• Journal of Microbiology and Biotechnology
• /
• v.19 no.3
• /
• pp.314-322
• /
• 2009

Four different bacterial colonies were isolated from an old stock of an entomopathogenic nematode, Steinernema monticolum. They all showed entomopathogenicity to final instar larvae of beet armyworm, Spodoptera exigua, by hemocoelic injection. However, they varied in colony form, susceptibility to antibiotics, and postmortem change of the infected host insects. Biolog microbial identification and 16S rDNA sequence analyses indicate that these are four different species classified into different bacterial genera. Owing to high entomopathogenicity and a cadaver color of infected insect host, Serratia sp. was selected as a main symbiotic bacterial species and analyzed for its pathogenicity. Although no virulence of Serratia sp. was detected at oral administration, the bacteria gave significant synergistic pathogenicity to fifth instar S. exigua when it was treated along with a spore-forming entomopathogenic bacterium, Bacillus thuringiensis. The synergistic effect was explained by an immunosuppressive effect of Serratia sp. by its high cytotoxic effect on hemocytes of S. exigua, because Serratia sp. caused septicemia of S. exigua when the bacterial cells were injected into S. exigua hemocoel. The cytotoxic factor(s) was present in the culture medium because the sterilized culture broth possessed high potency in the cytotoxicity, which was specific to granular cells and plasmatocytes, two main immune-associated hemocytes in insects.

• The Korean Journal of Mycology
• /
• v.27 no.1 s.88
• /
• pp.66-67
• /
• 1999

Neozygites fresenii (Zygomycetes: Entomophthorales), aphid-attacking fungus, was found in June 1998 for the first time in Korea. The fungus produces the globose primary conidia with a truncate papillar and two types of the secondary conidiophores and conidia. Resting spores were not found in our specimens, but the fungal structures observed clearly distinguish the fungus from other aphid-attacking fungi, allowing inclusion in the species N. fresenii.

• International Journal of Industrial Entomology and Biomaterials
• /
• v.9 no.2
• /
• pp.229-234
• /
• 2004

Six entomopathogenic fungus isolates, Beauveria bassiana J57A, Nomuraea rileyi J125A, Paecilomyces farinosus J3A, Paecilomyces fumosoroseus J50A, Metarhizium anisopliae J88, Aspergilius sp. J64A, causing muscardine disease and aspergillosis in the silkworm, Bombyx mori were investigated for their cultural and morphological characteristics (on PDA culture media within 14 days at $24^{\circ}C$). The results showed that they differ each other from the features of cultural characteristics (colony elevation, colony color, colony growth rate) or morphological characteristics (conidiogenous cell structure, phialides, conidia size and shape). Among cultural characteristics, colony color is the easiest recognizable character between isolates. The morphological characteristics of each fungal isolate correspond to the descriptions of current system of classification.

• The Korean Journal of Mycology
• /
• v.28 no.2
• /
• pp.112-117
• /
• 2000

A similarity coefficient were analyzed by RFLP of fourteen species of entomopathogenic fungi, isolated from inhabiting pupa and adult insect at forest. Each rDNA ITS I and ITS II with primers of ITS 1 and ITS 4 was amplified by PCR. The amplified products were conserved to 500 bp were not demarcated between genus and species. Four Paeciliomyces tenuipes, two Beauveria bassiana and six Cordyceps militaris were treated by seven restriction enzymes and confirmed in species except JB3 by electrophoresis band. However, the band of C. scarabaeicola showed the identity with B. bassiana. The result of this experiment indicated that the teleomorph of C. scarabaeicola was the same as that of B. bassiana. CfoI and HpaII of seven restricted enzymes were easily discriminating in the genus between Paecilomyees and Cordyceps. Especially, CfoI was more effective to classify the genera of Paecilomyees, Cordyceps and Beauveria than other restriction enzymes. The band patterns of RFLP of P. tenuipes, C. militaris, C. scarabaeicola and B. bassiana were also analyzed by UPGMA program of NTSYS-pc and showed 100% significance. Thus, the similarity coefficient tended to be lower between genera by RFLP analysis, but was higher between species.

• Korean journal of applied entomology
• /
• v.40 no.3
• /
• pp.259-264
• /
• 2001

Toxicological studies of two potential biological control agents, the entomopathogenic nematode (Steinernema carpocapsae) and the symbiotic bacteria (Xenorhabdus nematophilus) were conducted against two beneficial insects and one mammal species. Two microbial agents varied in their toxicities between two insect species: an ant, Pristomyrmex pungens, and silkworm, Bombyx mori. In oral toxicity test, the symbiotic bacteria resulted in significant lethal [half lethal concentration of $1.4$\times$10^3$colony-forming units (cfu)/ml] on the ants, while they gave little lethal effect (half lethal concentration of more than $10^{8}$ cfu/ml) on the silkworms. The nematodes, however, gave significant lethal effect [half lethal concentration of 4 infected juveniles (IJs)/ml] on the silkworms, while they did little lethal effect (half lethal concentration of 150,000 IJs/ml) on the ants in topical assays. Both the nematodes and the bacteria did not give lethal effect to the albino rats, Rattus norvegicus, when they were fed orally into the rats. Also, any of these microbial agents were not detected in the internal organs of the treated rats.

