• 한국식물병리학회:학술대회논문집
• /
• 한국식물병리학회 2004년도 The 2004 KSPP Annual Meeting & International Symposium
• /
• pp.36-38
• /
• 2004

Ethaboxam is a new fungicidal active ingredient that inhibits growth of plant pathogens specifically belonging to Oomycetes with protective, curative, systemic and translaminar activity in plants. Modes of action studies revealed that ethaboxam simultaneously inhibits cytoskeleton formation and mitochondrial respiration of Phytophthora infestans at low concentrations. There have been no indications of resistance development when tested for baseline resistance monitoring to 261 isolates of P. infestans in Korea and Europe and 150 populations of Plasmopara viticola populations in Europe for 3 years since 2000. In a selective study with vine trees artificially inoculated with P. viticola repeatedly for 10 generations in greenhouse, there have been no changes in sensitivity to ethaboxam among four natural populations of P. viticola. Furthermore, ethamoxam has not shown any cross resistance with azoxystrobin, mefenoxam, dimethomorph and cymoxanil. Based on the study results from modes of action and resistance development, ethaboxam appears to be unlikely to develop resistance in field applications.

• The Plant Pathology Journal
• /
• 제26권4호
• /
• pp.421-423
• /
• 2010

New sources of barley (Hordeum vulgare L.) resistant to spot blotch, caused by Cochliobolus sativus, are needed to provide effective resistance because of the rapid change pathotype patterns of C. sativus in fields. The purposes of our study were to develop a method to screen barley for resistance to spot blotch disease and then use this methodology to screen barley genotypes for resistance to the major virulent pathotype Pt4 in barley populations in Syria. A transparent tape method, in which a conidial suspension of C. sativus was dropped onto transparent tape and placed, treated-side down, on the second leaf surface of barley plants. Disease symptoms of fungus were easily detected on the leaves covered by the transparent tape after 48h of inoculation. The transparent tape method was repeatable and the disease scores obtained were correlated (r = 0.91, P = 0.001) with those obtained by the seedling assay. This method may be beneficial in various plant pathology breeding programs.

• 한국응용곤충학회지
• /
• 제31권3호
• /
• pp.256-275
• /
• 1992

Insects are among the most important abiotic and biotic constraints to rice production. National rice research programs are in various stages in the development and implementation of integrated pest management (IPM) stratagies for rice insect control. Among the various control tactics, insect resistant cultivars are sought as the major tactic in rice IPM. Through the activities of interdisciplinary teams of scientists significant progress has been made in the development and release of insect resistant cultivars to farmers. Because of its compatibility with other control tactics insect resistance has proven to fit well into the IPM approach to rice insect control agents and minimize the need for insecticide applications. The development of biotypes which overcome the resistance in rice plants has been a significant constraint in the breeding of rice for resistance to insects. Most notable examples in Asia are the green leafhopper, Nephotettix virescens, brown planthopper, Nilaparvata lygens and the Asian rice gall midge, Orseolia oryzae. The current breeding stratege is to develop rice cultivars with durable resistance on which virulent biotypes cannot adapt. In spite of the significant progress made in the breeding of insect resistant cultivars there are still numerous important rice insect species for which host plant resistance as a control tactic has not been fully utilized. Advances in biotechnology provide promise of solving some of the problems that have limited the use of host plant resistance as a major tactic in the integrated management of rice insect pests.

• The Plant Pathology Journal
• /
• 제36권2호
• /
• pp.111-120
• /
• 2020

Powdery mildew of Indian mustard (Brassica juncea), caused by Erysiphe cruciferarum, is emerging as major problem in India. All the Indian mustard cultivars presently grown in India are highly susceptible to powdery mildew and so far no resistance source has been reported. In this study, with an aim to identify resistant source, 1,020 Indian mustard accessions were evaluated against E. cruciferarum PMN isolate, at Wellington, The Nilgiris, Tamil Nadu, India under natural hot spot conditions. The study identified one accession (RDV 29) with complete resistance against E. cruciferarum PMN isolate for the first time, which was consistent in five independent evaluations. Genetic analysis of F₁, F₂ and backcross populations obtained from the cross RSEJ 775 (highly susceptible) × RDV 29 (highly resistant) for two season revealed that the resistance is governed by two genes with semi-dominant and gene dosage effect. Further, a new disease rating system using six scales (0, 1, 2, 3, 4, and 5) has also been proposed in this study to score powdery mildew based on progress of fungal growth in different plant parts of the F₂ population. The outcome of this study viz. newly identified powdery mildew-resistant Indian mustard accession (RDV 29), information on inheritance of resistance and the newly developed disease rating scale will provide the base for development of powdery mildew-resistant cultivars of Indian mustard.

