium oxysporum, Causal Agent of Potato Dry Rot

Authors:

Abstract and Figures

Objectives: To study the prevalence of potato dry rot in different vegetables markets. To evaluate the effect of Fusarium oxysporum on potato. To study the efficacy of different antagonistic agents and fungicides against mycelia growth of F. oxysporum. Methods/Statistical Analysis: Survey was done from different vegetable markets of Pakistan. Potatoes showing dry rot symptoms were collected and brought to Plant Pathology laboratory. Findings: Antagonistic organisms cause highly significant inhibition in the growth of F. oxysporum which was higher than 60%. Lowest growth of F. oxysporum was found because of an interaction of P. varioti (15.5 mm) and Paecilomyces lilacinus (16.75 mm). Both them cause 82.39% and 80.96% inhibition in the growth of targeted pathogen respectively. Whereas in case of interaction with T. harzianum and Trichoderma polysporum the growth of F. oxysporum was 22.00 mm and 27.75 mm, which is still significantly low as compared to the growth of F. oxysporum 88.00 mm in separate control plates. The growth of pathogen was inhibited by Paecilomyces spp. and mutual inhibition of both antagonist and pathogen at few mm was observed. Whereas, in the case of Trichoderma spp. pathogen and antagonist produce intermingled growth, the growth of the F. oxysporum was ceased and overgrown by antagonist. In-vitro amendment of fungicide in culture media inhibits the colony growth of F. oxysporum. Reduction in colony diameter of F. oxysporum was observed with the application of used antagonistic fungi. Application/ Improvements: These results can be used in the analysis and bio-control methods of Potato dry rot
Content may be subject to copyright.
*Author for correspondence
Indian Journal of Science and Technology, Vol 12(7), DOI: 10.17485/ijst/2019/v12i7/141007, February 2019
ISSN (Print) : 0974-6846
ISSN (Online) : 0974-5645
Ecacy of Dierent Fungicides and Bio Control
Agents Against Fusarium oxysporum,
Causal Agent of Potato Dry Rot
Shehbaz Jawed1, Anum Mehmood2, Arif Hussain2, Zaheer Ahmed Jatoi2,
Aftab Ali Kubar2, Mir Muhammad Nizamani2 and Asif Ali Kaleri3
1Department of Plant Pathology Faculty of Crop Protection, Sindh Agriculture University Tando jam,
Pakistan; shahbazjawed18@gmail.com
2Hainan Key Laboratory for Sustainable Utilization of Tropical Bioresources, Institute of Tropical Agriculture and
Forestry, Hainan University, Haikou, China; gooddranam@yahoo.com, jatoizaheer@gmail.com,
kubar.aftabali@gmail.com, mirmohammadnizamani@outlook.com, hussainarifkaleri@outlook.com
3Department of Agronomy Faculty of Crop Protection, Sindh Agriculture University Tando jam,
Pakistan; asifalikaleri2013@gmail.com
Keywords: Bio-Control, Dry Rot, Fungicides, Fusarium oxysporum, Potato
Abstract
Objectives: To study the prevalence of potato dry rot in different vegetables markets. To evaluate the effect of Fusarium
oxysporum          F.
oxysporum. Methods/Statistical Analysis          
  Findings: Antagonistic organisms
F. oxysporumF. oxysporum
P. varioti (15.5 mm) and Paecilomyces lilacinus
T. harzianum
and Trichoderma polysporumF. oxysporum 
F. oxysporum 
Paecilomyces
TrichodermaF. oxysporum
      F. oxysporum.
Reduction in colony diameter of F. oxysporumApplication/
Improvements:
1. Introduction
Potato (Solanum tuberosum L.) belongs to the family sola-
naceae that includes other 2000 plant species. Tomato
(Lycopersicum esculentum L.), sweet pepper (Capsicum
annuum L.), eggplant (Solanum melongena var. esculentum
L.), tobacco (Nicotiana tabacum L.), and petunia (Petunia
hybrid L.) also belongs to this family. Potato ranks fourth
aer wheat, rice and maize in the list of most important
staple crop of the world.
It is a good source of iron while their vitamin C con-
tents help in iron absorption. Its consumption is increas-
ing because it is not only cheap but also a rich source of
carbohydrates, starch and contributed a lot in the reduc-
tion of food shortage globally1.
Indian Journal of Science and Technology
Vol 12 (7) | February 2019 | www.indjst.org
2
Ecacy of Dierent Fungicides and Bio Control Agents Against Fusarium oxysporum, Causal Agent of Potato Dry Rot
e losses caused by diseases and insects constitute
the major constraints that faced by the potato growers
worldwide. Apart from the eld diseases, postharvest dis-
eases caused considerable economic losses in the quality
and quantity of the produced during transport, storage
and marketing2. Among the diseases the most impor-
tant wide spread and important caused by pathogenic
fungi, aecting tubers and vegetative parts3. A number
of eld and storage disease of potatoes that reduces the
quantity and market value are Black scurf4, Late blight
(Phytophthora infestans)5, Early blight (Alternaria solani)6,
Powdery scab (Spongospora subterrannea)7, Wilt disease
(Verticillium albo-atrum)8, Fusarium dry rot (Fusarium
spp.), Silver scurf (Helminthosporium solani), Gangerene
(Phoma exigua)9, Pink rot (Phytophthora erythroseptica)
and Watery wound rot (Pythium ultimum and P. debarya-
num)10.
One of the main fungal diseases that attack potato is
Fusarium dry rot. is problem persists throughout the
world. ere are many species of Fusarium reported to
cause dry rot of potato worldwide3. Fusarium dry rot
caused by many Fusarium species like F. coeruleum,
F. eumartii, F. oxysporum, F. sulphureum and F. s a m b u-
cinum11. It has been estimated that dry rot caused by
Fusarium spp. caused 6 to 25% yield losses12. Adding to
this yield loss, Fusarium spp. are also well known for the
toxins production in attacked host and responsible for
mycotoxicoses of humans and animals13,14. One of the
toxins produced by the Fusarium spp. which because dry
rots is trichothecene. is toxin is a serious inhibitor of
protein synthesis in prokaryote and can cause serious
health troubles15.
In Turkey, four Fusarium spp. namely F. sambuci-
num, F. s o l ani, F. culmorum and F. oxysporum are found
to be common causes of dry rot of potatoes and have the
potential for complete destruction of potatoes in storage2.
Eighteen percent of tubers arriving at New York markets
from 1972-1980 showed symptoms of Fusarium dry rot16.
While as high as 60% of graded tubers in Scotland was
aected by dry rot17.