• KSBB Journal
• /
• v.17 no.3
• /
• pp.276-282
• /
• 2002

Symbiotic bacteria with highly effective insecticidal activities were isolated and compared with their physiological characteristics from seven species of entomopathogenic nematodes belong to Steinernamatidae and Heterorhabditidae sp., and three of them were identified as Xenorhabdus nematophilus. Culture characteristics, insecticidal activities, pretense activities and fatty acid contents of various symbiotic bactierial isolates were also examined. In the case of cell growth and insecticidal activity, XR-PC and XR-MK were superior to other species when cultured in vitro. The insecticidal activity were highest at the early exponential growth phase, and gradually decreased with time. The protease activity of XR-DR was remarkable compared to other species. In the case of HE-HY, however the pretense activity increased in parallel with cell growth. Interestingly, the fatty acid patterns of Xenorhabdus nematophilus isolated from different emtomopathogenic nematode, showed remarkable differences in their contents of 12:0, 14:0, 16:1 cia 5 and 17:0 cyclo and hydroxy and branch factty acids were varied from 2% to 15% among total fatty acid contents.

• Journal of Sericultural and Entomological Science
• /
• v.51 no.2
• /
• pp.137-141
• /
• 2013

In this study, nucleotide sequence structures of intergenic transcribed spacer (ITS) 1, complete 5.8S ribosomal RNA gene and ITS 2 region were analyzed to identify three Peruvian entomopathogenic fungal isolates. The isolates had highly conserved sequence region in 5.8S rRNA gene and unique sequences in ITS 1 and 2 region among them. 5.8S rRNA gene regions were highly conserved and showed high homoloies among tested isolates. In contrast, ITS region showed species-specific sequence region, resulting in inter-genus differencies. Scanning electron microscopic images of these isolates supported the result of ITS-based identification. From these result, Peruvian entomopathogenic fungal isolate J270, J278, were identified as Beauveria bassiana and J271 was identified as Lecanicillium attenuatum.

• Journal of agriculture & life science
• /
• v.45 no.6
• /
• pp.115-124
• /
• 2011

This study was conducted to find a useful alternative herbivore system with which to study the effects of ultraviolet exposure on the pathogenicity and survival of Korean isolated entomopathogenic nematodes (Heterorhabditis sp. 202 strain, Heterorhabditis sp. Gyeongsan strain, Steinernema sp. 223 strain, S. carpocapsae Pocheon strain, S. glaseri Dongrae strain and S. longicaudum Nonsan strain). Pathogenicity of entomopathogenic nematodes against silkworm, Bombyx mori, differed depending on the nematode species and strain and instar of silkworm challenged. Steinernematidae were relatively more pathogenic to the 5th instar silkworms, whereas Heterorhabditidae were more pathogenic to the 1st instars. UV-C exposure was harmful to entomopathogenic nematodes. All nematodes were killed within 60 minutes of exposure of UV-C, and after 10 min of exposure they caused only 6.7% corrected mortality of silkworms. Silkworms were not infected when they were fed S. carpocapsae Pocheon strain treated mulberry leaves which were exposed to UV intensity of about $2.3mW/cm^2$ for 4 hours in the field. Pathogenicity of S. carpocapsae was not significantly reduced after 1 hour of exposure to $4.0mW/cm^2$ UV intensity on the mulberry leaves against silkworms.

• Proceedings of the Korean Society of Sericultural Science Conference
• /
• 2005.11a
• /
• pp.26-26
• /
• 2005

• Korean Journal of Agricultural and Forest Meteorology
• /
• v.8 no.2
• /
• pp.77-85
• /
• 2006

Entomopathogenic nematodes (EPNs) have been used as biological control agents for control of various agro-forest insect pests, and are especially effective against soil-dwelling insect pests. Effect of soil moisture on pathogenicity of commercial EPNs for white grub control was evaluated in laboratory, pots, and golf courses. Pathogenicity of EPNs in sand column was variable depending on depth, soil moisture, and EPN species or strain. All tested EPNs (Heterorhabditis sp. GSNUH1, Heterorhabditis sp. GSNUH2, Steinernema carpocapsae GSN1, and S. longicaudum Nonsan strain) showed similar pathogenicity against the bait insect, great wax moth (Galleria mellonella) larva at 2 cm deep at a given soil moisture. However, pathogenicity of the Heterorhabditis sp. GSNUH1 strain was decreased with increasing soil moisture. Pathogenicity of S. carpocapsae GSN1 strain was the lowest in 3% soil moisture (v/w) at 7 cm depth. However, there was no difference in pathogenicity between Heterorhabditis sp. GSNUH2 and S. longicaudum Nonsan strain. Although pathogenicity of Heterorhabditis sp. KCTC 0991BP strain showed no difference against the 2nd instar of Exomala orientalis, that of the S. carpocapsae GSN1 strain was decreased in the laboratory depending on soil moisture. Highly pathogenic strain EPN, Heterorhabditis sp. KCTC 0991BP strain, showed higher pathogenicity at 100 mm irrigation than non-irrigation or 10 mm irrigation. However, poor pathogenic strain EPN, S. carpocapsae GSN1 strain, was not different in pathogenicity from the 2nd instar of Exomala orientalis in creeping bentgrass (Agrostis palustris) depending on irrigation amount in the pot. Pathogenicity of EPNs in field experiment at the tee of Ulsan golf club showed a similar trend to that in the pot experiment.