Jang Hyun Hur

Characterization of Streptomycetes Causing Potato Common Scab in Korea

Six representative Korean strains of streptomycetes (S33, S27, S71, S63, S77, and S78) that were pathogenic to potato were characterized based on phenotypic properties, analysis of 16S rRNA genes, production of thaxtomin A, and presence of nec1 and ORFtnp gene homologs. Strains S33 and S27 had typical characteristics of Streptomyces scabies and S. turgidiscabies, respectively, producing thaxtomin A and hybridizing to genes of nec1 and ORFtnp. Strain S71 produced thaxtomin A and had phenotypic and phylogenetic properties similar to those of S. acidiscabies, except having a greater minimum growth pH (4.5), production of a melanoid pigment on tyrosine agar, and failure to hybridize with nec1 and ORFtnp gene probes. In contrast, strains S63, S77, and S78 were phenotypically different from described scab pathogens. Spore colors of strains S63 and S77 were yellow-white or pale orange, respectively, with rectiflexuous chains. Strain S78 had thin and compact spores unlike typical S. acidiscabies (ATCC 49003). Phylogenetic analysis of strains S63, S77, and S78 based on 16S rRNA gene sequences showed low homology to that of described scab pathogens (less than 97.3, 96.0, and 96.3%, respectively). Strain S78 produced thaxtomin A, but did not have homologous sequences to nec1 and ORFtnp genes. Production of thaxtomin A and gene homologs of nec1 and ORFtnp were not detected in strains S63 and S77. All three strains grow at low pH, with minimal growth at pH 3.5 (S77 and S78) or 4.5 (S63). Streptomyces strains S63, S77, and S78 are novel pathogenic streptomycetes adapted to acidic soil conditions in Korea.

Complete Genome Sequence of Japanese Erwinia Strain Ejp617, a Bacterial Shoot Blight Pathogen of Pear

The Japanese Erwinia strain Ejp617 is a plant pathogen that causes bacterial shoot blight of pear in Japan. Here, we report the complete genome sequence of strain Ejp617 isolated from Nashi pears in Japan to provide further valuable insight among related Erwinia species.

Residual Characteristics of Bistrifluron and Chlorantraniliprole in Strawberry (Fragaria ananassa Duch.) for Establishing Pre-Harvest Residue Limit

BACKGROUND: Pesticide residue analysis is essentially required for safety evaluation of agricultural products. Bistrifluron and chlorantraniliprole have been currently considered as potentials to deeply evaluate their residues in agricultural products because they are frequently found in strawberry. This work was performed to investigate the residual patterns of bistrifluron and chlorantraniliprole in strawberry after harvest. METHODSANDRESULTS:Strawberry was treatedwith bistrifluron andchlorantraniliprole 0, 1, 2, 3, 5, 7 and10days before harvest under greenhouse conditions. The strawberry samples were subjected to solvent and solid phase extractions followed by LC-MS/MS analysis. There covery percentages of bistrifluron and chlorantraniliprole for tified in the control samples ranged from approximately 82 to 103% with the method limit of 0.005 mg/kg. The concentrations of bistrifluron and chlorantraniliprole in strawberry samples decreased significantly in 10 days after treatment, giving the safety levels of 0.04 to0.06mg/kg at 10 days after application, as consideredmaximumresidue limit. The half-lives of bistrifluron and chlorantraniliprole based on first order kinetics were determined to 6.3 days and 6.4 days, respectively. CONCLUSION:Bistrifluron and chlorantraniliprole are suggested to use in strawberry 10 days before harvest to reach residual safety levels.

Establishment of Pre-Harvest Residue Limits (PHRLs) of Fluopicolide and Metrafenone in Cherry Tomato ( Lycopersicon esculentum Mill.)

BACKGROUND: The present investigation was aimed to predict the pre-harvest residue limits (PHRLs) of the fluopicolide and metrafenone on cherry tomato and to estimate their half-life and characteristics of the residues.METHODS AND RESULTS: Pesticides were treated once on cherry tomato in field 1 and 2 under the standard application rate. The samples were collected 7 times at the end of 0(2 hours after pesticides spaying), 1, 2, 3, 5, 7 and 10 days before harvest. Residues of fluopicolide and metrafenone were analyzed by the LC-MS/MS. In this study, the method limit of quantification (MLOQ) for both fluopicolide and metrafenone in cherry tomato was found to be 0.005 mg kg-1. Their recovery levels were 92.7∼94.8% and 82.6∼88.0%, shown with coefficient of variation of less than 10%. Half-life of fluopicolide and metrafenone in field 1 and 2 were found to be 15.0 days and 12.8 days, 18.9 days and 21.5 days, respectively.CONCLUSION: Based on the results, this study shows the level of PHRL on cherry tomato is 0.27 mg/kg for fluopicolide and 2.29 mg/kg for metrafenone at 10 days before harvesting. The present study indicates the residues of both pesticides on cherry tomato will be below maximum residue limit (MRL) at harvest.

