• The Plant Pathology Journal
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• v.27 no.4
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• pp.390-395
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• 2011

Fusarium wilt caused by Fusarium oxysporum has become a serious problem world-wide and relies heavily on chemical fungicides. We selected Pseudomonas sp. NJ134 to develop an effective biocontrol strategy. This strain shows strong antagonistic activity against F. oxysporum. Biochemical analyses of ethyl-acetate extracts of NJ134 culture filtrates showed that 2,4-diacetylphloroglucinol (DAPG) was the major compound inhibiting in vitro growth of F. oxysporum. DAPG production was greatly enhanced in the NJ134 strain by adding mannitol to the growth media, and in vitro antagonistic activity against F. oxysporum increased. Bioformulations developed from growth of NJ134 in sterile bean media with mannitol as the carbon source under plastic bags resulted in effective biocontrol efficacy against Fusarium wilt. The efficacy of the bioformulated product depended on the carbon source and dose. Mannitol amendment in the bean-based formulation showed strong effective biocontrol against tomato Fusarium wilt through increased DAPG levels and a higher cell density compared to that in a glucose-amended formulation. These results suggest that this bioformulated product could be a new effective biocontrol system to control Fusarium wilt in the field.

• 한국균학회소식:학술대회논문집
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• 2018.05a
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• pp.41-41
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• 2018

There has been an impetus in the development of biocontrol agents (BCAs) with the removal of a number of chemical compounds in the market, especially in the European Union. This has been a major driver in the development of Integrated Pest Management systems (IPM) for both pest and disease control. For control of mycotoxigenic fungi, there is interest in both control of colonization and more importantly toxin contamination of staple food commodities. Thus the relative inoculum potential of biocontrol agent vs the toxigenic specie sis important. The major bottlenecks in the production and development of formulations of biocontrol agents are the resilience of the strains, inoculum quality and formulation with effective field efficacy. It was recently been shown for mycotoxigenic fungi such as Aspergillus flavus, under extreme climate change conditions, growth is not affected although there may be a stimulation of aflatoxin production. Thus, the development of resilient biocontrol strains which can may have conserved control efficacy but have the necessary resilience becomes critical form a food security point of view. Indeed, under predicted climate change scenarios the diversity of pests and fungal diseases are expected to have profound impacts on food security. Thus, when examining the identification of potential biocontrol strains, production and formulation it is critical that the resilience to CC environmental factors are included and quantified. The problems in relation to the physiological competence and the relative humidity range over which efficacy can occur, especially pre-harvest may be increase under climate change conditions. We have examined the efficacy of atoxigenic strains of A. flavus and Clanostachys rosea and other candidates for control of A. flavus and aflatoxin contamination of maize, and for Fusarium verticillioides and fumonisin toxin control. We have also examined the potential use of fluidized-bed drying, nanoparticles/nanospheres and encapsulation approaches to enhance the potential for the production of resilient biocontrol formulations. The objective being the delivery of biocontrol efficacy under extreme interacting climatic conditions. The potential impact of climate change factors on the efficacy of biocontrol of fungal diseases and mycotoxins are discussed.

• The Plant Pathology Journal
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• v.21 no.1
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• pp.59-63
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• 2005

Bacillus subtilis S1-0210 was selected as a biological agent against Botrytis cinerea in strawberry. The isolate inhibited mycelial growth of B. cinerea in vitro tests. A wettable powder formulation of B. subtilis S1-0210 significantly reduced infection rates with lower than 5%, compared with higher than 70% of infection rates in untreated control. The formulation showed 85 to 89% control efficacies of gray mold incidences on fruits of strawberry in pots. Pre-treatment of the agent was more effective in controlling gray mold on fruits and leaves than post-treatment at the early stage of disease development. The formulation also showed 70% control efficacy of gray mold incidence on fruits of strawberry in a field trial. The results indicate that B. subtilis S1-0210 in the wettable powder formulation may be a potential biocontrol agent to control gray mold on strawberry.

• Research in Plant Disease
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• v.21 no.3
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• pp.222-226
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• 2015

The chitinase-producing bacterial strain C-1 is one of the key chitinase-producing biocontrol agents used for effective bioformulations for biological control. These bioformulations are mixed cultures of various chitinolytic bacteria. However, the precise identification, biocontrol activity, and the underlying mechanisms of the strain C-1 have not been investigated so far. Therefore, we evaluated in planta biocontrol efficacies of C-1 and determined the draft genome sequence of the strain in this study. The bacterial C-1 strain was identified as a novel Serratia sp. by a phylogenic analysis of its 16S rRNA sequence. The Serratia sp. C-1 bacterial cultures showed strong in planta biocontrol efficacies against some major phytopathogenic fungal diseases. The draft genome sequence of Serratia sp. C-1 indicated that the C-1 strain is a novel strain harboring a subset of genes that may be involved in its biocontrol activities.

• Proceedings of the Korean Society of Plant Pathology Conference
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• 2003.10a
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• pp.97.2-98
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• 2003

A new and effective formulation using antagonistic bacteria, Burkholderia cepacia YC5025 in vegetable oil was developed for the biocontrol of anthracnose. The bacterial population in the formulation was maintained to 5x10/sup7/ cfu/ml upto 60 days at room temperature. Control efficacy of the formulation for anthracnose was over 80％ by spraying of diluted suspension(x1,000) in growth chamber tests. On the contrary, the bacterial suspension in distilled water or bacterial culture broth containing same number of spores as the formulation had low control efficacy around 40％ even 2-weeks storage after preparation. The shelf-life of the formulation was longer than that of bacterial preparation using clay minerals such as talc or bentonite. The mechanisms of newly developed bacterial formulation are possibly the formation of water film on the surface of cucumber leaves and inactivation of the bacteria in the vegetable oils during storage. Further field tests and improvements with new liquid bacteiral formulation need to be done for practical application.

