Byung-Sup Kim

Enterobacter pyrinus sp. nov., an Organism Associated with Brown Leaf Spot Disease of Pear Trees

A new species, Enterobacter pyrinus, which was isolated from brown leaf spot lesions on pear trees, is described on the basis of the characteristics of seven strains. These bacteria are gram-negative, facultatively anaerobic, straight rods (0.6 to 1.0 by 1.6 to 2.3 μm) that are motile and peritrichous. As determined by DNA hybridization (hydroxyapatite method), these seven strains were 97.5% related in both 60 and 75°C reactions, with no evidence of sequence divergence, indicating that they are members of a single species. E. pyrinus is most closely related to Enterobacter gergoviae (46%) and to Enterobacter agglomerans hybridization group XI (37%). E. pyrinus is differentiated from E. gergoviae by its growth in KCN broth, acid production from myo-inositol, and lack of acid production from raffinose. The type strain of E. pyrinus is strain KCTC 2520 (= CDC G6570 = ATCC 49851).

Biocontrol of Fusarium Crown and Root Rot and Promotion of Growth of Tomato by Paenibacillus Strains Isolated from Soil

Abstract In this study, bacterial strains were isolated from soils from 30 locations of Samcheok, Gangwon province. Of the isolated strains, seven showed potential plant growth promoting and antagonistic activities. Based on cultural and morphological characterization, and 16S rRNA gene sequencing, these strains were identified as Paenibacillus species. All seven strains produced ammonia, cellulase, hydrocyanic acid, indole-3-acetic acid, protease, phosphatase, and siderophores. They also inhibited the mycelial growth of Fusarium oxysporum f. sp. radicis-lycopersici in vitro. The seven Paenibacillus strains enhanced a range of growth parameters in tomato plants under greenhouse conditions, in comparison with non-inoculated control plants. Notably, treatment of tomato plants with one identified strain, P. polymyxa SC09-21, resulted in 80.0% suppression of fusarium crown and root rot under greenhouse conditions. The plant growth promoting and antifungal activity of P. polymyxa SC09-21 identified in this study highlight its potential suitability as a bioinoculant.

Antifungal Activity of Paenibacillus kribbensis Strain T-9 Isolated from Soils against Several Plant Pathogenic Fungi

The bacterial strain T-9, which shows strong antifungal activity, is isolated from the soils of Samcheok, Gangwondo and identified as Paenibacillus kribbensis according to morphological and taxonomic characteristics and 16S rRNA gene sequence analysis. The P. kribbensis strain T-9 strongly inhibits the growth of various phytopathogenic fungi including Botrytis cinerea, Colletotricum acutatum, Fusarium oxysporum f. sp. radicis-lycopersici, Magnaporthe oryzae, Phytophthora capsici, Rhizoctonia solani, and Sclerotium cepivorum in vitro. Also, the P. kribbensis strain T-9 exhibited similar or better control effects to plant diseases than in fungicide treatment through in vivo assays. In the 2-year greenhouse experiments, P. kribbensis strain T-9 was highly effective against clubroot. In the 2-year field trials, the P. kribbensis strain T-9 was less effective than the fungicide, but reduced clubroot on Chinese cabbage when compared to the control. The above-described results indicate that the strain T-9 may have the potential as an antagonist to control various phytopathogenic fungi.

Physiological Races of Phytophthora infestans in Korea

A total of the 261 Phytophthora infestans isolates collected from 2003 to 2005 in Korea were investigated for their physiological race composition. Among the isolates, we detected 18 physiological races and the dominant races were R0.1.3.5.6.10.11 and R0.1.3.5.6.7.10.11 with frequencies of 18.4% and 11.4%, respectively. All of the P. infestans races carried multiple virulence genes and showed virulence to the potato resistance genes R1, R3, R5, R6, R7, R10 and R11, but not to R8 and R9. Therefore, it is likely that the physiological races of P. infestans were diverse in Korea.