• The Plant Pathology Journal
• /
• 제33권4호
• /
• pp.402-409
• /
• 2017

Cyclic dipeptides (CDPs) are one of the simplest compounds produced by living organisms. Plant-growth promoting rhizobacteria (PGPRs) also produce CDPs that can induce disease resistance. Bacillus vallismortis strain BS07 producing various CDPs has been evaluated as a potential biocontrol agent against multiple plant pathogens in chili pepper. However, plant signal pathway triggered by CDPs has not been fully elucidated yet. Here we introduce four CDPs, cyclo(Gly-L-Pro) previously identified from Aspergillus sp., and cyclo(L-Ala-L-Ile), cyclo(L-Ala-L-Leu), and cyclo(L-Leu-L-Pro) identified from B. vallismortis BS07, which induce disease resistance in Arabidopsis against Pseudomonas syringae infection. The CDPs do not directly inhibit fungal and oomycete growth in vitro. These CDPs require PHYTOALEXIN DEFICIENT4, SALICYLIC ACID INDUCTION DEFICIENT2, and NONEXPRESSOR OF PATHOGENESIS-RELATED PROTEINS1 important for salicylic acid-dependent defense to induce resistance. On the other hand, regulators involved in jasmonate-dependent event, such as ETHYLENE RECEPTOR1, JASMONATE RESPONSE1, and JASMONATE INSENSITIVE1, are necessary to the CDP-induced resistance. Furthermore, treatment of these CDPs primes Arabidopsis plants to rapidly express PATHOGENESIS-RELATED PROTEIN4 at early infection phase. Taken together, we propose that these CDPs from PGPR strains accelerate activation of jasmonate-related signaling pathway during infection.

• 한국동물위생학회지
• /
• 제46권1호
• /
• pp.35-45
• /
• 2023

Pathogenic Escherichia coli is the cause of a wide range of diseases in pigs, including diarrhea, edema disease, and septicemia. Diarrhea caused E. coli may result in significant economic losses, making pathogenic E. coli an important pathogen for the swine industry. This study investigated the prevalence of virulence factor genes, antimicrobial resistance phenotypes, and resistance genes in E. coli isolated from feces of piglets in Korea between 2017 and 2020. As a result, 119 pathogenic E. coli isolates were obtained from 601 fecal samples. The F4 adhesin gene and the STb enterotoxin gene were commonly present in E. coli isolated from diarrhea samples. The dominant virulotypes of isolates from diarrhea samples were STb, Stx2e, and F4:LT:STb. More than 80% of the screened isolates were resistant to ampicillin, sulfisoxazole, chloramphenicol, or tetracycline. To confirm the resistance mechanisms for β-lactam or quinolone, we investigated the genotypic factors of resistance. Each of the ceftiofur-resistant E. coli produced an extended-spectrum β-lactamase encoded by bla_CTX-M-14, bla_CTX-M-27, and bla_CTX-M-55. And all ciprofloxacin-resistant E. coli harbored mutations in quinoloneresistance-determining-regions. In addition, some of the ciprofloxacin-resistant E. coli contained the plasmid-mediated-quinolone-resistance genes such as qepA, qnrB1, or qnrD. This study has confirmed that the F4 fimbria and the STb enterotoxin are the most predominant in pathogenic E. coli isolated from piglets with diarrhea in Korea and there is a great need for responsible and prudent use of antimicrobials to treat colibacillosis.

• 한국식물병리학회지
• /
• 제14권6호
• /
• pp.682-688
• /
• 1998

Fungicide resistance of 48 isolates of Botrytis cinerea collected from citrus in Cheju was investigated and genetic diversity was analyzed with random amplified polymorphic DNA(RAPD). High levels of resistance to benzimidazole fungicides benomyl and thiophanate-methyl and N-phenylcarbamate fungicide diethofencarb were observed. Negative cross resistance was clear between benzimidazole and N-phenylcarbamate fungicides, and multiple resistance to the fungicides was also observed. There was cross resistance among the dicarboximide fungicides procymidione, vinclozolin and iprodione as it was observed between the benzimidazole fungicides benomyl and thiophanate-methyl. The lowest levels of resistance were to the dicarboximide fungicides, but no sensitive isolate to polyoxin B was observed. The isolates showed genetically diverse RAPD profiles according to the geographic origin collected, but there was no significant correaltion between RAPD profiles of genomic DNA and the levels of fungicide resistance of the isolates. The isolates showed genetically diverse RAPD profiles, indicating that genetic differentiation had already occurred in the populations of B. cinerea distributed in Cheju.