Symptoms of Fusarium dry rot include minute brown
areas on the surface of tubers18,19, the infected tubers
appear wrinkled and rolled tissues from the surface, and
rot also creates depressions/ cavity in the surface of the
tuber. ese aected tissues turn brown, grey or black.
When symptoms advances spore masses of blue, white,
yellow, purple, black or pink colour may also observe.
Seed tubers and potatoes for consumption may not com-
pletely. Storage tuber mummies and ultimately only
the dry shell persists20,21. Mode of spread is by planting
infected tubers or by contaminated soil, as the pathogen is
soil borne, airborne or carried in plant residue22.
Biological control of dry rot of potato using dierent
antagonists only evaluated for experimental purposes23.
Antagonistic organisms like Trichoderma spp. and
Pseudomonas aeruginosa have been found to be eective
management strategy24.
Fungicide like Maxim MZ, Tops MZ, and Moncoat
MZ may be used for the ecient control of potato dry
rot. Many chemicals, including iabendazole, may be
applied to seed tubers before sowing25. Continuous use of
same fungicide is the main factor to develop resistance
for it as documented in potato dry rot pathogen against
iabendazole11.
Indiscriminate use of chemical pesticides to control
various pests and pathogenic microorganisms of crops
plants is causing health hazard both in terrestrial and
aquatic lives through their residual toxicity26. Much atten-
tion is being focused on the alternative methods of pest
control27.
Keeping in view the importance of potato dry rot
recent studies carried out to determine the prevalence of
potato dry rot at study area and to evaluate the ecacy
of dierent antagonistic agents and fungicides against F.
oxysporum causal agent of dry rot of potato.
2. Materials and Methods
2.1 Survey and Sampling of Diseased
Specimen
Survey was done from dierent vegetable markets of
Hyderabad region. Potatoes showing dry rot symptoms
were collected and brought to Plant Pathology laboratory.
Incidence of dry rot of potatoes was also recorded with
help of following formula:
( )
100
%
Number of potatoes with dry rot
Incidence Total number of potatoes observed
= ×
2.2 Isolation and Identication of Causal
Fungus
e isolation and identication of fungi was carried out as
described by2 as follows; tubers were washed under run-
ning tap water to remove the mud and then air dried. A 6
Indian Journal of Science and Technology 3
Vol 12 (7) | February 2019 | www.indjst.org
Shehbaz Jawed, Anum Mehmood, Arif Hussain, Zaheer Ahmed Jatoi, Aftab Ali Kubar, Mir Muhammad Nizamani and Asif Ali Kaleri
mm diameter and 5 mm deep pieces were excised with a
cork borer from the aected area of each tuber. e tubers
sections were surface sterilized in 5% commercial bleach
solution for 1 min. Tuber sections were dried on sterilized
paper and plated on Potato Dextrose Agar (PDA). Aer
5 days of incubation at room temperature under natural
light, predominantly isolated fungal colonies developing
from the plant material were identied by microscopic
observations with the help of literature.
Pure culture of fungus was maintained by periodi-
cal transfer on PDA plates. Small colony from corner of
the fungal growth was picked up with help of inoculation
needle and placed on the surface of new freshly prepared
PDA plates. Only one disc transferred per PDA plate and
incubated at 25°C resulting pure culture were multiplied
periodically on new media throughout the study.
2.3 Pathogenicity Test of Causal Pathogen
Pathogenicity test of causal pathogen was carried out for
the conrmation of disease-causing fungus under in-vitro
conditions to prove the Koch’s postulates. e procedure
was performed according to Peters28. e healthy potato
tubers of variety “Diamond” were used in this experi-
ment. Tubers appearing uniform in size (100-120 g) were
selected for this test. First tubers were washed to remove
the surface soil and sterilized by dipping them in 80%
solution of ethanol and then air dried. en the tubers
wounded with a cork borer with adiameter of 5 mm to
a depth of 5 mm28,29. An agar plug (5 mm diameter) con-
taining active growth of F. oxysporum isolates cut from
the margin of a 3-day-old cultures grown on PDA and
placed into the wound, which was subsequently sealed
with the excised plug of tuber tissue. All the wounded
potato tubers were wrapped in polyethylene bags and
incubated in the dark at 20°C for 3 weeks. As acontrol,
tubers were wounded with the help of cork borer like it’s
done in treatment then inoculated with only an agar plug
without fungus. Aer three weeks data were recorded on
the basis of symptoms development and lesion area were
measured in cm with the help of scale.
2.4 Evaluation of Dierent Bio-Control
Agents
Dierent biocontrol agents were obtained From
Agriculture Research Institute, Tandojam to evalu-
ate against Fusarium dry rot of potato by dual cul-
ture method. Briey PDA plates were prepared and
inoculated by F. oxysporum and selected biocontrol agent
aseptically. Both of them were placed at the periphery
of Petri plate at equidistance of 2 to 3 cm in opposite
direction. Petri plates inoculated with pathogen only
served as control. All the plates were incubated at 25°C
in incubators. Plates were observed regularly and data on
colony growth in cm were recorded with the help of scale
and antagonistic nature of the bio agent was recorded.
Resulting data on colony diameter was calculated for
percent inhibition over control with the help of formula
given below:
( )
100
%
CT
Inhibition C
= ×
Whereas, C= Growth of pathogen in control plates;
T=Growth of pathogen in dual culture plates.
After prolonged storage interactions were assessed
using a key based on observations of Dickinson and
Boardman30 as given below:
A. Mutually intermingling growth where both fungi
grew into one another without any microscopic signs
of interaction.
Bi. Intermingling growth where the fungus being
observed was growing into the opposed fungus either
above or below its colony.
Bii. Intermingling growth where the fungus under
observation has ceased growth and is overgrown by
another colony.
C. Slight inhibition where the fungus approach each
other until almost in contact and a narrow demarca-
tion line, 0.1-2 mm, between the two colonies clearly
visible.
D. Mutual inhibition at a distance of > 2 mm.
2.5 Ecacy of Dierent Fungicides
e ecacy of dierent fungicides for controlling F. oxy-
sporum responsible for postharvest infection was car-
ried out with ten dierent fungicides. For this purpose,
Carbendzim, Topsin-M, Mancozeb, Antracol, Gemstar,
Scholar, Nativo, Tilt, Score and Radomil were selected
and evaluated with four dierent doses, i.e., 1 ppm, 10
ppm, 100 ppm, 1000 ppm by food poisoning method
under in-vitro conditions. e details of fungicides with
their company name, active ingredients and brand name
are given in Table 1.
