Transcript 1 - ResearchGate

Control of Root Rot of Sweet Pepper Caused by Phytophthora capsici
with Nonionic Surfactants in a Recirculating Hydroponic System
Enkhjargal Baljii, Won-Seok Na, Jin-Won Kim*
Department of Environmental Horticulture, University of Seoul, Seoul 130-743, Korea
Abstract
Phytophthora capsici is a common and destructive pathogen of pepper crops, especially zoospores of P. capsici spread from inoculated source plants to healthy pepper
plant on the recirculating hydroponic cultural system. In vitro experiments, amending the recirculating nutrient solution with a fungicide (Metalaxyl-M), potassium
phosphonate (KH2PO3) and nonionic surfactants (Tween 20 and Triton X-100) which selectively kill zoospores, and were tested and demonstrated for their control capacity
against P. capsici root rot of sweet pepper (Capsicum annuum cv. New Wave). Sweet peppers were grown in a mini hydroponic system in a greenhouse. Four weeks after the
plants were inoculated with a zoospore suspension of P. capsici, Metalaxyl-M at 0.025 and 0.05 µl/ml treatments showed 65.8% and 77.2% of control value, respectively.
KH2PO3 at 100 and 200 ppm treatments showed 14.3% and 28.6% of control value, respectively. Tween 20 at 500, 1000, 1500, 2000 and 3000 µl/ml treatments showed 0%, 20%,
46%, 88.6% and 94.3% of control value, respectively. Triton X-100 at 250, 500, 1000, 1500 and 2000 µl/ml treatments all showed 100% of control value. The nonionic
surfactants had a direct lytic effect on the zoospores in vitro. The results of this research indicate that nonionic surfactant was potential significance to control sweet pepper
root rot caused by P. capsici in recirculating hydroponic culture.
Introduction


Sweet pepper (Capsicum annuum cv. New Wave) were grown from seed in 240-cellrockwool-plugs in a growth room temperature. Four week-old seedlings were transferred to
mini hydroponic NFT system.
Phytophthora capsici KACC-40158 isolates were obtained from the Korea Agricultural
Culture Collection (Suwon). The stock culture was maintained on potato dextrose agar (PDA)
Petri dish.
Different concentration Metalaxyl-M, potassium phosphonate, nonionic surfactants (Tween
20 and Triton X-100)
In vitro experiment
- Mycelium growth inhibition (Stanghellini and Tomlinson, 1987) .
- Sporangia formation, zoospore release and zoospore lysis [Sporangia and zoospores were
prepared as described by Ristaino (1990)].
- Pathogencity test (seedling symptom test on water agar)
In vivo experiment
- Control effect of caused by P. capsici with Metalaxyl-M, potassium phosphonate, nonionic
surfactants in a recirculating hydroponic NFT system
Disease severity was evaluated after 28 days using a 0-5 scale (Sunwoo et al., 1996).
Control value (%)= [untreated plants (dc) − treated plants (dt) / dc ] x 100
Phytophthora capsici 40158
80
60
40
20
0
1
2
3
4
5
Days after inoculation
Fig. 6. Pathogencity test of Phytophthora capsici. A. Inoculated seedlings, B. Zoosporangium of P. capsici within the root cells
and C. Root intercellular space mycelium
In vivo experiment
DSI
Disease severity (%)

