• International Journal of Industrial Entomology and Biomaterials
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• v.6 no.2
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• pp.163-169
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• 2003

Studies were conducted on the effect of pruning time, host age, conidial dispersal and weather parameters on the incidence and severity of mulberry leaf spot (Myrothecium roridum). The disease severity (%) increased with increase in shoot age irrespective of pruning date. Maximum disease severity was observed in plants pruned during first week of April and minimum disease severity in plants pruned during first week of March. Significant (P ＜ 0.01) influence of date of pruning, shoot age and their interaction was observed on severity of the disease. Apparent infection rate (r) was significantly higher during the plant growth period from day 48 to day 55. Average apparent yale was higher in plants pruned during first week of April and least in plants pruned during first week of July. The disease infection was negatively correlated to distance from the inoculum source. Leaf spot severity (%) was influenced by weather parameters. Multiple regression analysis revealed contribution of various combinations of weather parameters on the disease severity. Linear prediction model $(Y ＝ －81.803＋1.176x_2＋0.765x_3) with significant $R^2$ was developed for prediction of the disease under natural epiphytotic condition.

• Mycobiology
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• v.32 no.2
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• pp.79-87
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• 2004

An experiment was carried out to investigate the effects of pre-inoculation with the mycorrhizal fungus Glomus clarum and foliar application of kinetin on the growth of mungbean plant irrigated wht different dilution of seawater. Arbuscular-mycorrhizal(AM) infection significantly increased dry weight, height, chlorophyll, sugar and protein content, nitrogen and phosphorus-use efficiencies, leaf conductivity, transpiration rate, nitrogenase, acid and alkaline phosphates activities of all salinized mungbean plants in comparison with control and non-mycorrhizal plants irrespective of the presence or absence of kinetin. Mycorrrhizal plants showed higher concentrations of N, P, K, Ca and Mg and lower Na/N, Na/P, Na/K, Na/Ca and Na/Mg ratios than non-mycorrhizal plants when irrigated with certain dilution of seawater. Mungbean plants showed 597% and 770% dependency on AM fungus G. clarum in absence and presence of kinetin, respectively, for biomass production under a level of 30% of seawater. The average value of tolerance index for mycorrhizal plants accounted 267% and 364% in absence and presence kinetin respectively. This study provides evidence for the benefits of kinetin which are actually known for mycorrhizal than non-mycorrhzal plants. AM fungus and kinetin protected the host plants against the detrimental effects of salt. However, mycorrhizal infection was much more effective than kinetin applications. Thus management applications of this arbuscular mycorrhizal endophyte(G. clarum) with kinetin could be of importance in using seawater in certain dilution for irrigation in agriculture.

• Proceedings of the Korean Society of Crop Science Conference
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• 2017.06a
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• pp.161-161
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• 2017

Seed endophytes are very remarkable groups of bacteria for their unique abilities of being vertically transmitted and conserved. As plants attain hybrid vigor and heterosis in the process of crossbreeding, this might also lead to the changes in the community structure and diversity of plant endophytes in the hybrid plants ultimately affecting the endophytes of the seeds. It would be interesting to characterize how seed endophyte composition change over time. The objective of this study is to gain insights into the influence of natural crossbreeding and parental lineage in the seed bacterial endophytic communities of two pure inbred lines exploring contributions of the two most important sources of plant endophytes - colonization from external sources and vertical transmission via seeds. Total genomic DNA was isolated from rice seeds and bacterial DNA was selectively amplified by PCR. The diversity of endophytic bacteria was studied through Terminal-Restriction Fragment Length Polymorphism (T-RFLP) analysis. Diversity between the original parents and the pure inbred line may show significant differences in terms of richness, evenness and diversity indices. Heat maps reveal astonishing contributions of both or either parents (IR29 ${\times}$ Pokkali and AT401 ${\times}$ IR31868) in the shaping of the bacterial seed endophytes of the hybrid, FL478 and IC32, respectively. Most of the T-RFs of the subsequent pure inbred line could be traced to any or both of the parents. Comparison of common and genotype-specific T-RFs of parents and their offspring reveals that majority of the T-RFs are shared suggesting higher transmission of bacterial communities common to both parents. The parents influence the bacterial community of their offspring. Unique T-RFs of the offspring also suggest external sources of colonization particularly as the seeds are cultivated in different ecogeographical locations. This study showed that host parental lines contributed greatly in the shaping of bacterial seed endophytes of their offspring. It also revealed transmission and potential conservation of core seed bacterial endophytes that generally become the dominant microbiota in the succeeding generations of plant hosts.

