• Mycobiology
• /
• v.46 no.2
• /
• pp.138-146
• /
• 2018

Two-hundred and fifty-five strains of actinomycetes isolated from soil samples were screened for their antagonistic activities against four well-known wood decay fungi (WDF), including a brown rot fungus, Gloeophyllum trabeum and three white rot fungi Donkioporia expansa, Trametes versicolor, and Schizophyllum commune. A dual culture assay using culture media supplemented with heated or unheated culture filtrates of selected bacterial strains was used for the detection of their antimicrobial activity against four WDF. It was shown that Streptomyces atratus, S. tsukiyonensis, and Streptomyces sp. greatly inhibited the mycelial growth of the WDF tested compared with the control. To evaluate the biocontrol efficacy of S. atratus, S. tsukiyonensis, and Streptomyces sp., wood blocks of Pinus densiflora inoculated with three selected Streptomyces isolates were tested for weight loss, compression strength (perpendicular or parallel to the grain), bending strength, and chemical component changes. Of these three isolates used, Streptomyces sp. exhibited higher inhibitory activity against WDF, especially G. trabeum, as observed in mechanical and chemical change analyses. Scanning electron microscopy showed that cell walls of the wood block treated with Streptomyces strains were thicker and collapsed to a lesser extent than those of the non-treated control. Taken together, our findings indicate that Streptomyces sp. exhibits the potential to be used as a biocontrol agent for wood decay brown rot fungus that causes severe damage to coniferous woods.

• The Plant Pathology Journal
• /
• v.29 no.3
• /
• pp.249-259
• /
• 2013

Burkholderia glumae causes rice grain rot and sheath rot by producing toxoflavin, the expression of which is regulated by quorum sensing (QS). The QS systems of B. glumae rely on N-octanoyl homoserine lactone, synthesized by TofI and its cognate receptor TofR, to activate the genes for toxoflavin biosynthesis and an IclR-type transcriptional regulator gene, qsmR. To understand genome-wide transcriptional profiling of QS signaling, we employed RNAseq of the wild-type B. glumae BGR1 with QS-defective mutant, BGS2 (BGR1 tofI::${\Omega}$) and QS-dependent transcriptional regulator mutant, BGS9 (BGR1 qsmR::${\Omega}$). A comparison of gene expression profiling among the wild-type BGR1 and the two mutants before and after QS onset as well as gene ontology (GO) enrichment analysis from differential expressed genes (DEGs) revealed that genes involved in motility were highly enriched in TofI-dependent DEGs, whereas genes for transport and DNA polymerase were highly enriched in QsmR-dependent DEGs. Further, a combination of pathways with these DEGs and phenotype analysis of mutants pointed to a couple of metabolic processes, which are dependent on QS in B. glumae, that were directly or indirectly related with bacterial motility. The consistency of observed bacterial phenotypes with GOs or metabolic pathways in QS-regulated genes implied that integration RNAseq with GO enrichment or pathways would be useful to study bacterial physiology and phenotypes.

• Research in Plant Disease
• /
• v.12 no.3
• /
• pp.153-157
• /
• 2006

In 2005, average temperature was lower, and average rainfall was less than those of previous year. The diseases of rice, barley, pepper, chinese melon, apple and oriental pear were surveyed. Bacterial blight, bacterial grain rot, and panicle disease of rice, black rot of pear, and white rot and bitter rot of apple were severe. Especially, brown rot of rice occurred four times higher than those of previous year. Panicle blight of rice increased about 3 times, compared with the previous year, presumed that the higher rainy days, rainfall and RH promoted spread of the fungal pathogens to panicles of rice. The diseases of rice leaf blast, sudden wilt syndrome, downy mildew and powdery mildew of chinese melon in plastic greenhouse, and virus diseases of hot pepper occurred distinctly less than those of the previous year. Another diseases surveyed occurred similar or less.

• Research in Plant Disease
• /
• v.8 no.1
• /
• pp.1-10
• /
• 2002

Climate in the year of 2001 could be summarized as severe drought from March to May, unusually high temperature in whole plant growth periods and clear weather condition especially in harvesting time of September and October without any typoons. In rice, major diseases such as leaf and panicle blast, bacterial blight, sheath blight and bacterial grain rot developed little due to unfavorable weather conditions, however, brown spot occurred severely due partly to the reduced use of N-fertilizer, Rice stripe virus infection was unusually high mainly in the west coast areas with four times more diseaseD area campared to the previous year, In pepper phytophthora blight was extremely severe in Cheonnam and Cheonbuk provinces, where had frequent rainfalls during growing period. Incidence of major diseases of tomato and cucumber in 2001 was relatively mild. In watermelon, penicillium fruit rot, one of the peculiar disease, spread over major production areas, whereas CGMMV, usually severe in every years was much reduced. Watermelon plants growing in open-fields were more severely diseased than those in plastic houses. Major diseases of chinese melon and strawberry occurred slightly and in particular, sudden wilt syndrome of chinese melon which was severe in 2000 showed mild infections in 2001. Incidence of white rot of garlic and onion was much lower unlike other years due mainly to spring drought and high temperature in the growing period. Infected area of potato bacterial wilt tended to increase in 2001 while fusarium wilt of sweetpotato was decreased. Apple diseases were generally mild, but powdery mildew of pear increased sharply. Barley scab was not severe as seen in other years.

• Research in Plant Disease
• /
• v.19 no.3
• /
• 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.