Indian Journal of Science and Technology
Vol 12 (7) | February 2019 | www.indjst.org
4
Ecacy of Dierent Fungicides and Bio Control Agents Against Fusarium oxysporum, Causal Agent of Potato Dry Rot
Concentrations given above were prepared by serial
dilution method. e required quantity of fungicide
was mixed in the medium aer sterilization of media.
Medium without fungicide were served as control. Before
pouring the media were also amended with streptomycin
sulphate at 5 ml/L and penicillin at 106 units/L to avoid
bacterial contamination. Media without fungicide served
as control. Equal volume of media i.e., about 15 ml were
poured in each Petri dish and inoculated in the centre
with a 5 mm disk of F. oxysporum aer solidication
of media. ese plates were incubated as and data were
recorded as described above. Growth was recorded daily
till any of the plate found full of the growth of F. oxyspo-
rum. Finally resulting data was calculated for inhibition
percent because of fungicide with the help of formula as
follows:
( )
100
%
CT
Inhibition C
= ×
Whereas; C = Colony diameter of pathogen in con-
trol plates; T = Colony diameter of pathogen in plates
amended with fungicide (treatment plate).
3. Results
3.1 Prevalence of Potato Dry Rot
Potatoes showing dry rot symptoms were collected from
dierent markets (Figure 1). Hundred potatoes were ran-
domly examined from each store. e disease found to
prevail in 70% of the stored visited with a very low inci-
dence. Average disease incidences of dry rot of potatoes
were recorded 3.4%. e isolation and identication
of fungi was carried out by tissue isolation methods.
Isolations were made with aected potatoes. Total 100
sections were placed over the surface of PDA medium.
Aer incubation of 5 days at 25°C fungal colonies iden-
tied by microscopic observations with the help of
literature as Fusarium spp. and Aspergillus spp. F. oxys-
porum was appeared as most predominant fungus with
59% frequency (Table 2). Pure cultures of F. oxysporum
were maintained on PDA medium and were multiplied
periodically on new media throughout the study. On
PDA medium it produced white aerial mycelia became
tinged with light purple. From backside of plates dark
purple and produces abounded micro and macro conidia,
Microconidia were oval to ellipsoid cylindrical while
macroconidia long fusoid to falcate in shape with 3 or 4
septa (Figure 2). ese morphological characteristics are
similar those described19,31.
Table 1. List of the fungicides used in the experiments
Brand Name Company Name Active ingredient
Topsin-M Arysta iophanate Methyl 70 WP
Mancozeb FMC Dithiocarbamates 75% WP
Antracol Bayer Propineb 70% WP
Carbendazim Clear Carbendazim 50 WP
Ridomil Sygenta Metaxyl 68 WP
Score Sygenta Dinaconazole 250 EC
Tilt Sygenta Propiconazole 250 EC
Nativo Bayer (Tebuconazole+Trioxystobin)75WG
Scholar Sygenta Fludioxonil 230 SC
Gemstar Sun Crop Azoxystrobin 250 EC
Figure 1. Potato tubers showing dry rot disease
symptoms.
Indian Journal of Science and Technology 5
Vol 12 (7) | February 2019 | www.indjst.org
Shehbaz Jawed, Anum Mehmood, Arif Hussain, Zaheer Ahmed Jatoi, Aftab Ali Kubar, Mir Muhammad Nizamani and Asif Ali Kaleri
ve dierent doses, i.e., 1, 10, 100, 1000 and 10000 ppm
by Food poisoning method. All concentrations of fungi-
cides reduced the growth of F. oxysporum as compared to
control. However, higher concentrations were more eec-
tive than the lower ones. e growth of the test pathogen
gradually decreased with increasing concentrations. All
the fungicide at 10000 ppm completely stops the growth
of test pathogen.
Score (63.80 mm), followed by Carbendazim (69.33
mm), Gemstar (70.5 mm) and Mancozeb (70.80 mm) at
produces the lowest growth as compare to other fungi-
cides at the same dose. Topsin-M, followed by Scholar and
Score at 10 ppm produces 29.16 mm, 45.66 mm and 53.83
mm respectively, aer seven days of incubation at 28°C as
compared to the 89.66 mm growth at control. Topsin-M
(9.83 mm and 2.16 mm) followed by Mancozeb (21.50
mm and 5.33 mm) and Scholar (25.00 mm and 6.00 mm)
produces lowest growth respectively at 100 and 100 ppm
as compare to other fungicide at the same dose (Figure 4).
IC50 values for each fungicide were also calculated.
It greatly varied for each fungicide. Lowest IC50 value
was found in case of Topsin-M, Scholar, Antracol and
Radomil i.e., 8.65 ppm, 16.99 ppm, 36.45 ppm and 46.89
ppm, respectively. Whereas, highest IC50 value was found
in Nativo followed by Tilt and Gemstar i.e., 240.36, 206.32
and 109.96, respectively (Figure 5 and 6).
3.3 Eect of Dierent Bio-Control Agents on
the Growth of F. oxysporum
Four dierent bio-control agents i.e. Paecilomyces lilaci-
nus, Trichoderma harzianum, T. polysporum and P. varioti
were obtained from ARI Tandojam and evaluated against
3.2 Pathogenicity Test F. oxysporum on
Potato Tubers
Pathogenicity test of F. oxysporum was carried out for the
conrmation of disease-causing fungus under in-vitro
conditions to prove the Koch’s postulates. Aer 3-week
incubation, the inoculated potatoes showed wrinkled and
rotted symptoms of typical dry rot of potato. e rotted
areas of the potatoes were brown, grey, or black and the
rot creates depressions in the surface of the tuber. White
fungal growth was also apparent on rotted areas. Lesion
area aer 20 days of inoculation was extended up to
27.10mm.
Very small lesion were also found to develop in un-
inoculated control potatoes (1.8 mm), where tubers were
wounded with the help of corn borer like it’s done in
treatment then inoculated with only an agar plug without
fungus (Figure 3).
Eect of dierent fungicides on colony growth of F. oxy-
sporum:
e ecacy of dierent fungicides against the col-
ony growth of F. oxysporum was checked under labora-
tory conditions. For this purpose, Radomil, Topsin-M,
Antracol, Mancozeb, Carbendzim, Score, Tilt, Scholar,
Nativo, and Gemstar, were selected and evaluated with
Figure 2. Growth of F. oxysporum isolated from potato
tubers having dry rot of potato disease on PDA and macro
and micro conidia under 400X magnication of compound
microscope.
Table 2. Disease incidences of potato dry rot collected
from 10 dierent vegetables market of Hyderabad regions
and frequency of isolated fungi
Incidences (%) = (34/1000) *100
3.4 %
Frequency of isolated fungi
Fusarium oxysporum (58%)
Another Fusarium spp. (30%)
Aspergillus spp. (22%)
Figure 3. Eect of articial inoculation of F. oxysporum
on lesion development. Data was recorded aer 22 days of
incubation at 25°C.
