• The Plant Pathology Journal
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• v.18 no.2
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• pp.57-62
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• 2002

In vivo expression technology (IVET) has been developed to study bacterial gene expression in Salmonella typhimurium during host infection. The expression of selected genes by IVET has been elevated in vivo but not in vitro. The selected genes turned out to be important for bacterial virulence and/or pathogenicity. IVET depends on a synthetic operon with a promoterless transcriptional fusion between a selection marker gene and a reporter gene. The IVET approach has been successfully adapted in other bacterial pathogens and plant-associated bacteria using different selection markers. Pseudomonas putida suppresses citrus root rot caused by Phytophthora parasitica and enhances citrus seedling growth. The WET strategy was adapted based on a transcriptional fusion, pyrBC'-lacZ, in P. putida to study the bacterial traits important far biocontrol activities. Several genes appeared to be induced on P. parasitica hyphae and were found to be related with metabolism and regulation of gene expression. It is likely that the biocontrol strain took a metabolic advantage from the plant pathogenic fungus and then suppressed citrus root rot effectively. The result was parallel with those from the adaptation of IVET in P. fluorescens, a plant growth promoting rhizobacteria (PGPR). Interestingly, genes encoding components for type III secretion system have been identified as rhizosphere-induced genes in the PGPR strain. The type III secretion system may play a certain role during interaction with its counterpart plants. Application of IVET has been demonstrated in a wide range of bacteria. It is an important strategy to genetically understand complicated bacterial traits in the environment.

• Current Research on Agriculture and Life Sciences
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• v.23
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• pp.33-41
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• 2005

Above 130 accessions of pepper consisting of 50 introductions from Mexico and Nepal, and resistant and susceptible controls were tested for resistance to bacterial wilt and to Phytophthora root rot at seedling stage by artificial inoculation. Aa the results, KC897, KC939, KC936 were newly found resistant to bacterial wilt in addition to already known resistance sources such as KC126, KC350, KC351, KC353. No new sources of resistance to Phytophthora root rot were found among the introductions from Mexico and Nepal.

• Korean Journal of Environmental Agriculture
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• v.25 no.3
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• pp.228-235
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• 2006

Pseudomonas aeruginosa $GRC_2$, siderophore-producing strain, inhibited growth of Macrophomina phaseolina in vitro and reduced charcoal rot in seeds of Brassica juncea in field when coated with adaptive strains. P. aeruginosa $GRC_2$ and Azotobacter chroococcum $AC_1$ produced indole-3-acetic acid and solubilized insoluble phosphate. A. chroococcum $AC_1$ fixed nitrogen asymbiotically. Urea and diammonium phosphateadaptive variant strains of P. aeruginosa and A. chroococcum strongly inhibited M. phaseolina in comparison to parental strains. Bacterization of seeds induced seed germination, seedling growth, and enhanced yield of B. juncea by 10.87% as compared to full doses of urea and diammonium phosphate. Both adaptive strains of chemical fertilizers aggressively colonized roots, showing effectiveness to growth and developments of B. juncea.

• Journal of Ginseng Research
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• v.26 no.3
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• pp.151-158
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• 2002

Ginseng (Panax quinquefolius L.) has become one of the most valuable herb crops grown in North America. However, traditional cropping practices are favourable to disease and significant losses due to root disease are common, despite frequent use of fungicides. Seedlots are often contaminated with pathogens, however, little is known about the causes of seed decay and the role of seed pathogens as incitants of root rots. It was shown that both Fusarium spp. and Cylindrocarpon destructans were able to rot seeds and that C. destructans was more virulent than Fusarium spp. on seedling roots. A modified rose bengal agar MRBA) medium (1 g KH$_2$PO$_4$; 0.5 g MgSO$_4$; 50 mg rose bengal; 10 g dextrose; 5 g Bacto peptone; 15 g Bacto agar; 30 mg streptomycin sulfate; 250 mg ampicillin; 10 mg rifampicin; 500mg pentachloronitrobenzene; 500 mg dicloran; and 1 L distilled water) was superior to potato dextrose agar in detecting C. destuctans in diseased roots. Isolation of C. destructans from diseased seedlings arising from seeds sown in replant soil supported the hypothesis that this pathogen is a cause of ginseng replant failure in North America.

