• 한국농림기상학회지
• /
• 제8권2호
• /
• 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.

• 한국식품과학회지
• /
• 제33권4호
• /
• pp.486-491
• /
• 2001

국내외에서 분양 받고 국내식육에서 분리된 총 100균주의 Y. enterocolitica에 대한 병원성여부를 HEp-2세포 침투성 시험법을 기준으로 하고 여러 가지 병원성 확인 방법을 비교하였다. 혈청형만으로 병원성을 판단하기에는 충분하지 않았고 이외의 방법 즉, esculin과 salicin시험, pyrazinamidase 시험, biotype 등의 생화학적 특성에 바탕을 둔 실험 단독으로 병원성을 판단하기에는 완전하지 않았다. D-xylose 발효실험, CRMOX agar 시험과 자동응고반응(Autoagglutination)들은 병원성확인에 보조적인 역할만을 할 수 있었다. HEp-2 세포 침투성 시험법은 시간과 노력이 많이 소요되므로 이 방법을 대치할 수 있는 간단하고 신속, 정확하게 Y. enterocolitica 병원성을 확인할 수 있는 방법은 esculin시험에서 음성반응을 보이는 것만 PCR시험을 행하여 판별하는 것이라고 사려된다.

• The Plant Pathology Journal
• /
• 제17권4호
• /
• pp.210-215
• /
• 2001

The phenotype of Rhizoctonia solani KR-13 was randomly segregated to both melanin-producing (M+) and non-producing (M-) types through successive cultures on PDA. M+type with dark melanin showed strong pathogenicity to rice and self-anastomosis. Meanwhile, M- type with white or less-melanized mycelia showed very weak pathogenicity and non-self-anastomosis. Melanin production of R. solani was affected by incubation temperature in both M+ and M- types, but not by light treatment. The application of tricyclazole, an inhibitor of fungal melanin biosynthesis, showed no controlling effect on R. solani causing rice sheath blight. Results of this study showed that melanization of mycelia of R. solani is an important pathogenicity factor in rice.

• 식물병연구
• /
• 제15권1호
• /
• pp.46-50
• /
• 2009

Cytochalasin E (CE) is a secondary metabolite secreted by Rosellinia necatrix, caused by white root rot, and has toxicity to apple as a toxin during disease progress. This study was conducted to demonstrate the relationship between the production of CE and its pathogenicity. CE producing isolates and non-producing isolates of R. nectatrix were isolated from the mycerial mat of diseased roots and was detected on that using a TLC and HPLC analysis and in vivo pathogenicity test. CE non-producing isolates were not pathogenic to apple roots and not detected CE by TLC and HPLC analysis. It was shown that the production of CE was related to the pathogenicity of R. nectatrix.

• 한국응용곤충학회지
• /
• 제36권2호
• /
• pp.179-184
• /
• 1997

농약이 한국산 곤충병원성곰팡이 Beauveria bassiana와 Metarhizium anisopliae에 미치는 영향을 알아본 결과, SMAY배지상에서의 농약농도에 따른 곰팡이 포자형성수는 metalaxyl과 tolclofos-methyl 처리에서는 대조구와 큰 차이가 없었으나. fenitrothion과 mepronil 처리에서는 권장량의 $\frac{1}{2}$배 처리에서도 포자형성이 미약하였다. 농약과의 동시 처리가 곤충병원성 곰팡이에 미치는 영향을 알아보기 위하여 농약희석액에 병원성 곰팡이를 1-5시간 동안 침지시켜 병원성을 알아본 결과 전 약종에서 100%의 병원성을 나타내었다. 배추밭에서 농약전처리가 M. anisopliae의 병원성에 끼치는 영향을 알아본 결과는 Bt나 teflubenzuron, metalaxyl, carbofuran 처리구는 대조구와 병원성에서 차이를 보이지 않았으나 alachlol 처리구에서는 병원성이 80% 이하로 떨어졌다. 잔디밭에서 농약의 후처리가 병원성곰팡이의 병원성과 지속성에 미치는 영향을 알아본 바 iprodione+thiram과 tolclofos-methyl 처리구에서는 4달째까지 병원성이 지속되었고 fenitrothion처리구에서는 3개월 후부터 B. bassiana와 M. anisopliae의 병원성이 상실되었으며 mepronil처리구에서는 M. anisopliae가 병원성을 상실하였다.

• The Plant Pathology Journal
• /
• 제37권6호
• /
• pp.555-565
• /
• 2021

Bacteriophages infecting Acidovorax citrulli, the causal agent of bacterial fruit blotch, have been proven to be effective for the prevention and control of this disease. However, the occurrence of bacteriophage-resistant bacteria is one of hurdles in phage biocontrol and the understanding of phage resistance in this bacterium is an essential step. In this study, we aim to investigate possible phage resistance of A. citrulli and relationship between phage resistance and pathogenicity, and to isolate and characterize the genes involved in these phenomena. A phage-resistant and less-virulent mutant named as AC-17-G1 was isolated among 3,264 A. citrulli Tn5 mutants through serial spot assays and plaque assays followed by pathogenicity test using seed coating method. The mutant has the integrated Tn5 in the middle of a cupin protein gene. This mutant recovered its pathogenicity and phage sensitivity by complementation with corresponding wild-type gene. Site-directed mutation of this gene from wild-type by CRISPR/Cas9 system resulted in the loss of pathogenicity and acquisition of phage resistance. The growth of AC-17-G1 in King's B medium was much less than the wild-type, but the growth turned into normal in the medium supplemented with D-mannose 6-phosphate or D-fructose 6-phosphate indicating the cupin protein functions as a phosphomannos isomerase. Sodium dodecyl sulfa analysis of lipopolysaccharide (LPS) extracted from the mutant was smaller than that from wild-type. All these data suggest that the cupin protein is a phosphomannos isomerase involved in LPS synthesis, and LPS is an important determinant of pathogenicity and phage susceptibility of A. citrulli.

