• 한국식물병리학회지
• /
• 제11권4호
• /
• pp.304-311
• /
• 1995

To determine whether chitinolytic enzymes from Chromobacterium violaceum C-61 play an important role in the suppression of Rhizoctonia damping-off, Tn5 insertion mutants deficient in chitinolytic activity (Chi a- mutants) were selected and their chitinolytic and disease suppression were compared with those of the parental strain. Four Chi a- mutants selected from about 2,000 transconjugants did not inhibit mycelial growth of Rhizoctonia solani on nutrient agar-potato dextrose agar (BA-PDA) and their abilities to suppress Rhizoctonia damping-off were much lower than the parental strain. However, population density in the eggplant rhizosphere did not differ significantly between the parental strain and four Chi a- mutants. The crude enzyme of the parental strain inhibited growth of R. solani on NA-PDA and its chitinase activity was much higher than that of Chi a- mutants. But the N,N' -diacetylchitobiase activity between these isolates were not significantly different. The chitinase of Chi a- mutants was defective in 2 isoforms of 52- and 37-kDa among four isoforms of 54-, 52-, 50- and 37-kDa. A Tn5 element was inserted into one site of 10 kb EcoRI fragment of chromosomal DNA in three Chi- mutants, C61-C1, -C2, and -C3. In C61-C4 mutant, a Tn5 element was inserted into two sites of 10 kb and 4.4 kb EcoRI fragments. These results suggest that the chitinase of C. violaceum C-61 play an important role in the suppression of Rhizoctonia damping-off of cucumber and eggplant.

• Journal of Ginseng Research
• /
• 제29권4호
• /
• pp.185-191
• /
• 2005

In vitro and in vivo effectiveness of fungicides were evaluated for the control of damping off caused by Rhizoctonia solani on Panax ginseng. Fludioxonil(67 mg a. i./L), flutolanil(75 mg a. i./L), thifluzamide(35 mg a. i./L), and mepronil (750 mg a. i./L) were selected from 9 fungicides, which were based on inhibition of mycelial growth of R. solani (isolate Rh 9801) and duration of fungicidal effectiveness against the pathogen in vitro. Field trials were made twice in the year of 2003 and 2004. Experimental plots $(54m{\times}0.9m)$ of 4-year-old ginseng fields were artificially infested with 5kg and 14 kg in fresh weight of inoculum in 2003 and 2004, respectively. The fungicides were drenched at a volume of 8l in $3.6m{\times}0.9m$ with 3 replications. Fludioxonil, flutolanil, thifluzamide and mepronil reduced the incidence of damping off by $73\%,\;69\%,\;69\%\;and\;43\%$, respectively. In the 2004 trial, fludioxonil, flutolanil, and thifluzamide showed similar result as reducing the incidence by $85\%,\;84\%,\;and\;82\%$, respectively, in the plot where the inoculum was applied 2.8 times more than the 2003. The disease incidences in untreated control were $12\%$ in 2003 and $47\%$ in 2004.

• 한국식물병리학회지
• /
• 제14권6호
• /
• pp.606-611
• /
• 1998

An antagonistic bacterium, Pseudomonas flurorescens MC07 inhibited the mycelial growth of Rhizoctonia solani, Pythium ultimum, Fusarium oxysporum, and Phytophthora capsici in on potato dextrose agan (PDA) and other media. The strain MC07 conlonizes various plant roots and possesses antifungal activity. To determine the role of antifungal activity of the bacterium in disease suppression, a mutant Okm3-4 which lost its activity was isolated after screening 2,500 colonies generated by Omegon-Km insertions. The mutant Okm3-4 showed diminished growth inhibition of R. solani, P. ultimum, F. oxysporum, and Ph. capsici in vitro and had reduced suppressive effects on sesame damping.-off compared to the parental strain. In soils, accumulation of the pathogens by continuous cropping, 90% of sesame plants were killed by natural infection of damping-off whereas, only 29% of plants grown from seeds treated with MC07 were killed. On the other hand, 85% of plants died when sesame seeds were treated with the Okm3-4 cells. This indicated that antifungal activity of MC07 in vitro is directly responsible for the suppression of damping-off disease. Emergence rates of sesame seeds in pots containing diseased soil were 33%. However, MC07 treatments on seeds significantly improved emergence rates, which has similar effects of Benomyl treatment. The mutant Okm3-4 exhibited 53% of emergence rate. This indicated that antifungal activity of MC07 also affects the emergence rate of sesame seeds.

• 한국식물병리학회지
• /
• 제10권4호
• /
• pp.319-324
• /
• 1994

The monoxenic culture of the fungivorous nematode, Aphelenchus avenae, was applied for the control of soil-borne ginseng pathogens such as Fusarium solani and Rhizoctonia solani. Fungivorous nematode populations were measured in a field to examine relationships between the nematode populations and suppression of ginseng root diseases. Inoculation of A. avenae (5000 nematodes per petri-dish) reduced the colonization of the Fusarium mycelium on root discs of ginseng and carrot by 80.0% and 60.5%, respectively. A. avenae also significantly reduced the occurrence of damping-off of ginseng by R. solani pathogenic to ginseng, and no plant damage by the nematode was noted. In a 3-year-old ginseng field infested with Cylindrocarpon destructans, plant missing caused by root rot positively correlated to the density of potato rot nematode, Ditylenchus destructor, but it was reduced with the population of A. avenae, suggesting that A. avenae might inhibit the occurrence of ginseng root rot.