The Race Differentiation of Phytophthora capsici in Korea

This study was examined to identify the race differentiation and distribution of mating type on Phytophthora capsici population in Korea. One hundred forty three isolates of P. capsici were collected from several locations of Korea in 2005-2007. In 2005, 20 isolates of P. capsici were collected and surveyed as A1 mating type of 75% and A2 mating type of 25%. In 2006, a total of 91 isolates were collected and separated as A1 mating type of 49.0%, A2 mating type of 42.9% and S type (sterile) of 3.3%. Isolates obtained in 2007 were similar to 2006 results. Totally, ratio of mating type of 153 isolates was confirmed that A1 type was 56.6%, A2 type was 39.2%, and S type was 4.2%. Thirteen pepper cultivars with different pathogenic response to 3 typical isolates having different mating were screened among 50 pepper cultivars and determined as race differential cultivars for investigation. The 11 races of P. capsici were found by using 13-race differential cultivars. These results indicated that at least 11 races of P. capsici are existed and confirmed race differentiation of P. capsici in pepper.

Survey of Fungicide Resistance for Chemical Control of Botrytis cinerea on Paprika

Four hundred and sixty six isolates of B. cinerea were obtained from infected leaves, stems and fruits of paprika grown in greenhouses or plastic film houses in Gangwon province, Korea, between August and November in 2006 and 2007. These isolates were classified into five representative phenotypes of resistant (R) and sensitive (S) reactions as SSR, SRR, RSS, RRS and RSR according to the responses of isolates against benzimidazole, dicarboximide and N-phenylcarbamate fungicide in order. The percentage of five phenotypes were 51.3, 2.4, 35.6, 8.1 and 2.6%, respectively. The SSR phenotype (51.3%) was the most common. Among the nineteen fungicide products evaluated to compare their efficacy against gray mold pathogen on the paprika fruit inoculated with fungal mycelia, the mixture of diethofencarb and carbendazim was the most effective followed by iprodione, boscalid, the mixture of iprodione and thiophanate-methyl, fludioxonil, polyoxin-B, fluazinam, the mixture of tebuconazole and tolyfluanid and procymidone; while in the assay methods inoculated with fungal spores, the mixture of tebuconazole and tolyfluanid was the most effective in controlling gray mold followed by boscalid, fludioxonil, the mixture of diethofencarb and carbendazim and the mixture of pyrimethanil and chlorothalonil.

Evaluation of Paenibacillus polymyxa strain SC09-21 for biocontrol of Phytophthora blight and growth stimulation in pepper plants

We assessed the efficacy of Paenibacillus polymyxa strain SC09-21 for reducing Phytophthora blight (caused by Phytophthora capsici) in pepper plants, and its ability to enhance plant growth. The results of in vitro studies indicated that SC09-21 effectively reduced the radial growth of eight plant pathogens in dual culture, and exerted the maximum antifungal activity against P. capsici. SC09-21 produced ammonia, cellulase, indole-3-acetic acid, protease, and siderophores, and solubilized calcium phosphate. Compared to the control, SC09-21 significantly (P = 0.05) reduced Phytophthora blight severity in pepper plants. After treatment with SC09-21, pepper leaves showed an increase in phenylalanine ammonia lyase (PAL), peroxidase (PO), polyphenol oxidase (PPO), and superoxide dismutase (SOD) activities. PAL, PPO, PO, and SOD activities were higher in treated seedlings than in untreated control. In addition, SC09-21 treatment enhanced pathogenesis-related (PR) protein gene expression in pepper plants, including those of CaPR4 and CaChi2, in the absence of P. capsici. Thus, SC09-21 enhanced different growth parameters. These results indicate that SC09-21 induces a defensive response against P. capsici and promotes growth in pepper plants. Therefore, it could be used as a potential agent for the biological control and growth promotion of plants.