Species-specific Detection of Erwinia pyrifoliae by PCR Assay Using Enterobacterial Repetivive Intergenic Consensus (ERIC) Primers

We designed a sensitive and specific PCR-based method with enterobacterial repetitive intergenic consensus (ERIC) primer to detect Erwinia pyrifoliae, which cause shoot blight in Asian pear, from a mixed culture and infected plant materials. The primers specifically detected only E. pyrifoliae and showed no cross-reactivity with other bacterial phytopathogens.

Identification of a Genetic Locus Related to Antivirus Production in Pseudomonas fluorescence strain Gpf01 Against Cucumber mosaic virus

Pseudomonas fluorescens strain Gpf01, isolated from ginseng rhizosphere showed antiviral activity against Cucumber mosaic virus, when tested in a local host of CMV, Chenopodium amaranticolor. Transposon mutant library of Gpf01 was prepared using pGS9::Tn5 and the mutant Gpf01-RS19 was found to loose antiviral production. We developed primers from the flanking region of Tn5 and found a cosmid clone pAV1123, harboring 1.2 kb antiviral compound producing (avcf01) locus. When a sub-clone pPH9, which carried 9.3 kb region of pAV1123, was introduced into antivirus deficient P. fluorescens wild type strain B16, it exhibited antiviral activity. Using Tn3-gus mutagenesis and complementation analysis, it was found that the genes related to antiviral activity production resided in a 9.3 kb HindIII-HindIII fragment of pAV1123, indicating that the plasmid carries an essential genes promoting antiviral activity.

An insert in the Hpy region of hscp in Heliothis virescens (Lepidoptera: Noctuidae) reveals a possible CORE-SINE of insects

Abstract  A new putative transposon was identified in the tobacco budworm, Heliothis virescens. This transposon was characterized as a full length CORE‐SINE (65 bp of “CORE” core specific nucleotide short interspersed elements) that resembled sequences from three other lepidopterans and humans. In particular, the A‐box and B‐box regions of this sequence most closely conformed to the signature of CORE‐SINEs from widely divergent species. This CORE‐SINE was present as a polymorphism in a hypervariable region of the gene hscp, which is the target of pyrethroid insecticides and other xenobiotics in the nerve axon. We described this new putative transposon as Noct‐1 due to its presence in a noctuid moth. This is the first description of a full‐length CORE‐SINE with the A‐box, B‐box, target site duplication, and candidate core domain from an insect.

Study on Residual Properties of Dimethomorph and Pyraclostrobin in the Amaranthus (Amaranthus mangostanus L.)

본 연구는 소면적 재배작물 비름(Amaranthus mangostanus L.) 중 살균제 dimethomorph와 pyraclostrobin의 잔류량을 분석하여 안전사용기준을 설정하고 비름의 잔류허용기준 설정에 자료로 활용하기 위하여 수행하였다. Dimethomorph와 pyraclostrobin 농약은 유사작물의 안전사용기준에 준하여 7일 간격으로 2회, 3회 3반복으로 살포하였으며, 시료를 수확한 후 분석하였다. Dimethomorph 및 pyraclostrobin은 LC-MS/MS를 이용하여 분석하였으며, 분석검출한계는 모두 0.01 mg L−1, 회수율은 dimethomorph 89.6~96.3%, pyraclostrobin (BF500-3) 70.8~103.2%이었다. 비름 중 농약에 대한 잔류량은 dimethomorph의 경우 4.56~0.11 mg L−1이었으며, pyraclostrobin의 경우 3.97~0.20 mg L−1이었다. 두 약제의 잔류량은 수확 전 처리일이 수확일에 가깝거나 처리횟수가 많아지면서 높아지는 뚜렷한 경향을 보였으며, 유사작물인 엇갈이배추의 잔류허용기준을 준용하여(dimethomorph 5.0 mg L−1, pyraclostrobin 0.5 mg L−1) MRL을 추천하고자 하였다. 다만 본 논문 작성 시점인 2018년 4월 현재 두 약제의 MRL이 각각 5.0 mg L−1으로 대한민국 식품공전에 고시되어있으며, 소면적 재배작물인 비름의 안전사용기준은 수확 14일 전 까지 3회 이내 처리로 등록되어 있음을 확인할 수 있다. 본 연구의 잔류량으로부터 산출한 이론적일일최대섭취량(TMDI), 즉 ADI 대비 식이섭취율(% ADI)는 dimethomorph와 pyraclostrobin에 대하여 각각 17.07%, 28.11%이었다. 본 연구 결과를 바탕으로 비름 중 dimethomorph 및 pyraclostrobin의 안전사용기준과 잔류허용기준이 설정된다면 비름 재배농가의 적절한 농약사용과 소비자들에게 안전한 농산물을 공급하는데 기여할 것으로 사료된다.