• Journal of Food Hygiene and Safety
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• v.37 no.1
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• pp.9-14
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• 2022

The purpose of this study was to analyze the hazard of fungi in Garaetteok (Korean rice cake) by isolating and identifying of fungi contaminated with Garaetteok and investigating the possibility of mycotoxin production. Garaetteok used in this study were the ones that were returned back to the manufacturers in Jeollanam-do due to the presence of foreign matters presumed to be fungi. The fungi foreign matter was collected and inoculated on Potato dextrose agar, Malt extract agar, and Czapek yeast extract agar, and then cultured at 25℃ for 7 days. The micro-structure was observed under an optical microscope for the colonies in which pure isolation was confirmed. The gene sequencing of the product of amplified PCR was analyzed using the ITS primer. Colony-1 and 2 maintained the same properties in each tray, confirming that they were purely isolated. Budding cells were observed from the Colony-1, thus, it was determined to be yeast. Colony-2 was determined to be a fungus that belongs to Fusarium spp. as fusiform conidia were observed. As a result of gene sequencing, a total of 76 cases of fungi of Fusarium spp. were found, among which Fusarium solani was the most observed cases (53 cases). From the morphological and genetic identification, Colony-2 was identified as Fusarium spp., specifically, Fusarium solani. The fungi found in Fusarium spp. produce mycotoxins such as nivalenol, zearalenone, and fumonisin, which may cause vomiting, diarrhea, and cancer. Conclusively, the results confirm the possibility of mycotoxin production by Fusarium spp. isolated from Garaetteok. Consequently, when an unknown fungus was found, it is necessary to isolate and identify the fungus, determine whether it is a mycotoxin producing species, and strengthen relative administrative measures, accordingly.

• Horticultural Science & Technology
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• v.33 no.3
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• pp.409-419
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• 2015

This study was conducted to establish an efficient screening method for watermelon plants resistant to Fusarium wilt (FW), which is caused by Fusarium oxysporum f. sp. niveum (Fon). An HA isolate was prepared from a wilted watermelon plant in Haman-gun and identified as F. oxysporum f. sp. niveum based on morphological characteristics, molecular analyses of ITS (internal transcribed spacer) and TEF (translation elongation factor $1{\alpha}$) sequences, and host specificity on cucurbits including watermelon, melon, oriental melon, and cucumber. The assay for disease response of watermelon differentials indicated that the HA isolate was race 0. Among seven liquid media tested, the highest amount of Fon spores was produced from V8-juice broth, which was selected as a medium for mass production of Fon. The disease assay for 21 watermelon and 11 watermelon-rootstock cultivars demonstrated that 20 watermelon cultivars except for 'Soknoranggul' were susceptible; 'Soknoranggul' was moderately resistant. All the tested rootstock cultivars were highly resistant to the HA isolate. The evaluation of disease development depending on various conditions suggested that an efficient screening method for FW resistance in watermelon plants is to dip the roots of 10-day-old seedlings in spore suspension of $1.0{\times}10^5-1.0{\times}10^6conidia{\cdot}mL^{-1}$ for 30 min., to transplant the seedlings to plastic pots with a fertilized soil, and then to cultivate the plants at $25^{\circ}C$ for 3 weeks.

• Horticultural Science & Technology
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• v.33 no.1
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• pp.70-82
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• 2015

This study was conducted to establish an efficient screening system to identify melon resistant to Fusarium oxysporum f. sp. melonis. F. oyxsporum f. sp. melonis GR was isolated from infected melon plants collected at Goryeong and identified as F. oxysporum f. sp. melonis based on morphological characteristics, molecular analyses, and host-specificity tests on cucurbits including melon, oriental melon, cucumber, and watermelon. In addition, the GR isolate was determined as race 1 based on resistance responses of melon differentials to the fungus. To select optimized medium for mass production of inoculum of F. oxysporum f. sp. melonis GR, six media were tested. The fungus produced the most spores (microconidia) in V8-juice broth. Resistance degrees to the GR isolate of 22 commercial melon cultivars and 6 rootstocks for melon plants were investigated. All tested rootstocks showed no symptoms of Fusarium wilt. Among the tested melon cultivars, only three cultivars were susceptible and the other cultivars displayed moderate to high resistance to the GR isolate. For further study, six melon cultivars (Redqueen, Summercool, Superseji, Asiapapaya, Eolukpapaya, and Asiahwanggeum) showing different degrees of resistance to the fungus were selected. The development of Fusarium wilt on the cultivars was tested according to several conditions such as plant growth stage, root wounding, dipping period of roots in spore suspension, inoculum concentration, and incubation temperature to develop the disease. On the basis of the test results, we suggest that an efficient screening method for melon plants resistant to F. oxysporum f. sp. melonis is to remove soil from roots of seven-day-old melon seedlings, to dip the seedlings without cutting in s pore s uspension of $3{\times}10^5conidia/mL$ for 30 min, to transplant the inoculated seedlings to plastic pots with horticulture nursery media, and then to cultivate the plants in a growth room at 25 to $28^{\circ}C$ for about 3 weeks with 12-hour light per day.

