• The Plant Pathology Journal
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• 제37권2호
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• pp.173-181
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• 2021

The genus Streptomyces demonstrates enormous promise in promoting plant growth and protecting plants against various pathogens. Single and consortium treatments of two selected Streptomyces strains (Streptomyces shenzhenensis TKSC3 and Streptomyces sp. SS8) were evaluated for their growth-promoting potential on rice, and biocontrol efficiency through induced systemic resistance (ISR) mediation against Xanthomonas oryzae pv. oryzicola (Xoc), the causal agent of rice bacterial leaf streak (BLS) disease. Seed bacterization by Streptomyces strains improved seed germination and vigor, relative to the untreated seed. Under greenhouse conditions, seed bacterization with consortium treatment TKSC3 + SS8 increased seed germination, root length, and dry weight by 20%, 23%, and 33%, respectively. Single and consortium Streptomyces treatments also successfully suppressed Xoc infection. The result was consistent with defense-related enzyme quantification wherein single and consortium Streptomyces treatments increased peroxidase (POX), polyphenol oxidase, phenylalanine ammonia-lyase, and β,1-3 glucanase (GLU) accumulation compared to untreated plant. Within all Streptomyces treatments, consortium treatment TKSC3 + SS8 showed the highest disease suppression efficiency (81.02%) and the lowest area under the disease progress curve value (95.79), making it the best to control BLS disease. Consortium treatment TKSC3 + SS8 induced the highest POX and GLU enzyme activities at 114.32 µmol/min/mg protein and 260.32 abs/min/mg protein, respectively, with both enzymes responsible for plant cell wall reinforcement and resistant interaction. Our results revealed that in addition to promoting plant growth, these Streptomyces strains also mediated ISR in rice plants, thereby, ensuring protection from BLS disease.

• Journal of Microbiology and Biotechnology
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• 제28권6호
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• pp.968-975
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• 2018

In the course of screening for microbes with nematicidal activity, we found that Enterobacter asburiae HK169 displayed promising nematicidal activity against the root-knot nematode Meloidogyne incognita, along with plant growth-promoting properties. Soil drenching of a culture of HK169 reduced gall formation by 66% while also increasing root and shoot weights by 251% and 160%, respectively, compared with an untreated control. The cell-free culture filtrate of the HK169 culture killed all juveniles of M. incognita within 48 h. In addition, the nematicidal activity of the culture filtrate was dramatically reduced by a protease inhibitor, suggesting that proteolytic enzymes contribute to the nematicidal activity of HK169. In order to obtain genomic information about the HK169 isolate related to its nematicidal and plant growth-promoting activities, we sequenced and analyzed the whole genome of the HK169 isolate, and the resulting information provided evidence that the HK169 isolate has nematicidal and plant growth-promoting activities. Taken together, these observations enable the future application of E. asburiae HK169 as a biocontrol agent for nematode control and promote our understanding of the beneficial interactions between E. asburiae HK169 and plants.

• 한국균학회지
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• 제49권4호
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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.

• The Plant Pathology Journal
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• 제29권2호
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• pp.174-181
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• 2013

The plant growth-promoting rhizobacterium Ochrobactrum lupini KUDC1013 elicited induced systemic resistance (ISR) in tobacco against soft rot disease caused by Pectobacterium carotovorum subsp. carotovorum. We investigated of its factors involved in ISR elicitation. To characterize the ISR determinants, KUDC1013 cell suspension, heat-treated cells, supernatant from a culture medium, crude bacterial lipopolysaccharide (LPS) and flagella were tested for their ISR activities. Both LPS and flagella from KUDC1013 were effective in ISR elicitation. Crude cell free supernatant elicited ISR and factors with the highest ISR activity were retained in the n-butanol fraction. Analysis of the ISR-active fraction revealed the metabolites, phenylacetic acid (PAA), 1-hexadecene and linoleic acid (LA), as elicitors of ISR. Treatment of tobacco with these compounds significantly decreased the soft rot disease symptoms. This is the first report on the ISR determinants by plant growth-promoting rhizobacteria (PGPR) KUDC1013 and identifying PAA, 1-hexadecene and LA as ISR-related compounds. This study shows that KUDC1013 has a great potential as biological control agent because of its multiple factors involved in induction of systemic resistance against phytopathogens.

