cDNAs complementary to the 3'-terminal regions of two potyvirus genomes were cloned and sequenced. The clone G7 contains one open reading frame (ORF) of 1,338 nucleotides and a 3' untranslated region (3'-UTR) of 403 nucleotides at the 3'-end excluding the 3'end poly(A) tail. The putative viral coat protein (CP) shows 55%-92% amino acid sequence homology to those of Allium potyviruses. The genome size of the virus was analyzed to be about 9.0 kb by Northern blot analysis. Five cDNA clones were screened out using GPV2 oligonucleotide as a probe. One of these clones, DEA72, which has a longest cDNA insert, contains one ORF of 1,459 nucleotides and a 3'-UTR of 590 nucleotides at the 3'-end excluding the 3'-end poly(A) tail. The putative viral CP shows 57%-88% amino acid sequence homologies to those of Allium potyviruses. The genome size of the virus was analyzed to be about 9.6 kb by Northern blot analysis. The results of immunoblot and Northern blot analyses suggest that almost all of the tested garlic plants showing mosaic or streak symptoms are infected with DEA72-potyvirus in variable degrees but rarely infected with G7-potyvirus in variable degrees but rarely infected with DEA72-potyvirus in variable degrees but rarely infected with G7-potyvirus. Immunoelectron microscopy using anti-DEA72 CP antibody shows that this potyvirus is about 750 nm long and flexuous rod shaped.

Lichen-forming (LFF) or lichenicolous fungi (LCF) were isolated from the lichens collected at‘Backwoon’mountain area,‘Chiri’mountain area and‘Sorok’island in the southern regions of Korea and were screened for antagonistic efficacy against several phyto-pathogenic fungi. Symbiotic algae-free LFF and LCF were isolated by the following methods: I) discharged spores (ascospores), II) macerated thallus suspension and III) direct use of thallus fragments. Among 58 isolates obtained from 34 lichens, 8 isolates showed antifungal activity against Rhizoctonia solani. Antifungal activities of the strongest antagonistic isolate (LB9810) originated from the thallus of Parmelia quercina lichen were evaluated against 15 phyto-pathogenic fungi. When crude methanol extract of mycelia of the LB8910 isolate was employed at the rate of 0.5% (v/w), fungal growth of Magnaporthe grisea and Rhizoctonia solani was severly and Rhizoctonia solani was severly inhibited as much as approximately 60% compared to control. Growth of various food-borne same extract. The extract was successively partitioned with n-hexane, ethyl acetate and n-butanol. n-Hexane fraction displayed the strongest antifungal activities against R. solani. The LB9810 isolate was finally identified as Fusarium equiseti (Corda) Sacc., which has not been reported as LFF or LCF yet. Therefore, it is very likely that F. equiseti isolated it the study was originated from the contaminants associated with thallus fragments rather than from LFF or LCF.

A technique based on the polymerase chain reaction (PCR) for the specific detection of genus Phytophthora and Phytophthora cryptogea-P. drechsleri complex group was developed using nucleotide sequence information of ribosomal DNA (rDNA) regions. The internal transcribed spacers (ITS) including 5.8S were sequenced for P. cryptogea-P. drechsleri complex group and its related species. Two pairs of oligonucleotide primers were designed. Primer pair ITS1/Phy amplified ca. 240 bp fragment in 12 out of 13 specie of Phytophthora, but not in Pythium spp., Fusarium spp.and Rhizoctonia solani. Primer pair rPhy/Pcd amplified 549 bp fragment only in P. cryptogea-P. drechsleri complex group, but not in other Phytophthora spp.and other genera. Specific PCR amplification using the primers was successful in detecting Phytophthora and P. cryptogea-P. drechsleri complex group in diseased plants.

Many of plant defense responses are consequence of transcriptional activation of related genes. We have developed a modified differential screening procedure to isolate tobacco genes that are involved in the defense responses against TMV infection. A cDNA library was constructed from Nicotiana glutinosa leaves infected by TMV under temperature shift conditions. Each of plasmid DNA in the library was hybridized on a set of slot blots to a pool of cDNA probes prepared from either TMV-infected or mock-treated tobacco leaves. Among 900 plasmid DNAs, 81 clones exhibiting significantly enhanced or reduced level of hybridization to either probe were selected for nucleotide sequencing. The clones were listed into 61 genes considering redundancy between the sequences. The genes were identified to be defense-related genes including PR-genes and genes involved in primary or secondary metabolisms. This results supports the implication that plant defense process entails a major shift in total cellular metabolisms rather than activation of a limited number of defense-related genes. Expression patterns of a number of defense-related genes. Expression patterns of a number of selected genes were examined in northern blot analyses. It is notable that the clone 630 of unknown function exhibits expression pattern similar to those of previously known PR-genes. Experiments to elucidate the roles in defense mechanism of a couple of genes newly identified in this study are in progress.

Occurrence of soft rots was observed on Dendrobium phalaenopsis and Phalaenopsis sp. that were grown at the greenhouses in Sunchon and Kwangyang areas, Chonnam province of Korea in 1997 and 1998. Typical soft rot symptom appeared frequently on young plants of D. phalaenopsis and Phalaenopsis sp. Soft rot symptom usually appeared on old leaves of D. phalaenopsis, and extended into whole leaves, accompanying blighting of whole plants. Symptom began as a small water-soaked lesion on old leaves of Phalaenopsis sp., which enlarged rapidly on the leaves and eventually resulted in soft rots of whole plants. The causal organism isolated from the infected lesions was identified as Erwinia chrysanthemi based on its pathogenicity, physiological and biochemical characteristics, and the results of the BIOLOGTM program. The bacterial soft rot caused by e. chrysanthemi was firstly describe din D. phalaenopsis and Phalanopsis sp. in Korea.

A fungus associated with gray blight on tea plant (Camellia sinensis) was identifed as Pestalotiopsis theae based on the mycological characteristics. Mycelial growth on potato dextrose agar and size and shape of conidia of P. theae were similar to those of P. longiseta, but P. theae was different from P. longiseta in the color of three median cells and the number of apical appendages. Artificial inoculation of conidial suspension or mycelial mats on the wounded leaves and shoots of healthy plants induced the same disease, respectively. The Korean native variety was relatively. The Korean native variety was relatively more resistat to P. theae than a Japanese variety‘Yabukita’which has bee recently introduced and planted in large areas of southern parts of Korea. Here, we report the report the first record of gary blight caused by P. theae on tea plant in Korea.