• Current Research on Agriculture and Life Sciences
• /
• v.28
• /
• pp.17-23
• /
• 2010

Selection procedures for breeding genic male sterile lines for resistance to both Phytophthora blight caused by Phytophthora capsici and bacterial spot caused by Xanthomonas euvesicatoria were executed to $F_3$ and $F_4$ generations derived from a cross between a Phytophthora resistant genic male sterile (GMS) breeding line and a bacterial spot and Phytophthora resistant breeding line. Resistance to P. capsici was originally introduced from KC294(CM334) and KC263(AC2258), the well-known sources of resistance to P. capsici. Resistance to bacterial spot was introduced from KC47(PI244670). GMS lines with high resistance to P. capsici were obtained and the selected lines are expected to be quantitatively resistant also to bacterial spot.

• Current Research on Agriculture and Life Sciences
• /
• v.18
• /
• pp.19-25
• /
• 2000

$F_2$ populations of the crosses KC47-1 (PI244670) ${\times}$ KCB14-2-2-3-2 (PI201234), KC220-1 ${\times}$ KC268 and $F_3$ bulk populations of the crosses KC47-1${\times}$KC263 (AC2258), KC47-1${\times}$KCB13-2-1 (PI201232), KC47-1${\times}$KCB13-4-2 (PI201232), either one parent of which was resistant to Phytophthora blight, were tested for both gray leaf spot and Phytophthora blight by serial inoculation with Stemphylium solani or a mixture of S. solani and S. lycopersici, and P. capsici in 1999. In 2000, $F_3$ and $F_4$ lines or populations developed from the respective $F_2$ or $F_3$ selections in the previous year were evaluated for resistance to both diseases. A significant progress in resistance to both diseases was achieved by selection.

• Journal of Microbiology and Biotechnology
• /
• v.26 no.9
• /
• pp.1542-1550
• /
• 2016

This is the first report that paromomycin, an antibiotic derived from Streptomyces sp. AG-P 1441 (AG-P 1441), controlled Phytophthora blight and soft rot diseases caused by Phytophthora capsici and Pectobacterium carotovorum, respectively, in chili pepper (Capsicum annum L.). Chili pepper plants treated with paromomycin by foliar spray or soil drenching 7 days prior to inoculation with P. capsici zoospores showed significant (p < 0.05) reduction in disease severity (%) when compared with untreated control plants. The disease severity of Phytophthora blight was recorded as 8% and 50% for foliar spray and soil drench, respectively, at 1.0 ppm of paromomycin, compared with untreated control, where disease severity was 83% and 100% by foliar spray and soil drench, respectively. A greater reduction of soft rot lesion areas per leaf disk was observed in treated plants using paromomycin (1.0 μg/ml) by infiltration or soil drench in comparison with untreated control plants. Paromomycin treatment did not negatively affect the growth of chili pepper. Furthermore, the treatment slightly promoted growth; this growth was supported by increased chlorophyll content in paromomycin-treated chili pepper plants. Additionally, paromomycin likely induced resistance as confirmed by the expression of pathogenesis-related (PR) genes: PR-1, β-1,3-glucanase, chitinase, PR-4, peroxidase, and PR-10, which enhanced plant defense against P. capsici in chili pepper. This finding indicates that AG-P 1441 plays a role in pathogen resistance upon the activation of defense genes, by secretion of the plant resistance elicitor, paromomycin.

• Journal of Microbiology and Biotechnology
• /
• v.15 no.5
• /
• pp.1001-1010
• /
• 2005

Bacillus megaterium KL39, an antibiotic-producing plant growth promoting rhizobacterium (PGPR), was selected from soil. The antifungal antibiotic, denoted KL39, was purified from culture filtrate by column chromatography using Dion HP-20, Silica gel, Sephadex LH-20, and prep-HPLC. Thin layer chromatography, employing the solvent system of ethanol:ammonia:water=8:1:1, showed the $R_{f}$. value of 0.32. The antibiotic KL39 showed a negative reaction with ninhydrin solution, positive with iodine vapor, and also positive with Ehrlich reagent. It was soluble in methanol, ethanol, butanol, and acetonitrile, but insoluble in chloroform, toluene, hexane, ethyl ether, or acetone. Its UV spectrum had the maximum absorption at 208 nm. Amino acid composition, FAB-mass, $^{1}H-NMR,\;^{13}C-NMR$, and atomic analyses showed that the antibiotic KL39 (MW=1,071) has a structure very similar to iturin E. The antibiotic KL39 has a broad antifungal spectrum against a variety of plant pathogenic fungi including Rhizoctonia solani, Pyricularia oryzae, Monilinia froeticola, Botrytis cinenea, Altenaria kikuchiana, Fusarium oxysporum, and F. solani. An MIC value of $10\;{\mu}g/ml$ was determined for Phytophthora capsici. Macromolecular incorporation studies with P. capsici using radioactive [$^{3}H-adenine$] as the precursor, indicated that the antibiotic KL39 strongly inhibits the DNA biosynthesis of the fungal cell. Microscopic observation of the antifungal action showed abnormal hyphal swelling of P. capsici. The purified antibiotic KL39 was very effective for the biocontrol of in vivo Phytophthora-blight disease of pepper.