• 한국균학회지
• /
• 제52권2호
• /
• pp.73-96
• /
• 2024

Root and stem rot caused by Phytophthora palmivora is one of the most serious diseases affecting durian production in Thailand where metalaxyl, an effective fungicide against oomycetes, has been used extensively for a long period to control this disease. Although field isolates of P. palmivora resistant to metalaxyl exist in Thailand, a molecular basis for P. palmivora has not yet been elucidated regarding metalaxyl resistance. The current study tested whether P. palmivora RPA1 (the DNA-directed RNA polymerase I subunit gene), a homolog gene of RPA190 associated with metalaxyl resistance in some isolates of Phytophthora infestans, had a role in the resistance mechanism toward metalaxyl. In total, 40 durian-derived isolates of P. palmivora were assessed for metalaxyl sensitivity using a mycelial growth inhibition assay. The effective concentrations for 50% mycelial growth inhibition values for all isolates tested were in the range 0.01-872.88 mg/L. The isolates were clustered into three groups: sensitive (n=23), moderately resistant (n=11), and resistant (n=6) groups. No polymorphism was revealed based on multiple alignment analysis of the amino acid sequences translated from the corresponding DNA sequences in the region of RPA1 of the metalaxyl-sensitive (n=5), moderately resistant (n=2), and resistant isolates (n=6). Furthermore, investigation of the RPA1 expression among these representative isolates (n=3, each group) indicated that RPA1 expression may not be involved in the regulation of P. palmivora resistance to metalaxyl. Based on this line of evidence, there was no detected relationship regarding metalaxyl resistance and P. palmivora RPA1.

• The Plant Pathology Journal
• /
• 제39권6호
• /
• pp.584-591
• /
• 2023

Active plant immune response involving programmed cell death called the hypersensitive response (HR) is elicited by microbial effectors delivered through the type III secretion system (T3SS). The marine bacterium Hahella chejuensis contains two T3SSs that are similar to those of animal pathogens, but it was able to elicit HR-like cell death in the land plant Nicotiana benthamiana. The cell death was comparable with the transcriptional patterns of H. chejuensis T3SS-1 genes, was mediated by SGT1, a general regulator of plant resistance, and was suppressed by AvrPto1, a type III-secreted effector of a plant pathogen that inhibits HR. Thus, type III-secreted effectors of a marine bacterium are capable of inducing the nonhost HR in a land plant it has never encountered before. This suggests that plants may have evolved to cope with a potential threat posed by alien pathogen effectors. Our work documents an exceptional case of nonhost HR and provides an expanded perspective for studying plant nonhost resistance.

• 식물병연구
• /
• 제19권3호
• /
• pp.177-182
• /
• 2013

Resvestrol has been known to inhibit bacterial and fungal growth in vitro, and can be accumulated in plant to concentrations necessary to inhibit microbial pathogens. Hence, stilbene synthase gene has been used to transform to synthesize resveratrol in heterologous plant species to enhance resistance against pathogens. In the present study, we investigated the antimicrobial activities of resveratrol and piceid to bacterial and fungal pathogens, which causing severe damages to rice plants. In addition, disease resistance was compared between transgenic rice varieties, Iksan 515 and Iksan 526 transformed with stlibene synthase gene and non-transgenic rice varieties, Dongjin and Nampyeong. Minimum inhibitory concentration of resveratrol for Burkolderia glumae was 437.5 ${\mu}M$, and the mycelial growth of Biplaris oryzae was slightly inhibited at concentration of 10 ${\mu}M$. However, other bacterial and fungal pathogens are not inhibited by resveratrol and piceid. The expression of the stilbene synthase gene in Iksan 515 and Iksan 526 did not significantly enhanced resistance against bacterial grain rot, bacterial leaf blight, sheath blight, and leaf blight. This study is the first report on the effect of resveratrol and piceid against pathogens of rice plant, and changes of disease resistance of transgenic rice plants transformed with stilbene synthase gene.