• The Korean Journal of Mycology
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• v.49 no.4
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• pp.441-454
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• 2021

Fungal diseases including anthracnose, stem rot, blight, wilting, and root rot of crops are caused by phytopathogens such as Colletotrichum species, Sclerotinia sclerotiorum, Phytophthora species, and Fusarium oxysporum and F. solani which threaten the production of chili pepper. In this study, to identify biological control agents (BCAs) of phytopathogenic fungi, potentially useful Bacillus species were isolated from the field soils. We screened out five Bacillus strains with antagonistic capacity that are efficiently inhibiting the growth of phytopathogenic fungi. Bacillus species were characterized by the production of extracellular enzymes, siderophores, and indole-3-acetic acid (IAA). Furthermore, the influence of bacterial strains on the plant growth promoting activity and seedling vigor index were assessed using Brassica juncea as a model plant. Inoculation with Bacillus subtilis SRCM 121379 significantly increased the length of B. juncea shoots and roots by 45.6% and 52.0%, respectively. Among the bacterial isolates, Bacillus subtilis SRCM 121379 showed the superior enzyme activities, antagonistic capacity and plant growth promoting effects. Based on the experimental results, Bacillus subtilis SRCM 121379 (GenBank accession no. NR027552) was finally selected as a BCA candidate.

• Korean Journal of Medicinal Crop Science
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• v.9 no.3
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• pp.211-219
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• 2001

The disease incidence rates of Phytophthora root rot of A. macrocephala caused by P. drechsleri were dramatically increased in two distinctive periods at experimental fields of National Crop Experiment Station(NCES), Suwon, in 1999 and in 2000 ; one was in the period of 30 to 45 days old seedling stage in spring and the other was just after heavy rainy season in late summer or in early fall. The disease was occurred at seedling stage under the conditions of ${{\geq}15^{\circ}C}$ of average temperature with ${{\geq}100mm}$ rainfalls for 20 days and the tendencies were similar in both year. By the disease, rhizome propagated field was more damaged(18.6%) than seed propagated field(56.0%). Comparing the disease incidence rates at five different fields in Suwon, Youngju and Andong, the damages at soil improving fields and non-mulching fields were less severe than those at continuous cropping fields without soil improvement and mulching fields and occurrence. Expansion of the disease were seemed to be highly related with the populations of P. drechsleri in soils depend on the cultivation method and field conditions. Although the populations of the pathogen in soils collected from Andong and Youngju, in which rhizome were continuously propagated for two and three years respectively, were comparably less than that from Suwon, in which rhizome were propagated for one year, however, the damages by the disease were more severe in Andong and Youngju. So, two or more years of cultivation at the same field may not be useful for Atractylodes plants..

• Journal of Ginseng Research
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• v.30 no.2
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• pp.78-81
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• 2006

Freshly harvested, immature (green) seeds of North American ginseng (Panax quinquefolius L.) were stratified for up to 3 years in plastic pails in controlled environment rooms at $5{\pm}1^{\circ}C$ for 9 months and then $21{\pm}2^{\circ}C$ for 3 months (Trt. 1, regular stratification), or continuously at $-2{\pm}0.2^{\circ}C$ (Trt. 2), or continuously at $3{\pm}0.2^{\circ}C$ (Trt. 3). During stratification at -2 and $3^{\circ}C$ embryos did not grow. On seeding in the field embryos grew rapidly and resultant seedlings were comparable to those from regularly stratified seed. Seedling emergence rate was acceptable at the industry expected rate of 68% after one year of storage, but not after two years storage when it declined to 17.5%. Seed rot was so severe in year 3 that no planting was carried out. Seedling and second year growth were similar at the three stratification temperatures; most importantly, root dry weight (economic yield) was similar. Low-temperature storage of freshly-harvested North American ginseng seed is an acceptable method for short-term retention of propagating material.