• Proceedings of the Korean Society of Plant Pathology Conference
• /
• 2003.10a
• /
• pp.136.1-136
• /
• 2003

Bacterial grain rot by Burkholderia gluae cause severe damage in seedling and grain of rice after heading season. This seed-borne pathogen play a role as first infection agent that could be cause disease following cropping season. Until now the direct isolation of the bacteria has some trouble by interference of other bacteria existed inside seed. This study established convenient identification method as simple isolation with KB medium from seed showing symptom and using PCR identification. By this isolation method, B. glumae was isolated from 40 to 50％ in brown rice and inner hull, however, there were saprophytic bacteria and fungi outer hull. In PCR identification with Ogf4 and Ogr3 primer to these 25 isolates, the amplified products were presented in all of the collections but not in 10 saprophytic germs. The isolation rate was constant to 3 months stored seeds. This result provide a rapid and convenient isolation and identification of B. glumae.

• The Plant Pathology Journal
• /
• v.34 no.5
• /
• pp.412-425
• /
• 2018

The Hfq protein is a global small RNA chaperone that interacts with regulatory bacterial small RNAs (sRNA) and plays a role in the post-transcriptional regulation of gene expression. The roles of Hfq in the virulence and pathogenicity of several infectious bacteria have been reported. This study was conducted to elucidate the functions of two hfq genes in Burkholderia glumae, a causal agent of rice grain rot. Therefore, mutant strains of the rice-pathogenic B. glumae BGR1, targeting each of the two hfq genes, as well as the double defective mutant were constructed and tested for several phenotypic characteristics. Bacterial swarming motility, toxoflavin production, virulence in rice, siderophore production, sensitivity to $H_2O_2$, and lipase production assays were conducted to compare the mutant strains with the wild-type B. glumae BGR1 and complementation strains. The hfq1 gene showed more influence on bacterial motility and toxoflavin production than the hfq2 gene. Both genes were involved in the full virulence of B. glumae in rice plants. Other biochemical characteristics such as siderophore production and sensitivity to $H_2O_2$ induced oxidative stress were also found to be regulated by the hfq1 gene. However, lipase activity was shown to be unassociated with both tested genes. To the best of our knowledge, this is the first study to elucidate the functions of two hfq genes in B. glumae. Identification of virulence-related factors in B. glumae will facilitate the development of efficient control measures.

• Research in Plant Disease
• /
• v.9 no.1
• /
• pp.10-17
• /
• 2003

The year of 2002 was very unusual in climatic condition. Warm winter weather, high temperature and drought in March and April, little precipitation in June and early and mid-July and, nearly continuous rain-falls from late July to whole period of August accompanied with low temperature and insufficient sunshine in 2002 resulted in unfavorable conditions for plant growth in one way or another, In relation to the unusual weather, in general, diseases associated with low temperature, poor radiation and much rainfall occurred severely in this year, In rice, incidence of bacterial grain rot, and false smut increased sharply, whereas other major diseases including blast occurred mildly due mainly to the reduced application of nitrogen fertilizer, In vegetables, potato and sweet potato, and fruit trees, incidence of diseases was largely dependent on climatic condition of growth period in particular crops. However, diseases favored low temperature and much rainfall, such as Phytophthora disease increased markedly compared to those of normal years, while anthracnose and soft rot tended to decrease significantly.

• The Plant Pathology Journal
• /
• v.40 no.1
• /
• pp.48-58
• /
• 2024

The oldest and most extensively cultivated form of millet, known as pearl millet (Pennisetum glaucum (L.) R. Br. Syn. Pennisetum americanum (L.) Leeke), is raised over 312.00 lakh hectares in Asian and African countries. India is regarded as the significant hotspot for pearl millet diversity. In the Indian state of Haryana, where pearl millet is grown, a new and catastrophic bacterial disease known as stem rot of pearl millet spurred by the bacterium Klebsiella aerogenes (formerly Enterobacter) was first observed during fall 2018. The disease appears in form of small to long streaks on leaves, lesions on stem, and slimy rot appearance of stem. The associated bacterium showed close resemblance to Klebsiella aerogenes that was confirmed by a molecular evaluation based on 16S rDNA and gyrA gene nucleotide sequences. The isolates were also identified to be Klebsiella aerogenes based on biochemical assays, where Klebsiella isolates differed in D-trehalose and succinate alkalisation tests. During fall 2021-2023, the disease has spread all the pearl millet-growing districts of the state, extending up to 70% disease incidence in the affected fields. The disease is causing considering grain as well as fodder losses. The proposed scale, consisting of six levels (0-5), is developed where scores 0, 1, 2, 3, 4, and 5 have been categorized as highly resistant, resistant, moderately resistant, moderately susceptible, susceptible, and highly susceptible disease reaction, respectively. The disease cycle, survival of pathogen, and possible losses have also been studied to understand other features of the disease.

• Proceedings of the Korean Society of Plant Pathology Conference
• /
• 2003.10a
• /
• pp.66.1-66
• /
• 2003

The aim of this study was to characterize the interactions of rice and Burkholderia glumae, a causal agent of bacterial grain rot of rice, at molecular levels using whole genomic sequences and to identify genes important for pathogenicity and symptom development. To do these, we sequenced whole genome of the bacterium and constructed cosmid clone profiles. We generated pools of mutants using various transposons and determined mutation sites by sequencing rescued plasmids. We focused on studying toxoflavin biosynthetic genes, quorum sensing regulation, and Hrp type III protein secretion systems. We found that two possible operons consisting of five genes are involved in toxoflavin biosynthesis and their expression is regulated by quorum sensing and LysR-type regulator, ToxR. We have isolated the nn PAI of B. glumae and characterized by mutational analyses. The hrp cluster resembled most the putative Type III secretion systems of B. pseudomallei, which is the causative agent of melioidosis, a serious disease of man and animals. The Hrp PAI core region showed high similarity to that of Ralstonia solanacearum and Xanthomonas campestris, however some aspects were dissimilar.