• 생명과학회지
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• 제31권7호
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• pp.641-653
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• 2021

본 연구에서는 근권토양으로부터 18종의 세균을 순수분리하고, 이들의 식물 병원성 진균 생육억제 활성, 식물생장촉진 활성 및 미네랄 가용화능을 평가하였다. Bacillus 속과 Pseudomonas 속 분리균주의 항진균 활성을 통해 생물학적 방제제로서의 가능성을 확인할 수 있었으며, 이는 식물 병원성 진균의 세포벽에 작용하는 여러 가수분해효소 활성과 siderophore 생성능 등에 기인된 것으로 판단된다. 또한 대부분의 분리균주가 aminocyclopropane-1-carboxylate deaminase 생성능, indole-3-acetic acid 생성능 및 질소 고정능을 갖고 있는 것으로 나타났으며, 이러한 특성은 식물이 흔히 노출될 수 있는 환경 스트레스 조건 하에서 스트레스 에틸렌의 농도를 감소시킴으로써 뿌리 발달 및 성장, 그리고 작물의 생산성에 긍정적인 영향을 줄 것으로 판단된다. 그리고 분리균주의 인산, 규소, 탄산칼슘, 아연 가용화능 등을 확인한 결과, 일부 분리균주들의 미네랄 가용화능을 확인하였으며, 이들 분리균주를 식물 생장 시에 접종한다면 식물 생장에 필요한 영양분을 식물이 흡수할 수 있는 이용가능한 형태로 변환시켜 식물의 생장에 도움을 줄 수 있을 것으로 기대된다. 이러한 항진균 활성, 식물생장촉진 활성 및 미네랄 가용화능의 결과를 통해 분리균주 18종의 biocontrol agent로서의 이용가능성을 제시하고자 한다.

• The Plant Pathology Journal
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• 제35권2호
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• pp.137-148
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• 2019

In search of an effective biological control agent against the tomato pathogen Fusarium oxysporum f. sp. lycopersici, rhizospheric soil samples were collected from eight agro-ecological zones of Bangladesh. Among the bacteria isolated from soil, 24 isolates were randomly selected and evaluated for their antagonistic activity against F. oxysporum f. sp. lycopersici. The two promising antagonistic isolates were identified as Brevundimonas olei and Bacillus methylotrophicus based on morphological, biochemical and molecular characteristics. These two isolates were evaluated for their biocontrol activity and growth promotion of two tomato cultivars (cv. Pusa Rubi and Ratan) for two consecutive years. Treatment of Pusa Rubi and Ratan seeds with B. olei prior to inoculation of pathogen caused 44.99% and 41.91% disease inhibition respectively compared to the untreated but pathogen-inoculated control plants. However, treatment of Pusa Rubi and Ratan seeds with B. methylotrophicus caused 24.99% and 39.20% disease inhibition respectively. Furthermore, both the isolates enhanced the growth of tomato plants. The study revealed that these indigenous bacterial isolates can be used as an effective biocontrol agent against Fusarium wilt of tomato.

• The Plant Pathology Journal
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• 제34권3호
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• pp.218-235
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• 2018

Plant growth promoting rhizobacteria and endophytic bacteria were isolated from different varieties of turmeric (Curcuma longa L.) from South India. Totally 50 strains representing, 30 PGPR and 20 endophytic bacteria were identified based on biochemical assays and 16S rDNA sequence analysis. The isolates were screened for antagonistic activity against Pythium aphanidermatum (Edson) Fitzp., and Rhizoctonia solani Kuhn., causing rhizome rot and leaf blight diseases in turmeric, by dual culture and liquid culture assays. Results revealed that only five isolates of PGPR and four endophytic bacteria showed more than 70% suppression of test pathogens in both assays. The SEM studies of interaction zone showed significant ultrastructural changes of the hyphae like shriveling, breakage and desication of the pathogens by PGPR B. cereus (RBacDOB-S24) and endophyte P. aeruginosa (BacDOB-E19). Selected isolates showed multiple Plant growth promoting traits. The rhizome bacterization followed by soil application of B. cereus (RBacDOB-S24) showed lowest Percent Disease Incidence (PDI) of rhizome rot and leaf blight, 16.4% and 15.5% respectively. Similarly, P. aeruginosa (BacDOB-E19) recorded PDI of rhizome rot (17.5%) and leaf blight (17.7%). The treatment of these promising isolates exhibited significant increase in plant height and fresh rhizome yield/plant in comparison with untreated control under greenhouse condition. Thereby, these isolates can be exploited as a potential biocontrol agent for suppressing rhizome rot and leaf blight diseases in turmeric.