• The Plant Pathology Journal
• /
• v.21 no.1
• /
• pp.64-67
• /
• 2005

The biocontrol agent Serratia plymuthica A21-4 readily colonized on the root of pepper plant and the bacterium moves to newly emerging roots continuously. The colonization of A21-4 on the pepper root was influenced by the presence ofPhytophthora capsici in the soil. When P. capsici was introduced in advance, the population density of A21-4 on the root of pepper plant was sustained more than $10^6$ cfu/g root until 3 weeks after transplanting. On the other hand, in the absence of P. capsici, the population density of A21-4 was reduced continuously and less than $10^5$ cfu/g root at 21 days after transplanting. S. plymuthica A21-4 inhibited successfully the P. capsici population in pepper root and rhizosphere soil. In the rhizosphere soil, the population density of P. capsici was not increased more than original inoculum density when A21-4 was treated, but it increased rapidly in non-treated control. Similarly, the population density of P. capsici sharply increased in the non-treated control, however the population of P. capsici in A21-4 treated plant was not increased in pepper roots. The incidence of Phytophthora blight on pepper treated with A21-4 was 12.6%, while that of non-treated pepper was 74.5% in GSNU experimental farm experiment. And in farmer's vinyl house experiment, the incidence of the disease treated with the fungicide was 27.3%, but treatment of A21-4 resulted in only 4.7% of the disease incidence, showing above 80% disease control efficacy.

• The Plant Pathology Journal
• /
• v.20 no.1
• /
• pp.63-66
• /
• 2004

Ginseng (Panax ginseng) is one of the most widely cultivated medicinal herbs in Korea. However, yield losses reached up to 30-60％ due to various diseases during 3 or 5 years of ginseng cultivation in the country. Therefore, successful production of ginseng roots depends primarily on the control of diseases. The objective of this study was to select potential biocontrol agents from rhizobacteria isolated from various plant internal root tissues for the control of multiple ginseng diseases as an alternative to fungicides. Among 106 Bacillus strains, two promising biocontrol agents, Bacillus pumilus strain B1141 and Paenibacillus lentimobus strain B1146, were selected by screening against root rot of ginseng caused by Cylindrocarpon destructans in a greenhouse. Pre-inoculation of selected isolates to seed or l-year-old root of ginseng resulted in stimulation of shoot and/or root growth of seedlings, and successfully controlled root rot caused by C. destructans (P<0.05). Furthermore, drenching of cell suspension of the selected isolates on seedling-growing pots reduced the incidence of Phytophthora blight after the seedlings were challenged with zoospores of Phytophthora cactorum (P<0.05). P. lentimorbus strain B1146 showed antifungal activity against various soil-borne pathogens in vitro, while B. pumilus strain B1141 did not show any. Results of this study suggest that some rhizobacteria can induce resistance against various plant diseases on ginseng.

• Research in Plant Disease
• /
• v.12 no.1
• /
• pp.46-50
• /
• 2006

The microorganisms with the antifungal activity against Phytophthora capsici and Colletotrichum acutatum and the plant growth-promoting activity were screened from a forest and natural fields of Gajang-Dong, Sangju-city. One of the isolates, Streptomyces griseofuscus 200401, was selected as a good plant growth-promoting strain in this study. In greenhouse test, the number of leaf, fresh weight, and dry weight of pepper plants, that were grown with treatment of culture suspension or powder containing S. griseofuscus 200401, were higher than those without the bacterial cells. Cultivation of S. griseofuscus 200401 strain for 7 days in a nutrient rich medium produced ammonium chloride up to 0.13 ${\mu}g/ml$ in the culture solution of S. griseofuscus. Treatment of the selected strain significantly reduced the severity of the late blight of pepper plants to show the equivalent disease control activity to chemical fungicide. This study suggests that S. griseofuscus 200401 strain could be a potential biological agent with the biocontrol activity and the plant growth-promoting activity.

• Research in Plant Disease
• /
• v.8 no.3
• /
• pp.131-145
• /
• 2002

• The Plant Pathology Journal
• /
• v.17 no.1
• /
• pp.9-21
• /
• 2001

No Abstract.See Full-text

• Journal of Microbiology and Biotechnology
• /
• v.13 no.3
• /
• pp.415-421
• /
• 2003

A bacterium, Pseudomonas fluorescens 2112, that is antagonistic against a red-pepper blight-causing fungus, Phytophthora capsici, was isolated from the local soil of Gyongju, Korea. This strain formed an orange-colored clear halo zone on chrome azurol S (CAS) blue agar, suggesting the production of a siderophore in addition to an antifungal antibiotic. The optimal culture conditions for siderophore production by P. fluorescens 2112 were 30-h cultivation at $25^{\circ}C$ and pH 6.5 in King's B medium. The presence of $20{\mu}g/ml\;of\;Fe^3+$ ion or EDDHA promoted the production of siderophore in King's B medium. The siderophore was purified from culture broth by CM-Sephadex C-25 and Sephadex G-25 column chromatographies. The UV spectra of the purified siderophore was the same as that of pyoverdins or pseudobactins. The molecular mass was 1,958 Da determined by FAB-rlass spectrometer, and the amino acid composition analysis showed that the purified siderophore consisted of glycine/threonine/serine/glutamic acid/alanine/lysine with the molar ratio of 3:2:1:1:1:1, DL-Threo-${\beta}$-hydroxyaspartic acid and $N^{\delta}$-hydroxyornithine, two of the essential constituents of pyoverdin, were also found. The purified siderophore pyoverdin showed strong in vitro and in vivo antagonistic activities against phytophthora blight-causing P. capsici. Especially in an in vivo pot test, the siderophore protected red-pepper Capsicum annum L. very well from the attack of P. capsici. These results indicated that the purified siderophore of P. fluorescens 2112 played a critical role in the biocontrol of the red-pepper blight disease, equivalent to treatment by P.fluorescens 2112 cells.