• Korean Journal Plant Pathology
• /
• v.14 no.6
• /
• pp.583-588
• /
• 1998

This study was conducted to investigate the potential of nitrate-nonutilizing mutants (nit mutants) in ecological studies of Fusarium disease of strawberry. Nit mutants of Fusarium oxysporum from strawberry were easily formed on chlorate-containing media. Nit mutants were assigned to three phenotypic classes, nit1, nit3, and NitM, on the basis of their growth on media containing one of the following five different nitrogen sources ; nitrate, nitrite, hypoxanthine, ammonium and uric acid. Frequency of nit mutation and proportion of three phenotypes of nit mutants depended on the isolate. Mutation rate was 45.6% and ranged from 15.0% to 95.0%. The frequency of nit1 mutants was higher than that of nit3 or NitM. The complementary reaction between nit1 and NitM was higher than that of other combination. There has been no complementary response observed between nit3 and nit3. The nit mutants showed similar growth pattern as the that of wild type isolate on potato sucrose agar and potato sucrose liquid media. Most of the mutants retained pathogenicity, and maintained their phenotypes even after two year preservation through subculture on slanted PSA at room temperature. Nit mutants were selctively isolated from infested soil and infected plants on the selective medium (MMCPA) containing potassium chlorate with their original phenotypes, while naturally occurring isolates of Fusarium oxysporum were not grow on the medium. On the contrary, nit mutants showed very slight growth on the medium (MMPA) containing nitrate as a sole nitrogen source, and therefore could be distinguished from wild type isolate.

• Asian Journal of Turfgrass Science
• /
• v.25 no.2
• /
• pp.171-176
• /
• 2011

Sclerotinia homoeocarpa, the causal agent of dollar spot, is one of the most common pathogens of cool season turfgrasses in South Korea. The vegetative compatibility group (VCG) assay was carried out using nitrate-nonutilizing (nit) mutants recovered from 13 South Korean isolates with various geographical origins. The mutants were divided into four phenotypic classes based on mutation loci associated with nitrogen assimilation: nit1, nit2, nit3, and NitM. The recovered number of nit mutants greatly varied among the isolates, ranging from 0 to 15 mutants. Of the mutants isolated, nit1 and nit2 mutants were most common (80%) while NitM and nit3 were relatively rare. One dominant and four minor VCGs were determined from 18 mutant isolates tested. To study population structures of Korean S. homoeocarpa isolates and increase our understanding of its ecological and epidemiological aspects for dollar spot management on turfgrass, more generated mutants should be tested with more diverse isolate collections.

• The Plant Pathology Journal
• /
• v.15 no.1
• /
• pp.53-56
• /
• 1999

Fifty-three isolates of Fusarium graminearum were obtained from corn and barley samples in several provinces of Korea. Gas chromatography-mass spectrometric analysis of trichothecenes produced by these isolates revealed that 37 and 16 isolates were nivalenol (NIV)- and deoxynivalenol (DON)-chemotypes, respectively. Two hundred and seventy-five nitrate-nonutilizing (nit) mutants were obtained from the isolates. Of these mutants, 187 were identified as nit1, nit3, or NitM, but 88 could not be identified as one of these classes. The highest frequency of nit mutant was nit1 (65%), followed by nit3 (20%) and NitM (15%). Higher frequency of NitM was observed in DON-chemotypes than in NIV-chemotypes. The mutants were used for vegetative compatibility group (VCG) analysis by examining heterokaryosis using complementary mutant pairs. No heterokaryon formation was observed among all 1,248 pairwise combinations, suggesting that all isolates tested belong to different VCGs. Higher frequency of self-incompatibility was observed in NIV-chemotypes than in DON-chemotypes. These results suggest that the like-lihood of asexual genetic recombination may be very low I F. graminearum under the field condition.

• Korean Journal Plant Pathology
• /
• v.12 no.4
• /
• pp.395-401
• /
• 1996

국내의 고추, 사과, 포도, 스타티스(statice)에서 분리한 Glomerella cingulata 균주들의 병원성과 체세포화 합성군(vegetative compatibility group : VCG)과의 관계를 조사하였다. 사과, 포도, 스타티스에서 분리된 균주들은 전기주에 모드 병원성을 나타내었으나 고추에는 병원성이 없었다. 한편, 고추에서 분리된 균주들은 무상처접종시 병원성을 나타내지 못하였다. Nitrate nonutilizing(nit) mutant는 1.5%의 KClO\ulcorner을 첨가한 최소배지에서 선발하였다. nit mutnat들은 nit1, nit2, nit3, nitM의 4가지 표현형 중 하나에 속하였다. VCG는 표현형이 다른 nit mutan간의 대치배양을 통해 결정하였는데 사과, 포도, 스타티스에서 분리한 균주들간에는 같은 VCG를 나타낸 반면 고추에서 분리된 균주들은 다른 VCG로 나타났다. 따라서 G. cingulata 균주들의 체세포화합성은 병원성과 밀접하게 관련되어 있음을 알수 있었다. 또한 동일한 VCG에 속하며 기주가 다른 균주들의 대치배양시 heterokaryon을 형성했으나 자낭을 형성하지는 않았다.