Indian Journal of Science and Technology
Vol 12 (7) | February 2019 | www.indjst.org
6
Ecacy of Dierent Fungicides and Bio Control Agents Against Fusarium oxysporum, Causal Agent of Potato Dry Rot
Figure 4. Eect of dierent concentrations of various fungicides on the colony growth of the F. oxysporum. Bar with
dierent letters show signicant dierence (P≤0.05) as determined by LSD.
Figure 5. IC50 value of Radomil, Topsin-M, Antracol, Mancozeb, Carbendzim and Score against F. Oxysporum.
Indian Journal of Science and Technology 7
Vol 12 (7) | February 2019 | www.indjst.org
Shehbaz Jawed, Anum Mehmood, Arif Hussain, Zaheer Ahmed Jatoi, Aftab Ali Kubar, Mir Muhammad Nizamani and Asif Ali Kaleri
Figure 6. IC50 value of Tilt, Scholar, Nativo and Gemstar against F. Oxysporum.
F. oxysporum by dual culture method. Both of them were
placed at the periphery of Petri plate at equidistance in
opposite direction. All four antagonistic organisms cause
highly signicant inhibition in the growth of F. oxyspo-
rum which was higher than 60%. Lowest growth of F.
oxysporum was found as a result of interaction of P. v a r i-
oti (15.5 mm) and P. lilacinus (16.75 mm). Both of them
cause 82.39% and 80.96% inhibition in the growth of tar-
geted pathogen, respectively. Whereas in case of interac-
tion with T. harzianum and T. polysporum the growth of
F. oxysporum was 22.00 mm and 27.75 mm, which is still
signicantly low as compare to the growth of F. oxysporum
88.00 mm in separate control plates. T. harzianum and T.
polysporum cause 75.00% and 68.46% inhibition in the
growth of F. oxysporum (Figure 7). Antagonistic nature
of the bio-agents was recorded with prolonged incuba-
tion. Both specie Paecilomyces of shows D type interac-
tion i.e. mutual inhibition of both at a distance of few mm
while Trichoderma spp. shows Bii type interaction i.e., F.
oxysporum and Trichoderma spp. produces intermingled
growth; growth of the F. oxysporum was ceased and over-
grown by antagonist (Figure 8).
4. Discussion
Dry rot potato is one of the main fungal pathogens that
attack potato throughout the world. e disease found to
Figure 7. Eect of Paecilomyces varioti, Trichoderma
polysporum, T. harzianum and P. lilacinus on the growth/
inhibition of F. oxysporum. Bar with dierent letters show
signicant dierence (P≤0.05) as determined by LSD.
Indian Journal of Science and Technology
Vol 12 (7) | February 2019 | www.indjst.org
8
Ecacy of Dierent Fungicides and Bio Control Agents Against Fusarium oxysporum, Causal Agent of Potato Dry Rot
prevail in 70% of the stored visited in Hyderabad region
with a very low incidence. Average disease incidences of
dry rot of potatoes were recorded 3.4%. It has been esti-
mated dry rot caused by Fusarium spp. causes 6% to 25%
yield losses12.
Symptoms of Fusarium dry rot include minute brown
areas on the surface of tubers18, the infected tubers appear
wrinkled and rolled tissues from the surface, and rot also
creates depressions/cavity in the surface of the tuber.
ese aected tissues turn brown, grey or black. When
symptoms advances spore masses of blue, white, yellow,
purple, black or pink colour may also observe.
Seed tubers and potatoes for consumption may rot
completely. Storage tuber mummies and ultimately only
the dry shell persists14,20,21.
e isolation from diseases tissues revealed the asso-
ciation of Fusarium spp. and Aspergillus spp. F. oxyspo-
rum was appeared as most predominant fungus. ere
are many species of Fusarium reported to cause dry rot
of potato worldwide3. Fusrium dry rot caused by many
Fusarium species like F. coeruleum, F. eumartii, F. oxy-
sporum, F. sulphureum and F. sambucinum Fuckel11.
Mejdoub-Trabelsi24 isolated four Fusarium spp. predomi-
nantly associated with dry rot of potato. i.e., F. s a m bu-
cinum, F. oxysporum, F. sol a n i and F. graminearum. On
PDA medium it produced morphological characteristic
that are similar those described by19,31.
Pathogenicity test of F. oxysporum conrmed the
virulent nature of the pathogen and produces the similar
symptoms of potato dry rot. Author in32 conrmed the
pathogenicity of two F. oxysporum isolates associated
with potato dry rot in Colombia. Inoculation with both
induced moderate dry rot. Mode of spread is by planting
infected tubers or by contaminated, as the pathogen is soil
borne, airborne or carried in plant residue22. erefore,
emphasis must be given to control dry rot of potato. So
far, this disease is managed with the application of fun-
gicides.
Continuous use of same fungicide is the main fac-
tor to develop resistance for it as documented in potato
dry rot pathogen against iabendazole11. erefore, in
present study dierent fungicide determined against F.
oxysporum causal agent of dry rot of potato. Radomil,
Topsin-M, Antracol, Mancozeb, Carbendzim, Score, Tilt,
Scholar, Nativo, and Gemstar, were selected and evaluated
with ve dierent doses, i.e., 1, 10, 100, 1000 and 10000
ppm by food poisoning method. All concentrations of
fungicides reduced the growth of F. oxysporum as com-
pared to control. However, higher concentrations were
more eective than the lower ones. e growth of the test
pathogen gradually decreased with increasing concentra-
tions. All the fungicide at 10000 ppm completely stops the
growth of test pathogen. Similarly, Piwoni33 found sixty
isolates of F. avenaceum and forty isolates of F. coeruleum
sensitive to used fungicide, while eighty-ve isolates of
sixty eight percent ofF. sulphureumand one isolate ofF.
culmorum were found not sensitive to iabendazole.All
A
B
C
Figure 8. Eect of dierent biocontrol fungi on the
growth/inhibition of F. oxysporum A=Paecilomyces varioti;
B=Trichoderma harzianum and C= T. Polysporum.
Indian Journal of Science and Technology 9
Vol 12 (7) | February 2019 | www.indjst.org
Shehbaz Jawed, Anum Mehmood, Arif Hussain, Zaheer Ahmed Jatoi, Aftab Ali Kubar, Mir Muhammad Nizamani and Asif Ali Kaleri
the Fusarium spp. were sensitive to Imazalil and were
pathogenic when inoculated into potato tubers. Yasmin34
also found Azoxystrobin, Quinoline, Hymexazol and
Fludioxonil with inhibitory eect on mycelial growth of
F.oxysporumf. sp.tuberosi.