• Proceedings of the Korean Society of Crop Science Conference
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• 2017.06a
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• pp.246-246
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• 2017

Salinity inhibits plant growth and restricts the efficiency of arbuscular mycorrhizal fungi. The selective uptake of nutrients from the soil and their effective transport to host roots make it essential for plant growth and development under salt stress. AMF spore associated bacteria shown to improve mycorrhizal efficiency under stress. Thus, this study aimed to understand the co-inoculation efficiency of AMF and SAB on maize growth and ion homeostasis under salt stress. Two AMF strains and one SAB were inoculated with maize either alone or in combination with one another. The results of our study showed that AMF and SAB co-inoculation significantly improved dry weight and nutrient uptake of maize under salt stress. Co-inoculation significantly reduced proline accumulation in shoots and Na+ accumulation in roots. Co-inoculation treatment also exhibited the high K+/Na+ ratios in roots at 25 mM NaCl. Mycorrhizal colonization showed positive influence for regulation of ZmAKT2, ZmSOS1 and ZmSKOR gene expressions, contributing to K+ and Na+ ion homeostasis. CLSM view showed that SAB were able move and localize into inter and intra cellular spaces of maize roots. In addition, CLSM view of AMF spores showed that gfp-tagged SAB also associated on the spore outer hyaline layer.

• The Plant Pathology Journal
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• v.40 no.1
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• pp.59-72
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• 2024

A comprehensive survey of mungbean-growing areas was conducted to observe leaf spot disease caused by Alternaria alternata. Alternaria leaf spot symptoms were observed on the leaves. Diversity of 50 genotypes of mungbean was assessed against A. alternata and data on pathological traits was subjected to cluster analysis. The results showed that genotypes of mungbean were grouped into four clusters based on resistance parameters under the influence of disease. The principal component biplot demonstrated that all the disease-related parameters (% disease incidence, % disease intensity, lesion area, and % of infection) were strongly correlated with each other. Alt a 1 gene that is precisely found in Alternaria species and is responsible for virulence and pathogenicity. Alt a 1 gene was amplified using gene specific primers. The isolated pathogen produced similar symptoms when inoculated on mungbean and tobacco. The sequence analysis of the internal transcribed spacer (ITS) region, a 600 bp fragment amplified using specific primers, ITS1 and ITS2 showed 100% identity with A. alternata. Potato virus X (PVX) -based silencing vector expressing Alt a 1 gene was constructed to control this pathogen through RNA interference in tobacco. Out of 50 inoculated plants, 9 showed delayed onset of disease. Furthermore, to confirm our findings at molecular level semi-quantitative reverse transcriptase polymerase chain reaction was used. Both phenotypic and molecular investigation indicated that RNAi induced through the VIGS vector was efficacious in resisting the pathogen in the model host, Tobacco (Nicotiana tabacum). To the best of our knowledge, this study has been reported for the first time.

• Geomechanics and Engineering
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• v.21 no.1
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• pp.63-71
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• 2020

Strength anisotropy is a typical feature of thin-bedded rock masses and their strength will be degraded subjected to water immersion effect. Such effect is crucial for the operation of hydropower plant because the impoundment lifts the water level of upstream reservoir and causes the rock mass of nearby slopes saturated. So far, researches regarding mechanical property of natural thin-bedded rock masses and their strength variation under water immersion based on field test method are rarely reported. This paper focuses on a thin-bedded stratified rock mass and carries out field test to investigate the mechanical property and strength variation characteristics. The field test is highlighted by samples which have a large shear dimension of 0.5 m*0.5 m, representing a more realistic in-situ situation than small size specimen. The test results confirm the anisotropic nature of the concerned rock mass, whose shear strength of host rocks is significantly larger than that of bedding planes. Further, the comparison of shear strength parameters of the thin-bedded rock mass under natural and saturated conditions show that for both host rocks and bedding planes, the decreasing extent of cohesion values are larger than friction values. The quantitative results are then adopted to analyze the influence of reservoir impoundment of a hydropower plant on the surrounding rock mass stability of diversion tunnels which are located in the nearby slope bank. It is evaluated that after reservoir impoundment, the strength degradation induced incremental deformations of surrounding rock mass of diversion tunnels are small and the stresses in lining structure are acceptable. It is therefore concluded that the influences of impoundment are small and the stability of diversion tunnels can be still achieved. The finings regarding field test method and its results, as well as the numerical evaluation conclusions are hoped to provide references for rock projects with similar concerns.