• 대한정형외과스포츠의학회:학술대회논문집
• /
• 2004.09a
• /
• pp.54-54
• /
• 2004

• The Plant Pathology Journal
• /
• v.16 no.5
• /
• pp.247-251
• /
• 2000

Latent infections of healthy-appearing oaks of Hypoxylon atropunctatum complicates field studies by interfering with inoculation experiments to follow pathogenesis, fungal development and reproduction of this canker rot fungus. Mutants with unique and easily scorable phenotypes would be useful for inoculation studies. There is a broad range in the capacity of wild-type isolates to utilize nitrate as a sole nitrogen sources. Several types of nitrate-nonutilization mutants (nit1, Nit3, NitM) were selected from nitrate-utilizing wild-type isolates. Also, a few mutants of Hypoxylon atropunctatum were selected that could only grow poorly on basal medium supplemented with various nitrogen sources and even on yeast extract agar. These unknown mutants need to be characterized further. Nit mutants of Hypoxylon atropunctatum were readily selected, grew well and were recovered after inoculation into oak stems. These results suggest that nit mutants could be useful for inoculation studies in trees that contain latent infections.

• Journal of Plant Biotechnology
• /
• v.40 no.4
• /
• pp.198-202
• /
• 2013

To produce transgenic cucumber expressing Nit gene coffering abiotic resistance, the cotyledonary-node explants of cucumber (cv. Eunsung) were inoculated with A. tumefaciens transformed with pPZP211 or pCAMBIA2300 carrying Nit gene, that has cis-acting element involved in resistance to various abiotic environmental stresses. After co-cultivation, the procedures of selection, shoot initiation, shoot elongation, and plant regeneration were followed by cotyledonary-node transformation method (CTM, Jang et al. 2011). The putative transgenic plants were selected when shoots were grown to a length greater than 3 cm from the cotyledonary-node explants on selection medium supplemented with 100 mg/L paromomycin as a selectable agent. The confirmation of transgenic cucumber was based on the genomic PCR, Southern blot analysis, RT-PCR, and Northern blot analysis. A 105 shoots (4.12%) selected from the selection mediums were obtained from 2,547 explants inoculated. Of them, putative transgenic plants were only confirmed with 45 plants (1.77%) by genomic PCR analysis. Transgenic plants showed that the Nit genes integrated into each genome of 39 plants (1.53%) by Southern blot analysis, and the expression of gene integrated into cucumber genome was only confirmed at 6 plants (0.24%) by RT-PCR and Northern blot analysis. These results lead us to speculate that the genes were successfully integrated and expressed in each genome of transgenic cucumber.

• The Plant Pathology Journal
• /
• v.30 no.4
• /
• pp.384-396
• /
• 2014

Vegetative compatibility groups (VCGs) are determined for many fungi to test for the ability of fungal isolates to undergo heterokaryon formation. In several fungal plant pathogens, isolates belonging to a VCG have been shown to share significantly higher genetic similarity than those of different VCGs. In this study we sought to examine the relationship between VCG and genetic similarity of an important cool season turfgrass pathogen, Sclerotinia homoeocarpa. Twenty-two S. homoeocarpa isolates from the Midwest and Eastern US, which were previously characterized in several studies, were all evaluated for VCG using an improved nit mutant assay. These isolates were also genotyped using 19 microsatellites developed from partial genome sequence of S. homoeocarpa. Additionally, partial sequences of mitochondrial genes cytochrome oxidase II and mitochondrial small subunit (mtSSU) rRNA, and the atp6-rns intergenic spacer, were generated for isolates from each nit mutant VCG to determine if mitochondrial haplotypes differed among VCGs. Of the 22 isolates screened, 15 were amenable to the nit mutant VCG assay and were grouped into six VCGs. The 19 microsatellites gave 57 alleles for this set. Unweighted pair group methods with arithmetic mean (UPGMA) tree of binary microsatellite data were used to produce a dendrogram of the isolate genotypes based on microsatellite alleles, which showed high genetic similarity of nit mutant VCGs. Analysis of molecular variance of microsatellite data demonstrates that the current nit mutant VCGs explain the microsatellite genotypic variation among isolates better than the previous nit mutant VCGs or the conventionally determined VCGs. Mitochondrial sequences were identical among all isolates, suggesting that this marker type may not be informative for US populations of S. homoeocarpa.

• Proceedings of the Korean Geotechical Society Conference
• /
• 1993.10b
• /
• pp.223-234
• /
• 1993

• Journal of the Korean Society of Marine Environment & Safety
• /
• v.18 no.5
• /
• pp.388-397
• /
• 2012

In this study, 3D-NIT(3-Dimensional Numerical Irregular wave Tank) model in which regular wave as well as stable irregular wave can be generated in 3-dimensional numerical irregular wave tank was proposed. To verify validity, the following steps need to be conducted: 1) comparative analysis between calculated waveforms and targeted waveforms at the wave generating point, 2) comparative analysis with the existing experimental values of overtopping volume estimated, targeting shore protection structures installed on a slope bed, 3) comparison with the existing numerical and hydraulic experimental results through application in the analysis on the wave deformation by structures and wave force acting on the vertical cylindrical structures. Based on the results, characteristics of the breaking wave forces according to incident waves and interval distance of structures were identified through application of 3D-NIT model in the analysis on the breaking wave forces acting on the cylindrical structures installed on a slope bed, and reflection and overtopping was reviewed through application in the special breakwaters on the domestic fields. The numerical results obtained the 3D-NIT model are in good agreement with experimental results, and its applicaion to the complex-shpaed coastal structures is verified.