100
Fig. 5. Lytic effect of Triton X-100 on zoospores of
Phytophthora capsici
A. Biflagellate motile
zoospore, B. Granules, and C. Lysis;
CV
100
100
80
80
60
60
40
40
20
20
0
0
Control 0.025
0.05
M.M µl/ml
100
200
500
1000
P.P ppm
1500
2000
3000
250
Tween 20 µl/ml
500
1000
1500
Control value (%)
Material and Methods
Fig. 4. Effect of Metalaxyl-M, Potassium Phosphonate and non ionic
surfactants on sporangium and zoospore production A.Control (water)
B. Fragments of a Phytophthora capsici colony grown on PDA and
placed in sterile water, C-D. Tween-20 500, 3000 µl/ml, E-F. Triton X100 250, 2000 µl/ml, G-H. Metalaxyl-M 0.025, 0.05 µl/ml, I-J. potassium
phosphonate 100, 200ppm
Disease severity (%)
Root rot caused by Phytophthora capsici, is economically important in almost all hydroponic
crops including sweet pepper (Capsicum annuum L.). Symptoms of the disease include root
browning and necrosis, wilting, reduced growth, and decreased yield. Recently, the efficacy of
synthetic surfactant for control of major zoosporic root-infecting pathogens was demonstrated by
Stanghellini and Tomlinson (1987). The objective of this investigation to evaluate the control
efficacy of nonionic surfactants in managing zoosporic plant pathogens in recirculating system.
2000
Triton X-100 µl/ml
Fig. 7. Disease severity and control value four weeks after the plants were inoculated with a zoospore suspension of Phytophthora capsici. Disease
severity index (0-5); 0 = no visible disease symptom, 1 = leaves slightly wilted with brownish lesions beginning to appear on stems, 2 = 30 - 50% of
entire plant diseased, 3 = 50 - 70% of entire plant diseased, 4 = 70 - 90% of entire plant diseased, and 5 = dead plant
In vitro experiment
50
Fw Leaf (g)
Dr Leaf (g)
40
Fw Stem (g)
Dr Stem (g)
Fw Root (g)
Dr Root (g)
5
4
30
3
20
2
10
1
0
0
He*
Di ** 0.025 0.05
Control
M.M µl/ml
100
200
P.P ppm
500
1000 1500 2000 3000
Tween 20 µl/ml
250
500
Dry weight (g/plant)
Fresh weight (g/plant)
Results
1000 1500 2000
Triton X-100 µl/ml
Fig. 8. Fresh weight (FW) and dry weight(DW) four weeks after the plants were inoculated with a zoospore suspension of Phytophthora capsici. Leaf,
stem and roots were separated and oven-dried at 700C for 3 days and dry weights were measured.
* He – health control, ** Di – disease control
Fig. 1. Phytophthora capsici KACC - 40158 A. Colony morphology of PDA
culture medium at 250C, 7 days after, B. Offset sporangiophore, C.
Sporangia papillate and two papilla with long pedicels and lemon type, D.
Medium exit pore, sporangium proliferating from inside an old sporangial
wall, E. Zoospores, F. Encyst, G. Germinating zoospores, and H. Oospore
Fig. 2. Mycelial growth inhibition of Phytophthora capsici A. Control, B-C.
Metalaxyl-M, (0.025 and 0.05 µl/ml), D-E. Potassium phosphonate, (100 and
200ppm), F-J. Tween-20 (500, 1000, 1500, 2000 and 3000 µl/ml), and K-O.
Triton X-100 (250, 500, 1000, 1500 and 2000 µl/ml)
100
MGI (%)
80
60
40
20
0
0.025 0.05 100 200 500 1000 1500 2000 3000 250 500 1000 1500 2000
*
**
M.M µl/ml P.P ppm
Tween 20 µl/ml
Triton X-100 µl/ml
Fig. 3. Effect of different concentration Metalaxyl-M, potassium phosphonate and nonionic surfactants on mycelia growth inhibition
of Phytophthora capsici. Colony radius was measured 3 days after at 25°C. *M.M - Metalaxyl-M, **P.P - potassium phosphonate
Table 1. Effect of different concentration of Metalaxyl-M, potassium phosphonate and nonionic surfactants on sporangium and
zoospore production of Phytophthora capsici z.
Treatment*
Control
0.025
M.M µl/ml
0.05
100
PP ppm
200
500
1000
Tween 20
(µl/ml)
1500
2000
3000
250
500
Triton X-100
1000
(µl/ml)
1500
2000
Sporangia
(no/mm²)
40.9a
1.3bc
0.7c
0.2c
0.1c
2.6b
1.9bc
1bc
1bc
0.3c
0.2c
0c
0c
0c
0c
Zoospore release
(no/ml)
9.6 x 10⁴
0.2 x 10⁴
0.1 x 10⁴
0.0
0.0
1.0 x 10⁴
0.7 x 10⁴
0.1 x 10⁴
0.0
0.0
0.0
0.0
0.0
0.0
0.0
a
d
de
de
de
b
c
de
de
e
e
e
e
e
e
Zoospore lysis
(%)
0
13.6
23.5
31.2
28
81.3
85
84
90.7
96.3
100**
100
100
100
100
number is an average of 10 replicates. Figure with same letter in each column are not significantly different (P=0.05, Duncan’s
range test). *M.M - Metalaxyl-M and P.P - potassium phosphonate; ** All Triton X-100 treatments zoospore lysis in 5 second
Fig. 9. Four weeks after the plants were inoculated with a zoospore suspension of
Phytophthora capsici, A. Health (control) B. Disease (control), C-D. Metalaxyl-M
(0.025 and 0.05 µl/ml), E-F. Potassium phosphonate (100 and 200 ppm), G-K.
Tween 20 (500, 1000, 1500, 2000 and 3000 µl/ml), and L-P. Triton X-100 (250, 500,
1000, 1500 and 2000 µl/ml)
Fig. 10. Four weeks after inoculation root discoloration A. Health
(control), B. Disease (control), C-D. Metalaxyl-M, (0.025 and 0.05
µl/ml), E-F. Potassium phosphonate (100 and 200 ppm), G-K.
Tween-20 (500, 1000,1500, 2000 and 3000 µl/ml), and L-P, Triton
X-100 (250, 500, 1000,1500 and 2000 µl/ml),
Conclusion
The results of this research indicate that nonionic surfactant was potential significance to
control sweet pepper root rot caused by P. capsici in recirculating hydroponic culture.
References
1. Stanghellini, M. E. and Tomlinson, J. A. 1987. Inhibitory and lytic effects of a nonionic surfactant on various asexual stages in the life cycle of Pythium and
Phytophthora species. Phytopathology 77:112-114.
2. Ristaino, J. B, 1990. Intraspecific variation among isolates of Phytophthora capsici from pepper and cucurbit fields in North Carolina. Phytopathology
80:1253-1259.
3. Stanghellini, M. E., Kim, D. H., Rasmussen, S. L. and Rorabaugh, P. A. 1996. Control of root rot of peppers caused by Phytophthora capsici with a nonionic
surfactant. Plant Dis. 80:1113-1116.
4. Sunwoo, J. Y., Lee, Y. K. and Hwang, B. K. 1996. Induced resistance against Phytophthora capsici in pepper plants in response to DL-B-amino-n-butyric
acid. European Journal of Plant Pathology 102: 663-670.
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