Soil-Borne Diseases in Japan - ACS Symposium Series (ACS

Chapter 30

Soil-Borne Diseases in Japan Practical Methods for Biological Control 1

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Shinsaku Hasegawa , Fujio Kodama , and Norio Kondo 1

Hokkaido Institute of Public Health, North 19, West 12, North-ward, Sapporo 060, Japan The Hokkaido Central Agricultural Experiment Station, Naganuma 069-13, Japan

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The interest and research in biological control have increased in this decade. The following are the pro mising procedures which will be adopted in the near future. 1. Sweet potato sprouts which were previously inoculated with non-pathogenic Fusarium oxysporum isolate showed high resistance against Fusarium wilt caused by F. oxysporum f.sp. betatas. 2. Pseudomonas gladioli suppressed some Fusarium diseases. Seedling of associate crops(Allium spp.) which had been dipped in suspension of this strain, and mix-cropped with commercial crops in Fusarium infected field. Fusarium diseases of tomato and bottle gourd(Lagenaria cicereria) were suppressed. 3. Edible lily root rot caused by Cylindrocarpon destructans was controlled when the mother bulbs were coated with P. fluorescens S-2 or P. aeruginosa S-7. These bulbs were much bigger than the non-treated ones. B i o l o g i c a l control of s o i l borne diseases i s keenly being promoted by the government and a g r i c u l t u r a l industries i n Japan. This i s i n part a response to public concern about hazards associated with chemical pesticides. Interest and research on the issue have increased t h i s decade i n Japan. B i o l o g i c a l control has been studied for over 65 years, but few successes have been made i n the commerc i a l f i e l d . The following are the promising a r t i c l e s which w i l l be adopted i n the f i e l d i n near future. The authors discuss three examples of b i o l o g i c a l control of s o i l borne diseases. The f i r s t i s the control of Fusarium w i l t of sweet potato by cross-protection that involves a prior inoculation of nonpathogenic Fusarium oxysporum(Ogawa et al., 1984)(1). The second i s the control of Fusarium w i l t of bottle gourd by mixedcropping with associate crops(Kijima et a l . , 1986)(2). The t h i r d i s the seed bulb bacterization for the control of root rot of edible l i l y ( H a s e g a w a et al., 1990)(3). 0O97-6156/91/0449-O417$O6.00/0 © 1991 American Chemical Society In Naturally Occurring Pest Bioregulators; Hedin, P.; ACS Symposium Series; American Chemical Society: Washington, DC, 1991.

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NATURALLY

OCCURRING PEST BIOREGULATORS


B i o l o g i c a l Control of Fusarium Wilt of Sweet Potato with Crossprotection by Prior Inoculation with Nonpathogenic Fusarium oxysporum The causal fungus of Fusarium w i l t of sweet potato i s Fusarium oxysporum f. sp. betatas. Some i s o l a t e s of F. oxysporum which are obtained from healthy sweet potato plants showed remarkable crossprotection against the disease, when they were previously inoculated in the sweet potato sprouts before being planted i n the infested s o i l . These i s o l a t e s of F. oxysporum were not pathogenic to sweet potato, and also not to other plants such as tomato, cucumber etc. In naturally infested experimental or commercial f i e l d s , crossprotection by pre-inoculation with nonpathogenic i s o l a t e s of F. oxysporum has always brought remarkable decreases i n w i l t incidence and increases i n the y i e l d of sweet potato. The effects were equivalent to those obtained with chemical treatment i n which cutends of the sprouts were dipped into a benomyl suspension(500 times of 50% w.p.) for 30 min., as shown F i g . I.

c CO

rH vO

++^ -°> -° > 2 -°> -° > 6

Phenazine-l-carbox y l i c acid 2 F i g . IV

6

Chlororaphin 3

t r a c e

>

-=

Hemipyocianine

Structure of phenazines.

In Naturally Occurring Pest Bioregulators; Hedin, P.; ACS Symposium Series; American Chemical Society: Washington, DC, 1991.

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Soil-Borne Diseases in Japan

After dipping into the suspension of the biocontrol agent, i . e . s t r a i n S-2, the seed bulbs were transplanted into the f i e l d that was infested with Cylindrocarpon destructans. Table IV shows the e f f e c t of bacterization on the y i e l d of edible l i l y . The growth on the s o i l of the treated plants was obviously higher than the nontreated check. Yields of s t r a i n S-2 and S-7 bulbs treated by dipping were increased 167 and 145%, respectively. Strain S-2 was the most effective with an average bulb weight of 114.6 gm.

Table IV

Effect of bacterization on y i e l d of l i l y


Weight Treatment

Pseudomonas aeruginosa S-7 Pseudomonas fluorescens S-2 Pseudomonas cepacia B-17 Streptomyces sp. B-2 Control

Y

1

^ ? o ?x (kg/4.8m^) 9.6 11.0 7.9 7.1 6.6

b*l a c cd d

o

Length

f

b u l b ( g

o

)

100.9 114.6 85.0 76.7 74.4

f

stem(cm) b a c d d

72.2 68.0 64.5 64.2 64.9

*1 Values within a column followed by the same l e t t e r are not s i g n i f i c a n t l y d i f f e r e n t according to Duncan's multiple range test(P=0.05).