• Korean Journal Plant Pathology
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• v.13 no.3
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• pp.152-159
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• 1997

Six pathogenic Pythium isolates obtained from diseased ginger rhizomes were identified as Pythum myriotyrum Drechsler based on various morphological and physiological characteristics. The isolates showed strong virulence on underground parts of buds, crowns, rhizomes, roots and aerial parts of leaves and stems as well. The isolates caused rot of germinated seeds of 10 different crops tested, including cucumber and pepper, and markedly inhibited seedling growth of 3 crops tested, including corn and barley. Maximum, optimum and minimum growth temperatures for P. myriotylum were 39~45$^{\circ}C$, 33~37$^{\circ}C$ and 5~7$^{\circ}C$, respectively. Optimum pH for the growth was 6~7. Mycelial linear growth was most rapid on V-8 juice agar, but aerial mycelia were most abundant on PDA and corn meal agar. Zoosporangial and oogonial formation was greatest on V-8 juice agar. Optimum temperatures for the production of zoosporangia and oogonia were 20~35$^{\circ}C$ and 15$^{\circ}C$, respectively.

• International Journal of Industrial Entomology and Biomaterials
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• v.31 no.2
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• pp.107-114
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• 2015

Endophytes provide multifarious benefits such as promotion of plant growth and yield, suppression of phyto-pathogens, phosphate solubilising and fixation nitrogen. A study has been carried out to explore growth promotion and antifungal activities of endophytes of mulberry (Morus spp.). Endophytic bacteria were isolated from mulberry plants and studied their cultural, morphological characters, growth promotion as well as their antifungal activity against Rhizoctonia bataticola and Fusarium oxysporum , two mulberry root rot associated pathogens. Except two isolates, all bacteria were colourless and the colony size of eight isolates was small. The margin of five isolates was irregular and the consistency of three isolates was creamy, six isolates was slimy and one was mucoid. Texture of seven isolates was convex and others were flat. Eight isolates were gram positive and the rest Gram negative, five were cocci and others were bacilli (rod shaped). Four isolates were motile and all were catalase positive and only three isolates were oxidase positive. Spore staining was positive only for two isolates. The growth promotion study showed that there was significant difference in root length and seedling length. The antagonistic effect of the bacterial isolates was tested against R. bataticola showed significant (p <0.05) influence of the bacteria, days after inoculation and their interaction on the inhibition of fungal growth. The isolate En-7 completely inhibited the fungus followed by En-5 (66.67%). The bacterial isolates significantly (p <0.05) inhibited growth of F. oxysporum in PDA. The mean inhibition was higher (70.45%) in case of En-7 followed by En-8 (68.65%) and En-10 (66.44%). The study reveals that some endophytic bacteria associated with mulberry have growth promotion and antifungal activity and could be explored for promotion of mulberry growth and managing root rot disease.

• The Plant Pathology Journal
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• v.32 no.5
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• pp.396-406
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• 2016

Continuous supplementation of mineral nutrients and salicylic acid (SA) as foliar application could improve efficacy in controlling basal stem rot (BSR) disease in oil palm seedling. It is revealed from the results that the highest disease severity index (58.3%) was recorded in T8 treatments at 9 months after inoculation. The best disease control was achieved by T7 treatments (calcium/copper/SA [Ca/Cu/SA]) (5.0%) followed by T1 (5.5%), T5 (5.8%), T3 (8.3%), T6 (8.3%), T4 (13.3%), and T2 (15.8%) treatments. Continuous supplementation of Ca/Cu/SA was found to be the most effective in controlling the disease and the high performance liquid chromatography results showed the detection of ergosterol at very low concentration in the treated samples. Moreover, the transmission electron microscopy analysis results clearly indicated that T7 treatment was also enhancing lignification, which was responsible for the thickness of the secondary cell walls and middle lamella compared to untreated samples. It was therefore, concluded that continuous supplementation of minerals nutrients and SA could effectively suppress disease severity by reducing ergosterol activity and also improve the process of lignification in the treated plants. Furthermore, this treatment also managed to delay the onset of BSR symptoms and promote the growth of the seedlings and eventually suppress the BSR disease.