• Animal Bioscience
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• v.37 no.2_spc
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• pp.337-345
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• 2024

Ruminants possess a specialized four-compartment forestomach, consisting of the reticulum, rumen, omasum, and abomasum. The rumen, the primary fermentative chamber, harbours a dynamic ecosystem comprising bacteria, protozoa, fungi, archaea, and bacteriophages. These microorganisms engage in diverse ecological interactions within the rumen microbiome, primarily benefiting the host animal by deriving energy from plant material breakdown. These interactions encompass symbiosis, such as mutualism and commensalism, as well as parasitism, predation, and competition. These ecological interactions are dependent on many factors, including the production of diverse molecules, such as those involved in quorum sensing (QS). QS is a density-dependent signalling mechanism involving the release of autoinducer (AIs) compounds, when cell density increases AIs bind to receptors causing the altered expression of certain genes. These AIs are classified as mainly being N-acyl-homoserine lactones (AHL; commonly used by Gram-negative bacteria) or autoinducer-2 based systems (AI-2; used by Gram-positive and Gram-negative bacteria); although other less common AI systems exist. Most of our understanding of QS at a gene-level comes from pure culture in vitro studies using bacterial pathogens, with much being unknown on a commensal bacterial and ecosystem level, especially in the context of the rumen microbiome. A small number of studies have explored QS in the rumen using 'omic' technologies, revealing a prevalence of AI-2 QS systems among rumen bacteria. Nevertheless, the implications of these signalling systems on gene regulation, rumen ecology, and ruminant characteristics are largely uncharted territory. Metatranscriptome data tracking the colonization of perennial ryegrass by rumen microbes suggest that these chemicals may influence transitions in bacterial diversity during colonization. The likelihood of undiscovered chemicals within the rumen microbial arsenal is high, with the identified chemicals representing only the tip of the iceberg. A comprehensive grasp of rumen microbial chemical signalling is crucial for addressing the challenges of food security and climate targets.

• Korean journal of applied entomology
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• v.33 no.1
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• pp.26-32
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• 1994

Electroantennography, wind tunnel observation, and field trapping experiments were carried out to investigate the biological activity of synthetic sex pheromone in the onental tobacco budworm. Heli-couerpa assulta. Two major sex pheromone components of H. assulta, Z9-16' Ald and Z11-16: Ald. elicited a big EAG response in male, but not in female Their mIXture ratios did not give much influence on EAG size Fema]e H assulta showed a great EAG response only to its host plant e extract. EAG size also increased with the amount of mixture from 001 to 10 [lg but rather decreased w when the amount was 1 00 $\mug$. H. assulta always revealed a series of stereotyped behavior in a wind tunnel. The behavioral response was different when the males were stimulated with the sex pheromone containing some minor components, 16: AId and Z9.16: Ac, or being different in mixing ratios of the two major components. The best ratio of the sex phemmone components for a attracting H assulta male adults was 20-25: 1 between Z9-16: Aid and Z11-16: Ald in net house a and red pepper field experiments in Korea When the lure contamed Z9-16: OH, attracting power rapidly decreased. The synthetic sex pheromone showed a strong attraction when compared to virgin females

• Korean Journal of Soil Science and Fertilizer
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• v.37 no.4
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• pp.235-244
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• 2004

In this study, we compared the levels of methylotrophic bacterial community diversity in the leaf samples of 19 rice cultivars collected from three regions of Korea. Nineteen pink pigmented isolates showing characteristic growth on methanol were obtained. Physiological and biochemical characters of each isolate were examined according to methods described in Bergey's Manual of Systematic Bacteriology. When phylotypes were defined by performing numerical analysis of 37 characteristics, four distinct clusters were formed. The two reference strains, Methylobacterium extorquens AM1 and Methylobacterium fujisawaense KACC10744 were found to group under cluster IV and cluster III respectively. Cluster I diverged on the basis of nitrate reduction and four isolates showed tolerance upto 0.5 M NaCl concentrations. Two strains in cluster I and III were found to possess methane utilizing properties. Most of the isolates in all the four clusters utilized monosaccharides, disaccharide and polyols as carbon source. When the isolates were subjected for indole-3-acetic acid (IAA) analysis in the presence of L-tryptophan, only 8 isolates exhibited IAA production. In addition, the nitrogen source in the medium was found to influence the IAA production. Addition of $(NH_4)_2SO_4$ in the medium led to a 2 to 30 fold increase in the indole synthesis. However, $KNO_3$, $NH_4NO_3$ and $NH_4Cl$ substitution did not significantly stimulate the synthesis of IAA in the growth medium. Result of gnotobiotic root elongation assay significantly increased roots and shoots lengths, and number of lateral roots, which is mediated by IAA production in the culture medium. The rice seedlings primary roots from seeds treated with methylotrophic isolates were on average 27 to 56% longer than the roots from seeds treated with the uninoculated seeds. In addition, application of different high concentrations of authentic IAA ($400g\;mL^{-1}$) to roots of rice seedlings inhibited root growth. However, the IAA concentration from 10 to $200g\;mL^{-1}$, IAA promoted root growth of rice seedlings. These results suggest that bacterial IAA plays a major role in the development of the host plant root system.