Selection of Desirable Cultivar for Organic Cultivation of Carrot

This research was carried out to selection of desirable cultivar for organic cultivation of carrot in Korea. The assay of disease resistance, insect tolerance and rate of bolting were investigated on 32 cultivars of genetic resources of carrot. This experiment was carried out at experimental field and greenhouse of Gangneung-Wonju National University. `PI 223360` was resistant against powdery mildew. Ten cultivars including `Oxheart Carrot Heirloom` were moderately resistant, 22 cultivars including `Long Impeator #58` were susceptible to powdery mildew. Although there was no resistant cultivar against black rot and leaf blight, our results showed that several cultivars have moderate resistance. Thirteen cultivars including `Oxheart Carrot Heirloom` were having insect (Erythroplusia pyropia) tolerance and `SA 102` and `Scarlet Keeper Carrot Rare` were susceptible. According to the investigation of bolting, 6 cultivars including `Hongsim Ouchon Carrot` were early bolting and 4 cultivars including `Japanese Imperial Long Carrot` were moderate bolting. Other cultivars were identified as late bolting. From above results, we confirmed that `Oxheart Carrot Heirloom` was suitable cultivar for organic cultivation among 32 genetic resources of carrot.

Evaluation of Tomato Genetic Resources for the Development of Resistance Breeding Lines against Late Blight

Department of Plant Science, Gangneung-Wonju National University, Gangneung 210-702, Korea(Received on January 12, 2012; Revised on February 13, 2012; Accepted on March 2, 2012)Occurrence of tomato late blight (Phytophthora infestans) has caused significant losses in tomato yield in allover the world. Evaluation of the level of resistance in tomato gene resources for main breeding and initiationof the resistance breeding program are important for control of this disease. Resistant assay of 78 tomatocultivars/lines to late blight in pots and field experiment was carried out under controlled and naturalconditions in 2009. All commercial cultivars including ‘Legend’ were susceptible. However, 10 lines includingKNU-2, KNU-6-1, KNU-11, KNU-13, KNU-14-1 lines distributed from University of California, Riversideand L3708, AV107-4×L3708, 07-15×L3708, BS67

Changes in the Sensitivity to Metalaxyl, Dimethomorph and Ethaboxam of Phytophthora infestans in Korea

Changes of control efficacy of chemical to potato late blight caused by Phytophthora infestans in potato fields from 2001 to 2004 were examined. Control efficacy of metalaxyl was suddenly decreased from 100% in 2002 to 50% in 2004 and that of dimethomorph also was similar to those of metalaxyl. However, the control efficacy of ethaboxam no great change. Both A1 and A2 mating type isolates were isolated from 2001 to 2004 in several areas in Korea. The majority of the P. infestans isolates were A1 mating type. Total 939 isolates of P. infestans obtained from several areas in Korea from 2001 to 2004 were examined for changes of sensitivity to metalaxyl. Frequencies of metalaxyl resistance isolates were gradually increased from 17% in 2001 to 84.2% in 2004, but isolation frequencies of metalaxyl sensitive and intermediate resistant isolate were decreased. Cause of decreasing control efficacy of metalaxyl was thought by increase of resistance isolates in A1 mating type population according to increasing metalaxyl use. Most isolates were grown at 0.5 /ml of dimethomorph and isolates grown at 1 /ml of dimethomorph were approximately 10.2-22.9%. However, no isolate was able to grow at 5.0 /ml. Based on these results, minimum inhibitory concentrations (MIC) of dimethomorph to P. infestans were determined to be 0.5-1.0 /ml. Our results indicated that the reason decreasing control efficacy of dimethomorph was not caused by occurrence of resistant isolates. About 5% and 12.1% isolates among the total isolates collected in 2003 and 2004 were grown on V-8 juice rye agar containing 1.0 /ml ethaboxam. The 2.1 and 25.4% isolates had MICs of 0.2-0.4 /ml, and MIC values of 87.9% and 74.3% isolates were less than 0.2 /ml concentrations of ethaboxam. Therefore, resistance development by P. infestans to ethaboxam is not likely to occur in the natural condition.