• The Korean Journal of Mycology
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• v.27 no.2 s.89
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• pp.87-93
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• 1999

This study was conducted to investigate the morphological characteristics and cultural conditions for artificial fruiting body(synnemata) production of Paecilomyces japonica. In the morphological characteristics of P. japonica, the size of it's conidia was ranged from $5.0{\sim}1.5\;to\;7.9{\sim}2.4\;{\mu}m$. The artificial fruiting body showed yellow in color, shape was confirmed ellipsoidal or obovoid type, and the length was $50.6{\sim}104.5\;mm$. The mycelial growth on the PDA medium treated with pH7, at $25^{\circ}C$ was superior to that of other treatments. The formation period of an artificial fruiting body of P. japonica treated with polypropylene and glass bottle culture was 30 days and 50 days, respectively. The length and number of fruiting body was longer and higher in the polypropylene bottle culture than those of the glass bottle culture. As the results, the artificial fruiting body production in the polypropylene bottle increased 1.2g per bottle compared to that of the glass bottle. It also increased in $100{\sim}400\;lx$ illumination, whereas the elongation of synnemata, pinheading and fruiting body growth were inhibited by continuous use of 900 lx illumination. The results of these experiment indicated that fruiting body formation seemed to be lower as the light intensity increased. The fruiting body formation was also dependent on the light color. There was a higher incidence in red color light and fluorescent light treatment than that of incandescent and blue color light. The fruiting body of the naked barley medium had so much better growth compared to other media that it would be able to use for it's production. The growth of fruiting body was affected by $CO_2$ concentration. It increased after putting the lid on the bottle.

• The Korean Journal of Mycology
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• v.25 no.2 s.81
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• pp.143-151
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• 1997

Interspecific hybrids between Aspergillus niger and Penicillium notatum (Tyr-), hyperlipolytic enzyme-producing fungi, were obtained by nuclear transfer technique. Optimal conditions for formation of intergeneric hybrids were investigated. Maximum production of protoplasts was obtained by 1% Novozyme 234 at $30^{\circ}C$ for 3 hrs and the most effective osmotic stabilizers for the isolation of protoplasts were 0.6 M KCl. Frequencies of hybrid formation by nuclear transfer were $3.8{\times}10^{-3}{\sim}1.3{\times}10^{-3}$. From the observation of genetic stability, conidial size, DNA content, and nuclear stain, it was suggested that their karyotypes are aneuploid. The hybrids showed $1.2{\sim}1.7$ fold higher lipase activities than parental strains. It was strongly supported by results of this study that nuclear transfer technique is much more efficient in the formation of intergeneric hybrids than protoplast fusion and is very useful for the improvement of strains.

• Microbiology and Biotechnology Letters
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• v.35 no.2
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• pp.128-134
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• 2007

Previously, we isolated plant growth promoting rhizobacterium (PGPR) Bacillus licheniformis K11 which could produce auxin, cellulase and siderophore. The siderophore of B. licheniformis K11 $(siderophore_{K11})$ was determined to be a catechol type siderophore which is produced generally by Bacillus spp. B. licheniformis K11 could produce the siderophore most highly after 96 h of incubation under nutrient broth at $20^{\circ}C$ with initial pH 9.0. For the production of the $siderophore_{K11}$, trehalose and $NH_4Cl$ were the best carbon and nitrogen sources in Davis minimal medium, respectively. The $siderophore_{K11}$ was Produced in M9 medium (pH 9.0) after 4 days at $20^{\circ}C$, and purified from culture broth of B. licheniformis K11 by using Amberlite XAD-2, Sephadex LH-20 column chromatography, and reversed-phase HPLC. The $siderophore_{K11}$ had the biocontrol activity against spore germination of P. capsici and F. oxysporum on potato dextrose agar (PDA). The results indicate that the $siderophore_{K11}$ is an antifungal mechanism of B. licheniformis K11 against phytopathogenic fungi.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.65 no.1
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• pp.30-39
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• 2020

A new silicate coating technology was developed which reduces the impact of dust and loosening during seeding compared to existing silicate-coatings (Seed/Si/Zeolite), and therefore can lower the production costs of rice cultivation. In this method, 100 g of rice seed is coated with 18 mL of liquid silicic acid and then dressed with a mixture containing 80 g of dolomite and 5 g of iron. To determine the most effective method of application and ensure that seedlings developed healthily, a series of experiments were carried out. Infected seeds scattered in seedling boxes and pots (soil and hydroponic) were coated dry, without disinfection. In comparison to the seed which were not treated with the silicate-coating, the new seed (A) were 1.84 times heavier in weight, and were also improved in terms of coating strength and coating color. Compared to the seedlings grown from the non-coated seed, those grown from the new silicate-coated seed were of significantly higher quality (weight/length) and had erect, dark greenish leaves, which are ideal plant characteristics. This was most likely due to increased silicate uptake. The symptoms of bakanae disease in the non-coated seed peaked after 38 days to 54.2%, whereas the control value was 68.8% in the new silicate-coated seed (A). In the infected seedlings grown from the new silicate-coated rice seed, subnormal macro-conidia, namely, a sickle shape spore without a septum; a straight oblong shape spore without a septum and with a thick cell wall; and inter-septal necrosis of a normal spore were detected. It is believed that the strong alkalinity of silicic acid have acted as unfavorable conditions for pathogenicity. In seedlings grown from the new silicate coated rice seed under hydroponic conditions without nutrients, normal root activity and growth was maintained without leaf senescence. Therefore, it was possible to reduce the rate of fertilization. In the future, a new silicate-coated rice seed was required for the study of minimal nutrition for anti-aging of seedlings.