IC50 values for each fungicide were also calculated. It
greatly varied for each fungicide. Lowest IC50 value was
found in case of Topsin-M, Scholar, Antracol and Radomil.
Whereas, highest IC50 value was found in Nativo followed35
tested six fungicides; Carbendazim, Benomyl, Prochloraz,
Azoxystrobin, Fludioxonil and Bromuconazole, against F.
oxysporum f. sp. lycopersici with seven dierent concentra-
tions. Prochloraz and Bromuconazole were the most eec-
tive fungicides against the pathogen both in vitro and in
vivo, followed by Benomyl and Carbendazim. Fungal radial
growth was measured and median eective concentration
(EC50) values (µg/ml) determined. Biological controls
of dry rot with dierent bio-control agents such as fungi,
bacteria, and yeasts have been reported as eective under
experimental conditions23,36. Four dierent bio-control
agent’s i.e., Paecilomyces lilacinus, P. varioti, Trichoderma
harzianum and T. polysporum. All four antagonistic organ-
isms cause highly signicant inhibition in the growth of
F. oxysporum which was higher than 60%. Antagonistic
organisms like Trichoderma spp. and Pseudomonas aeru-
ginosa have been found to be eective management strat-
egy24. Author in34 found reduction in colony diameter of F.
oxysporum isolated from potato dry rot by T. harzianum, T.
viride and T. virens.
Antagonistic nature of the bio-agents was recorded
with prolonged incubation. Growth of pathogen was
inhibited by Paecilomyces spp. and mutual inhibition of
both antagonist and pathogen at a distance of few mm was
observed. Whereas in case of Trichoderma spp. pathogen
and antagonist produces intermingled growth, growth of
the F. oxysporum was ceased and overgrown by antago-
nist. Similar interaction was also reported37. Author in34
evaluated dierent Trichoderma spp. against F. oxysporum
isolate from potato dry rot i.e., T. harzianum, T. viride
and T. virens and studied interaction mechanisms which
include disintegration of host cytoplasm and/or alteration
into cords and/or coiling around pathogen hyphae.
5. Summary
Dry rot is considered the most important post-harvest
disease that attack potato throughout the world especially
for seed production where are store for prolonged dura-
tion. e disease found to prevail in 70% of the stored
visited in Hyderabad region with very low incidences.
Average disease incidences of dry rot of potatoes were
recorded 3.4%. Symptoms of Fusarium dry rot include
minute brown areas on the surface of tubers. e infected
tubers appear wrinkled and rolled tissues from the sur-
face, rot also creates depressions/ cavity in the surface
of the tuber. ese aected tissues turn brown, grey or
black. When symptoms advance fungal spore masses of
varying colour may also observed. e isolation from
diseases tissues revealed the association of Fusarium spp.
and Aspergillus spp. F. oxysporum was appeared as most
predominant fungus. Pathogenicity test of F. oxysporum
conrmed the virulent nature of the pathogen and pro-
duces the similar symptoms of potato dry rot.
So far, this disease is managed with the application of
fungicides. Continuous use of same fungicide is the main
factor to develop resistance for it as documented in potato
dry rot pathogen against iabendazole. In present study,
dierent fungicides were tested against causal agent of
dry rot of potato. Ten fungicide i.e., Radomil, Topsin-M,
Antracol, Mancozeb, Carbendzim, Score, Tilt, Scholar,
Nativo, and Gemstar, were evaluated against F. oxysporum
with ve dierent doses, i.e., 1, 10, 100, 1000 and 10000
ppm by food poisoning method. All concentrations of
fungicides reduced the growth of F. oxysporum as com-
pared to control. However, higher concentrations were
more eective than the lower ones. e growth of the test
pathogen gradually decreased with increasing concentra-
tions. All the fungicide at 10000 ppm completely stops
the growth of test pathogen. IC50 value for each fungi-
cide was also calculated from fungal radial growth at ve
dierent concentrations. It greatly varied for each fungi-
cide. Lowest IC50 value was found in case of Topsin-M,
Scholar, Antracol and Radomil. Whereas, highest IC50
value was found in Nativo followed.
Four dierent bio-control agents’ i.e., Paecilomyces
lilacinus, P. varioti, Trichoderma harzianum and T. polys-
porum. All four antagonistic organisms cause highly sig-
nicant inhibition in the growth of F. oxysporum which
was higher than sixty percent. Antagonistic nature of
the bio-agents was recorded with prolonged incubation.
Growth of pathogen was inhibited by Paecilomyces spp.
and mutual inhibition of both antagonist and pathogen
at a distance of few mm was observed. Whereas in case
of Trichoderma spp. pathogen and antagonist produces
Indian Journal of Science and Technology
Vol 12 (7) | February 2019 | www.indjst.org
10
Ecacy of Dierent Fungicides and Bio Control Agents Against Fusarium oxysporum, Causal Agent of Potato Dry Rot
intermingled growth, growth of the F. oxysporum was
ceased and overgrown by antagonist.
6. Conclusions
Prevalence of potato dry rot in Hyderabad, Sindh, ecacy
of dierent antagonistic agents and fungicides against F.
oxysporum causal agent of dry rot of potato are studied.
Dierent Fusarium spp. and Aspergillus spp. were found
associated with the collected potatoes with varying fre-
quencies. F. oxysporum was appeared as most predomi-
nant isolated fungus with the maximum frequency of
59%. Typical symptoms of dry rot of potato appeared on
articially inoculated tubers with F. oxysporum. Fungal
fruiting bodies also appeared on rotted areas aer pro-
longed storage.
In vitro fungal growth test in the presence of dierent
fungicide were performed in order to nd out best fungi-
cide. Ten fungicides viz., Radomil, Topsin-M, Antracol,
Mancozeb, Carbendzim, Score, Tilt, Scholar, Nativo and
Gemstar were evaluated against F. oxysporum with ve
dierent doses, i.e., 1, 10, 100, 1000 and 10000 ppm by
food poisoning method. Fungal diameter in the Petri
dishes was recorded every day till any of the treatment
nd full of fugal growth. All concentrations of fungicides
reduced the growth of F. oxysporum as compared to con-
trol. However, higher concentrations were more eec-
tive than the lower ones. e growth of the test pathogen
gradually decreased with increasing concentrations. All
the fungicide at 10000 ppm completely stops the growth
of test pathogen.