In order to examine whether the antagonist played a role on the roots of the l i l y , we isolated microorganisms from l i l y roots treated with antagonists at harvest time(Table V). The t y p i c a l microflora was recognized. In the plot of s t r a i n S-2, no C. destructance and no Fusarium oxysporum were i s o l a t e d , and the plot of s t r a i n S-7 showed the same indication as s t r a i n S-2. Also, there i s a interesting phenomenon that the number of Trichderma sp. increased i n the plot of strains S-2 and S-7. The antagonists were re-isolated from the treated plants, but not from the non-treated one. The antagonisms exhibited by the treated microorganisms are possibly the result of the production of antifungal agents, which are themselves an e f f e c t i v e protectant against C. destructance. These results indicate that s t r a i n S-2 and s t r a i n S-7 may f a c i l i t a t e establishment of stands of healthy edible l i l y . We assume the mechanism of bacterization by antagonists showed in F i g . V, and expect that two types of e f f e c t s may occur. The f i r s t i s antifungal agents being produced by antagonists at the rhizosphere of plants. We have already isolated and i d e n t i f i e d antifungal agents such as phenazines(Fig. IV), and confirmed that these agents showed strong in vitro antagonistic a b i l i t i e s against Cylindrocarpon destructans(Table III). The other i s the production of growth promoting factors. We have not i d e n t i f i e d the growth promoting substance from strains S-7 and S-2. But, P. cepacia B-17 produced auxin, a t y p i c a l plant growth hormone. These actions are e f f e c t i v e i n protecting against root rot and growing bulbs of edible lily.


NATURALLY OCCURRING PEST BIOREGULATORS

424

Table V

Isolation of microorganisms antagonistic bacteria

from l i l y roots treated with

Treatment


Isolated

Pseudomonas Pseudomonas fluorescens aeruginosa S-2 S-7

microorganism

Fungi Cylindrocarpon destructans Fusarium oxysporum Trichoderma spp. Rhizoctonia solani Pseudomonas spp. Total Pseudomonas spp. Pseudomonas aeruginosa S-7 Pseudomonas fluorescens S-2

15/25 5/25 1/25 2/25

2/25*1 1/25 10/25 0/25

0/25 0/25 16/25 0/25

3.Axl0^ *2 5.0xl0 0

9.3xl0

2

o

Control

4

9

5.0xlO

z

z 1.5xl0 0 0

*1 Number of r o o t l e t s isolated/Number of r o o t l e t s tested. *2 Number of Pseudomonas spp./g of rhizosphere s o i l . Bacterization

No treatment Growth

Growth

A

GROWTH PROMOTING SUBSTANCES

Pseudomonas aeruginosa S-7 Pseudomonas fluorescens S-2 Pseudomonas cepacia B-17

Cylindrocarpon destructans

Fig.

V

ANTIFUNGAL AGENTS

Proposed mechanism of b i o l o g i c a l control of root rot of edible l i l y by Pseudomonas species

Conclusion In Japan, i t i s becoming more and more d i f f i c u l t for growers to achieve satisfactory crop yields using t r a d i t i o n a l b i o l o g i c a l a g r i c u l t u r a l treatments such as crop rotation, t i l l a g e and organic


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Soil-Borne Diseases in Japan

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amendments. On the other hand, chemical control of pests i s often too expensive. That i s the reason why new b i o l o g i c a l control procedures are being keenly demanded. The three types of b i o l o g i c a l control mentioned above w i l l surely be widely applied i n the near future. I t i s true that obviously, much more work remains to be done to c l a r i f y the mechanisms of disease suppression, but successful answers can be obtained from the f i e l d s . The authors w i l l continue to try several approaches, especially the effect of antagonists on edible l i l y root rot b i o l o g i c a l control. Literature Cited


1. 2. 3. 4. 5. 6.

Ogawa, K . ; Komada, H. Ann. Phytopath. Soc. Japan 1984, 50, 1-9. Kijima, T . ; Tezuka, T; A r i e , T; Namba, S; Yamashita, S; Doi, Y Ann. Phytopath. Soc. Japan 1986, 52, 542. Hasegawa, S.; Kondo, N . ; Kodama, F . J . Pharmacobio-Dyn. 1990, 13, i n press. Hasegawa, S.; Kondo, N . ; Kodama, F. Ann. Phytopath. Soc. Japan 1990, i n press. Hasegawa, S.; Kaneshima, H . ; Kodama, F.; Akai, J. Report of the Hokkaido Institute of Public Health 1986, 36, 16-23. Hasegawa, S.; Kondo, N . ; Kodama, F. Naturally Occurring Pest Bioregulators; American Chemical Society: Washington, DC,

RECEIVED July 31, 1990


Soil-Borne Diseases in Japan - ACS Symposium Series (ACS

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