• The Plant Pathology Journal
• /
• 제23권2호
• /
• pp.62-69
• /
• 2007

Twenty-nine isolates of Fusarium solani, originally isolated from diseased cotton roots in Egypt, were evaluated for their ability to cause symptoms on four genetically diverse cotton cultivars. Analysis of variance showed highly significant variance among cultivars, and isolates as well as the isolate x genotype interactions were highly significant(p < 0.0001). Although most isolates showed intermediate pathogenicity, there were two groups of isolates that showed significant differences in pathogenicity on all four cultivars. None of the cultivars were found to be immune to any of the isolates. On all cultivars, there were strong significant positive correlations between dry weight and each of preemergence damping-off, survival, and plant height. Considering 75% similarity in virulence, two groups comprising a total of 29 isolates were recognized. Ninety-three percent of the isolates have the same pathogenicity patterns with consistently low pathogenicity, and narrow diversity of virulence. Isolates Fs4 and Fs5 shared the same distinct overall virulence spectrum with consistently high pathogenicity. There was no clear-cut relationship between virulence of the isolates based on reaction pattern on 4 cultivars and each of host genotype, previous crop, and geographic origin.

• Mycobiology
• /
• 제44권1호
• /
• pp.38-47
• /
• 2016

The ascomycete fungus Mycosphaerella graminicola (synonym Zymoseptoria tritici) is an important pathogen of wheat causing economically significant losses. The primary nutritional mode of this fungus is thought to be hemibiotrophic. This pathogenic lifestyle is associated with an early biotrophic stage of nutrient uptake followed by a necrotrophic stage aided possibly by production of a toxin or reactive oxygen species (ROS). In many other fungi, the genes CREA and AREA are important during the biotrophic stage of infection, while the NOXa gene product is important during necrotrophic growth. To test the hypothesis that these genes are important for pathogenicity of M. graminicola, we employed an over-expression strategy for the selected target genes CREA, AREA, and NOXa, which might function as regulators of nutrient acquisition or ROS generation. Increased expressions of CREA, AREA, and NOXa in M. graminicola were confirmed via quantitative real-time PCR and strains were subsequently assayed for pathogenicity. Among them, the NOXa over-expression strain, NO2, resulted in significantly increased virulence. Moreover, instead of the usual filamentous growth, we observed a predominance of yeast-like growth of NO2 which was correlated with ROS production. Our data indicate that ROS generation via NOXa is important to pathogenicity as well as development in M. graminicola.

• The Plant Pathology Journal
• /
• 제35권2호
• /
• pp.91-99
• /
• 2019

Mitogen-activated protein kinase (MAPK) cascades in fungi are ubiquitously conserved signaling pathways that regulate stress responses, vegetative growth, pathogenicity, and many other developmental processes. Previously, we reported that the AbSte7 gene, which encodes a mitogen-activated protein kinase kinase (MAPKK) in Alternaria brassicicola, plays a central role in pathogenicity against host cabbage plants. In this research, we further characterized the role of AbSte7 in the pathogenicity of this fungus using ${\Delta}AbSte7$ mutants. Disruption of the AbSte7 gene of A. brassicicola reduced accumulation of metabolites toxic to the host plant in liquid culture media. The ${\Delta}AbSte7$ mutants could not efficiently detoxify cruciferous phytoalexin brassinin, possibly due to reduced expression of the brassinin hydrolase gene involved in detoxifying brassinin. Disruption of the AbSte7 gene also severely impaired fungal detoxification of reactive oxygen species. AbSte7 gene disruption reduced the enzymatic activity of cell walldegrading enzymes, including cellulase, ${\beta}$-glucosidase, pectin methylesterase, polymethyl-galacturonase, and polygalacturonic acid transeliminase, during host plant infection. Altogether, the data strongly suggest the MAPKK gene AbSte7 plays a pivotal role in A. brassicicola during host infection by regulating multiple steps, and thus increasing pathogenicity and inhibiting host defenses.

• 한국연초학회지
• /
• 제12권1호
• /
• pp.9-18
• /
• 1990

To study the determinants which are involved in the loss of pathogenicity in wilt-inducing Pseudomoms solamcewum, several physlologica I functions were compared in a virulent P. solanacearum strain and an avirulent, spontaneously derived mutant strain. The polyacrylamide gel electrophoresis showed the distinction between two strains in the patterns and the relative intensity of proteins produced intracellularly or extracellularly. Enzyme assays showed that the level of polygalacturonase activity in the culture filtrate of the avirulent mutant was markedly reduced, while carboxymethylcellulase(rondoglucanase) activity in both strains were nearly negligible. These results suggest that the loss of pathogenicity in mutant strain is attributed in part to the reduced production of polygalacturonase. In audit ion, comparative analyses by agarose gel electrophoresis of DNA molecules isolated from both strains show that the pathogenicity genes of p. solanaceerum are not located on plasmid but are on chromosome.