IC50 value for each fungicide was also calculated
from fungal radial growth at ve dierent concentra-
tions, it greatly varied for each fungicide. Lowest IC50
value was found in case of Topsin-M, Scholar, Antracol
and Radomil. Whereas, highest IC50 value was found in
Nativo followed.
Four dierent bio-control agents i.e. Paecilomyces
lilacinus, P. varioti, Trichoderma harzianum and T. polys-
porum were tested against dry rot pathogen. All four
antagonistic organisms cause highly signicant inhi-
bition in the growth of F. oxysporum which was higher
than sixty percent. Growth of pathogen was inhibited by
Paecilomyces spp. and mutual inhibition of both antago-
nist and pathogen at few mm was observed. Whereas in
case of Trichoderma spp. pathogen and antagonist pro-
duces intermingled growth, growth of the F. oxysporum
was ceased and overgrown by antagonist.
7. Recommendation
e results of the present study shows that dry rot of
potato prevail in study area but with low incidences.
However, to reduce the present incidences and to reduce
the further spread management methods should be eval-
uated. In-vitro amendment of fungicide in culture media
inhibits the colony growth of F. oxysporum. erefore
in-vivo application of fungicide for the control of this
disease should be evaluated. Reduction in colony diam-
eter of F. oxysporum was observed with the application of
used antagonistic fungi. In this connection further stud-
ies should be carried out to nd out the alternative of fun-
gicide for management of this disease.
8. References
1. Oerke EC. Crop losses to pests. e Journal of Agricultural
Science. 2006; 144(1):31–43. https://doi.org/10.1017/
S0021859605005708
2. Introduction. e Identication of Fungi: An Illustrated
Introduction with Keys, Glossary, and Guide to Literature.
Available from: https://www.amazon.in/Identication-
Fungi-Illustrated-Introduction-Literature/dp/0890543364
3. Lucas JA. Fungi, food crops, and biosecurity: Advances and
challenges. Advances in Food Security and Sustainability.
2017; 2:1–40. https://doi.org/10.1016/bs.af2s.2017.09.007
4. Yang F, Min W, Wang Q, Wei M, Guo Y, Gao X, Dong,
Lu D. Anastomosis group and pathogenicity of rhizoc-
tonia solani associated with stem canker and black scurf
of potato in Heilongjiang Province of China. American
Journal of Potato Research. 2017; 94(2):95–104. https://doi.
org/10.1007/s12230-016-9535-3
5. Goutam U, akur K, Salaria N, Kukreja S. Recent
approaches for late blight disease management of potato
caused by phytophthora infestans. Fungi and their Role in
Sustainable Development: Current Perspectives; 2018. p.
311–25. https://doi.org/10.1007/978-981-13-0393-7_18
6. Mazáková J, Zouhar M, Sedlák P, Zusková E, Ryšánek P,
Hausvater E. Sensitivity to fungicides and esential oils
in Czech isolates of phytophthora infestans. Scientia
Agriculturae Bohemica. 2018; 49(2):69–77. https://doi.
org/10.2478/sab-2018-0011
7. Lin CY, Ni HF, Huang CW. First report of common scab on
potato caused by streptomyces europaeiscabiei in Taiwan.
Plant Disease. 2018; 102(4):1–818. https://doi.org/10.1094/
PDIS-05-17-0667-PDN
8. Fusarium wilt: A killer disease of lentil. Available from:
https://www.intechopen.com/books/fusarium-plant-dis-
eases-pathogen-diversity-genetic-diversity-resistance-and-
molecular-markers/fusarium-wilt-a-killer-disease-of-lentil
Indian Journal of Science and Technology 11
Vol 12 (7) | February 2019 | www.indjst.org
Shehbaz Jawed, Anum Mehmood, Arif Hussain, Zaheer Ahmed Jatoi, Aftab Ali Kubar, Mir Muhammad Nizamani and Asif Ali Kaleri
9. Garibaldi A, Gilardi G, Minerdi D, Gullino ML. First report
of leaf spot caused by Phoma exigua on hydrangea macro-
phylla in Italy. Plant Disease. 2006; 90(8):1–1113. https://
doi.org/10.1094/PD-90-1113B
10. Liu Y, Hu CH, Wang CY, Xiong Y, Li ZK, Xiao C. Occurrence
of parthenogenesis in potato tuber moth. Journal of Insect
Science. 2018; 18(1):1–14. https://doi.org/10.1093/jisesa/
iey003
11. Hanson L. Sensitivity to iabendazole in Fusarium species
associated with dry rot of potato. Phytopathology. 1996;
86(4):1–378. https://doi.org/10.1094/Phyto-86-378
12. Fusarium species complex causing Pokkah Boeng in
China. Available from: https://www.intechopen.com/
books/fusarium-plant-diseases-pathogen-diversity-
genetic-diversity-resistance-and-molecular-markers/
fusarium-species-complex-causing-pokkah-boeng-in-china
13. Maeda K. Studies on Fusarium trichothecene biosynthe-
sis: functional characterization of orthologous pathway
genes and development of various types of inhibitors. JSM
Mycotoxins. 2018; 68(2):77–82. https://doi.org/10.2520/
myco.68-2-1
14. Ding ZL, Wu JP, Yang CZ, Zhou J, Jiao ZB, Guo FL. First
Report of Fusarium meridionale and Fusarium incarnatum
Causing Dry Rot of Konjac in China. Plant Disease. 2018;
102(1):1–247. https://doi.org/10.1094/PDIS-06-17-0931-PDN
15. Bammidi K, Dandnayak B. Survey for the incidence of
fusarium wilt of coriander in Latur, Osmanabad and
Beed Districts of Maharastra. International Journal
of Plant and Soil Science. 2018; 23(2):1–5. https://doi.
org/10.9734/IJPSS/2018/42513 https://doi.org/10.9734/
IJPSS/2018/43130
16. Dua VK, Rawal S, Singh S, Sharma J. Improving potato cul-
tivation practices: An overview. Burleigh Dodds Series in
Agricultural Science; 2018. p. 23–43.
17. Osawa H, Akino S, Araki H, Asano K, Kondo N. Eects
of harvest injuries on storage rot of potato tubers infected
with Phytophthora infestans. European Journal of Plant
Pathology. 2018; 152(2):561–5. https://doi.org/10.1007/
s10658-018-1498-4
18. Struik PC. Understanding ageing processes in seed pota-
toes. Burleigh Dodds Series in Agricultural Science. 2015;
8:33–55.