• 한국식물병리학회:학술대회논문집
• /
• 한국식물병리학회 2002년도 총회 및 추계학술발표회
• /
• pp.52.1-52
• /
• 2002

• 한국식물병리학회:학술대회논문집
• /
• 한국식물병리학회 1999년도 정기총회 및 춘계 학술발표회
• /
• pp.40.2-40
• /
• 1999

• 생명과학회지
• /
• 제12권4호
• /
• pp.416-422
• /
• 2002

B. ehimensis YJ-37은 생육촉진미생물이면서 모잘록병의 생물학적 방제균으로서 관찰되었다 길항균 B. ehimensis YJ-37의 무와 수박의 근권정착밀도는 인공용토에 존재하는 길항균의 평균밀도 $10^4$(cfu/g) 보다 주근과 측근에서 약 1.2~2배 이상의 증가하였다. 길항균 배양액으로 만든 토양미생물제제에 의한 무의 생육촉진은 토양미생물제제 무처리구에 비해 처리구에서 잎면적은 85% 자엽의 길이는 33% 뿌리의 길이는 23% 건조중량은 89% 촉진되었고, 수박의 경우도 무처리구에 비해 처리구에서 잎면적은 63% 자엽의 길이는 27% 뿌리의 길이는 25% 건조중량은 69% 촉진되었다. 토양미생물제제는 채소류 모잘록병균 R. solani AG-4와 P. ultimum 등의 생육을 억제하여 모잘록병을 유발시키지 못하게 하였으며, 생육촉진현상도 동시에 가져왔다.

• 한국식물병리학회지
• /
• 제11권3호
• /
• pp.252-257
• /
• 1995

Growth rates of the low temperature growing isolates, Pseudomonas fluorescens M45 and MC07, reached maximum stationary phase within 50 hrs at the low temperature, 4$^{\circ}C$. But an ordinary biocontrol agent P. putida Pf3 did not reach logarithmic growth phase until 80 hrs. The culture filtrates of M45 and MC07 significantly inhibited the mycelial growths of Pythium ultimum, Rhizoctonia solani and Phytophthora capsici. Detached cotyledons of cucumber grown on Murashige and Skoog agar medium were much enhanced in their growth, compared to those without the filtrates. Population densities of M45 and MC07 in the rhizosphere at 14$^{\circ}C$ were more stable than at 27$^{\circ}C$. When M45 and MC07 were treated into soil, the population density of MC07 continuously increased up to 9 days after treatment, and sustained the initial inoculum density up to 60 days. Cucumber damping-offs caused by P. ultimum and R. solani were significantly reduced by applying M45 as seed-inoculant and by soil treatment with MC07. The combined treatment of M45 and MC07 provided greater effect in reducing the disease incidence than that obtained by single treatments.

• Journal of Microbiology and Biotechnology
• /
• 제21권4호
• /
• pp.379-386
• /
• 2011

The objective of this work was to investigate the ability of the plant growth-promoting rhizobacterium Pseudomonas aureofaciens 63-28 to induce plant defense systems, including defense-related enzyme levels and expression of defense-related isoenzymes, and isoflavone production, leading to improved resistance to the phytopathogen Rhizoctonia solani AG-4 in soybean seedlings. Seven-day-old soybean seedlings were inoculated with P. aureofaciens 63-28, R. solani AG-4, or P. aureofaciens 63-28 plus R. solani AG-4 (P+R), or not inoculated (control). After 7 days of incubation, roots treated with R. solani AG-4 had obvious damping-off symptoms, but P+R-treated soybean plants had less disease development, indicating suppression of R. solani AG-4 in soybean seedlings. Superoxide dismutase (SOD) and catalase (CAT) activities of R. solani AG-4-treated roots increased by 24.6% and 54.0%, respectively, compared with control roots. Ascorbate peroxidase (APX) and phenylalanine ammonia lyase (PAL) activities of R. solani AG-4-treated roots were increased by 75.1% and 23.6%, respectively. Polyphenol oxidase (PPO) activity in soybean roots challenged with P. aureofaciens 63-28 and P+R increased by 25.0% and 11.6%, respectively. Mn-SOD (S1 band on gel) and Fe-SOD (S2) were strongly induced in P+R-treated roots, whereas one CAT (C1) and one APX (A3) were strongly induced in R. solani AG-4- treated roots. The total isoflavone concentration in P+Rtreated shoots was 27.2% greater than the control treatment. The isoflavone yield of R. solani AG-4-treated shoots was 60.9% less than the control.