• The Plant Pathology Journal
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• v.19 no.3
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• pp.129-132
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• 2003

Fusarium wilt of cucumber caused by Fusarium oxy-sporum f. sp. cucumerinum is a serious vascular disease worldwide. Biological control of Fusarium wilt in several crops has been accomplished by introducing non-pathogenic Fusarium sup. and other biocontrol agents in soil or in infection courts. In this study, quantitative models were used to determine the biocontrol efficacy of inundatively applied antagonist formulations and the length of their effectiveness in controlling Fusarium wilt of cucumber. Quantitative model of the form [Y=L (1${-exp}^{-kx}$)] best described the relationship between disease incidence (Y, %) and inoculum density (X) of isolates F51 and F55. Isolate F51 was selected as a more virulent isolate based on the extent of its effectiveness in causing the wilt disease. The degree of disease control (Xi/X) obtained with the density of the biocontrol agent (Z), was described by the model [Xi/X=A (1${-exp}^{-cz}$)]. The zeolite-based antagonist formulation amended with chitosan (ZAC) was better at lower rates of application and peaked at around 5 g/ kg of the potting medium, whereas the peat-based antagonist formulation (PA) peaked at around 10 g/kg of the potting medium. ZAC formulation provided significantly better suppression of Fusarium wilt as described by the curvilinear relationship of the type Y= a+bX+c$X^2$, where Y represents percent disease incidence and X represents sustaining effect of the biocontrol agent.

• The Plant Pathology Journal
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• v.21 no.4
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• pp.328-333
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• 2005

Paenibacillus elgii SD17 (KCTC $10016BP^T$=NBRC $100335^T$) was recently reported as a new species. Based on its inhibitory activity to Thanatephorus cucumeris AG1-1, strain SD17 was further evaluated for its potential as a biocontrol agent against soil-borne diseases of turf grasses in Korea. P. elgii SD17 showed a broad spectrum of antimicrobial activity in vitro test and suppressed development of turf grass diseases; Pythium blight caused by Pythium aphanidermatum and brown patch caused by T. cucumeris AG1-1 on creeping bentgrass (Agrostis palustris) in the growth chamber tests. Under a condition for massive culture in a 5,000 L fermenter, P. elgii SD17 reached $6.4{\times}10^8$ spores/ml that resulted in approximately $1.0{\times}10^7$ cfu/g when formulated into a granule formulation (GR) using the whole culture broth instead of water. Using the GR formulation, biocontrol activity of P. elgii SD17 was confirmed. In the growth chamber tests, the GR formulation was effective against brown patch and Pythium blight with similar level of disease severity compared to each of the standard fungicides at the application rates of 10 g/$m^2$ or above. In the field tests, compared to each untreated control, the GR formulation also effectively controlled Pythium blight, brown patch and large patch at all the application rates of 5, 10 and 20 g/$m^2$, respectively, without significant response by the application rates. However its performance was inferior to each of the standard chemical fungicides. Based on these results, we consider this GR formulation of P. elgii SD17 as an effective biocontol agent to suppress Pythium blight, brown patch and large patch of turf grasses in Korea.

• Proceedings of the Korean Society of Plant Pathology Conference
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• 2003.10a
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• pp.98.1-98
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• 2003

Antagonistic effect of bacterial strains isolated from phylloplane of strawberry plants grown In greenhouse was tested on Botrytis cinerea Among the promising bacterial strains, Bacillus sp. S1-0210 showed highest inhibition of mycelial growth of B. cinerea and a broad spectrum of antifungal activities against many plant pathogenic fungi in vitro. Bacillus sp. S1-0210 was identified as Bacillus subtilis based on the analysis of 185 rDNA as well as its biochemical characteristics. Application of wettable powder formulation of B. subtiiis S1-0210 significantly reduced the incidence of gray mold on trawberry fruits during storage. Results showed that treatment of B. subtilis S1-0210 decreased the incidence of gray mold by 4.8％ whereas the incidence in control was 77.9％, indicating that the formulation of B. subtilis S1-0210 will be practically applied on strawberry fruits as a biocontrol agent of gray mold during storage.

• Proceedings of the Korean Society of Life Science Conference
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• 2007.10a
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• pp.105.2-105.2
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• 2007

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• The Plant Pathology Journal
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• v.18 no.1
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• pp.30-35
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• 2002

The hyphal growth and biocontrol efficacy of Trichodemo harzianum in soil may depend on its interactions with biotic components of the soil environment. The effect of soil microbial biomass on growth and biocontrol efficacy of T. hanianum isolate ThzIDl-M3 (green fluorescent protein transformant) was investigated using artificially prepared different levels of soil microbial biomass (153,328, or 517ug biomass carbon per g of dry soil; BC). The hyphal growth of T. harzanum was significantly inhibited in the soil with 328 or 517 $\mu$g BC compared with 153 ug BC. When ThzIDl-M3 was added to the soils as an alginate pellet formulation, the recoverable population of ThzIDl-M3 varied, but the highest population occurred in 517ug BC. Addition of alginate pellets of ThzIDl-M3 to the soils (10 per 50 g) resulted in increased indigenous microbial populations (total fungi, bacterial fluorescent Pseudomonas app., and actinomycetes). Furthermore, colonizing ability of ThzIDl-M3 on sclerotia of Sclerotinia sclerotiorum was significantly reduced in the soil with high revel of BC. These results suggest that increased soil microbial biomass contributes to increased interactions between introduced T. harzianum and soil microorganisms, consequently reducing the biocontrol efficacy of 1T. harzianum.