19. Srivastava S, Kadooka C, Uchida JY. Fusarium species as
pathogen on orchids. Microbiological Research. 2018;
207:188–95. https://doi.org/10.1016/j.micres.2017.12.002
PMid:29458853
20. Dubey K, Singh SK. Study cultural, morphological and
pathogenic variation among dierent isolates of Fusarium
oxysporum f. sp. lentis. International Journal of Current
Microbiology and Applied Sciences. 2018; 7(9):170–5.
https://doi.org/10.20546/ijcmas.2018.709.021
21. Pettis GS. Mechanisms of pathogenicity and emergence of
new plant-pathogenic species in the genus streptomyces.
Virulence Mechanisms of Plant-Pathogenic Bacteria; 2016.
p. 445–56. https://doi.org/10.1094/9780890544495.023
22. Hoitink HAJ, Locke JC. An integrated approach to
biological control of fusarium species in container-
ized crops. Fusarium Wilts of Greenhouse Vegetable
and Ornamental Crops; 2017. p. 109–15. https://doi.
org/10.1094/9780890544822.013
23. Gadgile D. Post-harvest fungal diseases of guava: A brief
review. International Journal of Processing and Post Harvest
Technology. 2017; 8(1):56–8. https://doi.org/10.15740/
HAS/IJPPHT/8.1/56-58
24. Mejdoub-Trabelsi B, Ben Abdallah RA. Assessment of the
antifungal activity of non-pathogenic potato associated
fungi toward fusarium species causing tuber dry rot dis-
ease. Journal of Plant Pathology and Microbiology. 2016;
7(4):1–114. https://doi.org/10.4172/2157-7471.1000343
25. Hay WT, Fanta GF, Rich JO, Schisler DA, Selling GW.
Antifungal activity of a fatty ammonium chloride amy-
lose inclusion complex against Fusarium sambucinum;
Control of dry rot on multiple potato varieties. American
Journal of Potato Research. 2019; 96(1):79–85. https://doi.
org/10.1007/s12230-018-9683-8
26. Fothergill A, Abdelghani A. A review of pesticide residue
levels and their related health exposure risks. Food and
Environment II. 2013; 170:1–11. https://doi.org/10.2495/
FENV130181
27. Vander Zaag P. Toward sustainable potato production: expe-
rience with alternative methods of pest and disease control
on a commercial potato farm. American Journal of Potato
Research. 2010; 87(5):428–33. https://doi.org/10.1007/
s12230-010-9161-4
28. Peters JC, Lees AK, Cullen DW, Sullivan L, Stroud GP,
Cunnington AC. Characterization of Fusarium spp. respon-
sible for causing dry rot of potato in Great Britain. Plant
Pathology. 2008; 57(2):262–71. https://doi.org/10.1111/
j.1365-3059.2007.01777.x
29. Choiseul J, Allen L, Carnegie SF. Fungi causing dry tuber rots
of seed potatoes in storage in scotland. Potato Research. 2007;
49(4):241–53. https://doi.org/10.1007/s11540-007-9020-y
30. Dickinson CH, Boardman F. Physiological studies of
some fungi isolated from peat. Transactions of the British
Mycological Society. 1970; 55(2):293–305. https://doi.
org/10.1016/S0007-1536(70)80014-6
31. Pathogenic and morphological variability among
Fusarium oxysporum f. sp. ciceri isolates causing wilt in
chickpea. Available from: https://www.researchgate.net/
publication/326737978_Pathogenic_and_morphologi-
cal_variability_among_Fusarium_oxysporum_f_sp_cic-
eri_isolates_causing_wilt_in_chickpea
Indian Journal of Science and Technology
Vol 12 (7) | February 2019 | www.indjst.org
12
Ecacy of Dierent Fungicides and Bio Control Agents Against Fusarium oxysporum, Causal Agent of Potato Dry Rot
32. Bayona LG, Grajales A, Cárdenas ME, Sierra R, Lozano G,
Garavito MF, Cepero de García MC, Bernal A, Jiménez P,
Restrepo S. Isolation and characterization of two strains of
Fusarium oxysporum causing potato dry rot in Solanum
tuberosum in Colombia. Revista Iberoamericana de
Micología. 2011; 28(4):166–72. https://doi.org/10.1016/j.
riam.2011.03.007 PMid:21635960
33. Piwoni A. Pathogenicity of Fusarium avenaceum isolates to
tulip leaves assessed on leaf disks. Acta Agrobotanica. 2013;
55(1):265–9. https://doi.org/10.5586/aa.2002.025
34. Yasmin L, Ali M, Khan F. Ecacy of fungicides in con-
trolling fusarium wilt of gladiolus. Bangladesh Journal of
Agricultural Research, 2018; 42(4):599–607. https://doi.
org/10.3329/bjar.v42i4.35787
35. eradimani M, Susitha S, Amudha C. Biocontrol of
Fusarium Wilt in Tomato caused by Fusarium oxyspo-
rum f. sp. lycopersici. International Journal of Current
Microbiology and Applied Sciences. 2018; 7(9):420–9.
https://doi.org/10.20546/ijcmas.2018.709.052
36. Singh D, Sharma RR. Postharvest diseases of fruits and
vegetables and their management. Postharvest Disinfection
of Fruits and Vegetables; 2018. p. 1–52. https://doi.
org/10.1016/B978-0-12-812698-1.00001-7
37. Spader TB, Venturini TP, Cavalheiro AS, Mahl CD, Mario
DN, Lara VM, Alves SH. In vitro interactions between
amphotericin B and other antifungal agents and rifampin
against Fusarium spp. Mycoses. 2011; 54(2):131–6. https://
doi.org/10.1111/j.1439-0507.2009.01773.x PMid:19780977
Article
Bromuconazole, a fungicide from the triazole family, is widely used to protect the crop from various fungal contaminations to increase product quality and productivity. Although the massive use of bromuconazole poses a serious risk to human health, the exact mechanism of bromuconazole toxicity, especially on brain support cells, called glia cells, remains unclear so far. This study aimed to determine the mechanism of cytotoxicity and genotoxicity of bromuconazole via inspection of apoptotic death in rat glioma (F98) cells. We observed that bromuconazole treatment caused concentration-dependent cell death with an IC50 of 60 µM, and disruption of the cytoskeleton was observed via immunocytochemical analysis. Further, bromuconazole inhibits cell proliferation, it arrests the cell cycle in the G0/G1 phase and so inhibits DNA synthesis. Genotoxic analysis showed that bromuconazole exposition causes DNA fragmentation (comet assay) and nuclear condensation (DAPI staining). Apoptotic cell death was confirmed through: positive Annexin-V/FITC-PI dyes, p53 and Bax overexpression, Bcl2 repression, an increase in Bax/BCL-2 ratios of the mRNA, mitochondrial membrane depolarization, and an increase of caspase-3 activity. All these results demonstrate that bromuconazole exerts its cytotoxic and genotoxic effects through apoptotic cell death, which could implicate mitochondria.