• The Plant Pathology Journal
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• 제38권5호
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• pp.490-502
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• 2022

Xanthomonas oryzae pv. oryzae (Xoo) causes bacterial leaf blight (BLB) disease in rice (Oryza sativa L.) and it is among the most destructive pathogen responsible for severe yield losses. Potential bacterial biocontrol agents (BCAs) with plant growth promotion (PGP) abilities can be applied to better manage the BLB disease and increase crop yield, compared to current conventional practices. Thus, this study aimed to isolate, screen, and identify potential BCAs with PGP abilities. Isolation of the BCAs was performed from internal plant tissues and rhizosphere soil of healthy and Xoo-infected rice. A total of 18 bacterial strains were successfully screened for in vitro antagonistic ability against Xoo, siderophore production and PGP potentials. Among the bacterial strains, 3 endophytes, Bacillus sp. strain USML8, Bacillus sp. strain USML9, and Bacillus sp. strain USMR1 which were isolated from diseased plants harbored the BCA traits and significantly reduced leaf blight severity of rice. Simultaneously, the endophytic BCAs also possessed plant growth promoting traits and were able to enhance rice growth. Application of the selected endophytes (BCAs-PGP) at the early growth stage of rice exhibited potential in suppressing BLB disease and promoting rice growth.

• 식물병연구
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• 제12권1호
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• pp.46-50
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• 2006

비경작 산림 토양으로부터 고추역병 억제와 초기생육 촉진 효과를 보이는 방선균을 분리하였다. 분리된 Streptomyces griseofuscus 200401은 역병균 뿐만 아니라 탄저병에 대하여 항균활성을 보였다. 분리 미생물 배양액과 그 제제의 생육초기단계 처리로 식물체의 엽수, 생물 중 및 건물 중 등이 대조구에 비해 증가하였다. 공시균주 배양액 중 유기질소원의 분해에 의한 ammonium chloride의 농도는 배양 후 0.13 ${\mu}g/ml$로 나타났다. 분리균주의 온실에서 고추역병 발생억제 효과를 검정한 결과, 1주일 간격으로 3회 처리한 경우 최종방제가가 37.3%로 대조약제와 유사하게 나타났다.

• 한국환경농학회지
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• 제20권1호
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• pp.57-62
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• 2001

여러 작물 재배지 토양에서 각종 근권미생물을 분리하여 이들 분리미생물 중 수박 만할병균인 Fusarium oxysporum f. sp. niveum(KCCM34741)에 길항하는 미생물인 YJ-19, YJ-45, YJ-3 등 12 균주를 분리하였다. 길항미생물들은 MS agar 배지 실험 및 미생물제제 첨가 상토 실험에서 모두 참박의 발아율을 향상시켰으며, 이들 중 분리주 YJ-3 균주는 참박의 발아율과 초기생육에 가장 큰 영향을 주는 미생물로 선별되었다. YJ-3 균주를 제제화하여 참박 재배 기간별로 식물체 생육실험을 행한 결과 대조구인 일반 상토 및 시판 미생물혼합 상토 보다 각각 46%와 13%정도 생육을 촉진하는 것으로 나타났다. 분리주 YJ-3 균주는 간균의 gram 양성균으로서 Bacillus sp.로 동정되었다. Bacillus sp. YJ-3은 수박 만할병균인 F. oxysporum f. sp. niveum에 대해 강한 억제효과를 나타내었고, 그외 수박 병원균인 Alternaria cucumerina, Botrytis cinerea, Colletotrichum orbiculare, Didymella bryoniae, Rhazoctonia solani 등에서도 우수한 길항력을 나타내어 본 Bacillus sp. YJ-3 균주는 수박 만할병균에 길항하는 동시에 참박의 생육을 촉진하는 미생물로 확인되었다.