Article
Dry rot caused by Fusarium spp. is a devastating disease of potato, which occurs frequently around the world and causes significant economic losses. Chemical fungicides are the main strategy for dry rot prevention and control, but their intensive and long-term use can easily lead to fungal resistance, toxic residues, and environmental pollution, etc. Herein, safe and sustainable biological control is gradually becoming the hotspot and has a broad application prospect. Microorganisms and bioactive substances should be the important elements of biocontrol, which can inhibit the growth of Fusarium or induce potato resistance to resist dry rot. This review focuses on the pathogenic fungi, biocontrol microorganisms, bioactive substances and their biocontrol mechanisms of potato dry rot, in order to provide a theoretical basis for further research and application on biological control of the disease.
Article
Full-text available
A total of 235 Phytophthora infestans isolates were collected from five regions of the Czech Republic during the growing seasons 2012–2014 and 2016 and examined using the in vitro amended agar method for their sensitivity to metalaxyl-M (MFX), propamocarb-HCl (PCH), and dimethomorph (DMM). A majority of the isolates (50%) were sensitive to MFX. Resistant isolates were found in all four years of the survey; they represented 30% of the samples. The EC50 values of PCH in inhibiting mycelial growth of 65% of the overall isolates were higher than 100 µg ml–1, which indicates the occurrence of insensitivity to PCH in the Czech P. infestans populations. DMM was very effective, and the mycelial growth of all isolates tested was completely suppressed at the concentration of 0.1 µg ml–1. Furthermore, the efficacy of 12 plant essential oils was tested against 20 isolates of P. infestans using the in vitro amended agar method. Essential oils of Cymbopogon winterianus, Litsea cubeba, Mentha spicata, Pelargonium graveolens, Syzygium aromaticum, and Thymus vulgaris were observed to have the highest antifungal activity against P. infestans, with minimal inhibitory concentrations less than or equal to 1 µl ml–1.
Article
The cationic amylose-hexadecylammonium chloride inclusion complex (Hex-Am) was found to be an effective antifungal treatment for Fusarium sambucinum (Fückel), a causal agent of potato dry rot. The Hex-Am treatment was effective against F. sambucinum in vitro and in situ, with an effective 50% inhibitory concentration of 400 μg/ml; active component concentration of 20 μg/ml. The amylose complex alone, and blended with polyvinyl alcohol (PVOH), was effective in controlling dry rot in five varieties of potatoes with up to a 99% reduction in damage to the potato tubers. The amylose complex showed no apparent signs of phytotoxicity, with wound periderm reforming within one week of storage at 15 °C and 90% RH. The Hex-Am treatments form an effective antimicrobial film at the wound site, significantly inhibiting fungal damage to the wounded tubers.
Chapter
Potato (Solanum tuberosum) is the fourth most produced noncereal crop worldwide. Among various biotic stresses, late blight caused by Phytophthora infestans is the most devastating disease. It affects both potato foliage in the field and tuber in the storage which can absolutely destroy a crop, producing a 100% crop loss. The occurrence and rigorousness of late blight caused by Phytophthora can be reduced by adopting effective and durable control methods. The use of conventional control methods (cultural practices and fungicides) was limited due to their inefficiency and non-biodegradable nature. Control of the disease has been achieved up to a great extent through the use of fungicides, but their extensive application is harmful for the environment. Therefore, there is an urgent need to find alternative eco-friendly crop protection methods. The use of microorganisms as biological control agents owing to their different modes of actions (i.e. antagonistic effects or induction of plant defence mechanisms) has proved to be a potential approach. Another economical and eco-friendly remedial measure for plant diseases being adopted involves the use of nanoparticles against plant pathogens. Providing genetic resistance against pests and diseases is another crop protection approach. Multiple resistance (R) genes have been introduced in potato varieties to provide durable resistance to late blight. Genetic modification using cisgenes is preferable as it is a feasible and highly efficient approach with low risks and high societal acceptability. Accumulation of new virulent P. infestans strains decreases the effectiveness of R-genes. Therefore, the loss of function in susceptible gene via gene silencing is the emerging approach which helps in exploring plant-pathogen interactions and provides potential strategies for disease control. RNA silencing without altering the plant genome overcomes the risk associated with transgenic plants.
Article
We explored the effects of harvest damage on potatoes infected with Phytophthora infestans in 2015 and 2016. Injured tubers were inoculated with zoosporangia suspensions and incubated at 18°C in the dark for 4 weeks. In 2015 and 2016, 38.5% and 74.4%, respectively, of injured tubers inoculated with P. infestans rotted and hyphal masses were apparent on the tuber surfaces. Tubers in the uninjured group rarely rotted even when there were numerous P. infestans zoosporangia on the inoculated tuber surface. The percentage of rotten tubers in the injured/no inoculation group caused by other types of fungi or bacteria increased rapidly, to approximately 20% within one week; however, there was very little increase during the subsequent incubation. Conversely, the percentage of rotten tubers increased with incubation time in the injured/inoculation group and this phenomenon was significant in 2015. These results imply that not only the presence of P. infestans but also surface harvest injuries affect potato storage rot. Storage rot can be minimized by reducing surface injuries and/or decreasing blighted plant material and the population density of P. infestans in the soil at the time of harvest during commercial potato production.
Article
Characterization of trichothecene hydroxylation enzymes and screening of trichothecene production inhibitors were performed to decrease the frequency of false detection and reduce grain contamination by trichothecene mycotoxins. Molecular genetic studies of trichothecene biosynthetic genes revealed that the trichothecene C-4 hydroxylase, FgTRI13p, encoded by FgTri13 of Fusarium graminearum, has co-evolved with the C-7/C-8 hydroxylase, FgTRI1p, encoded by FgTri1. FgTRI13p shows highly restricted substrate specificity for trichothecene intermediates compared with FsTRI13p produced by Fusarium sporotrichioides. A glutamine analog, acivicin, was screened as an inhibitor of trichothecene production from the chemical library of the RIKEN Natural Products Depository. The predicted mode of action of acivicin in F. graminearum was that the acivicin-induced nutrient starvation repressed the trichothecene master regulator encoded by FgTri6, which blocked trichothecene production. In addition, another trichothecene production inhibitor NPD352 [testosterone 3-(O-carboxymethyl)oxime amide-bonded to phenylalanine methyl ester] was obtained from the library by chemical array screening using trichodiene synthase (FgTRI5p) as a target protein. The mixed-type inhibitor NPD352 may bind and interfere with intracellular FgTRI5p under conditions favoring trichothecene production.