Rhizosphere Bacterial Isolates Research Articles

The Impact of Rhizospheric and Endophytic Bacteria on the Germination of Carajasia cangae: A Threatened Rubiaceae of the Amazon Cangas.

Carajasia cangae (Rubiaceae) is a narrow endemic species from the canga ecosystems of the Carajás National Forest that is facing extinction due to a limited range and habitat disturbance from hydroclimatological changes and mining activities. This study examines the influence of rhizospheric and endophytic bacteria on C. cangae seed germination to support conservation efforts. Soil samples, both rhizospheric and non-rhizospheric, as well as plant root tissues, were collected. Bacteria from these samples were subsequently isolated, cultured, and identified. DNA sequencing revealed the presence of 16 isolates (9 rhizospheric and 7 endophytic), representing 19 genera and 6 phyla: Proteobacteria, Actinobacteria, Acidobacteria, Firmicutes, Bacteroidetes, and Chloroflexi. The endophytic isolates of Bacillus and the rhizospheric isolates of Planococcus and Lysinibacillus reduced the median germination time and initiation time, while the rhizospheric isolates Serratia and Comamonas increased the germination time and decreased the germination percentage in comparison to the control sample. These findings emphasize the crucial role of endophytic bacteria in the germination of C. cangae and highlight isolates that could have beneficial effects in the following stages of plant growth. Understanding the impact of endophytic and rhizospheric bacterial isolates on seed germination can enhance conservation efforts by shortening the germination period of this species and thereby improving seedling production. Additionally, this knowledge will pave the way for future research on the role of bacteria in the establishment of C. cangae.

Assessment of Antifungal Potential of Rhizospheric Bacterial Isolates of Daucus carota against Rhizoctonia solani

Rhizoctonia solani is an important plant pathogen which is responsible for causing a number of plant diseases in a variety of cropping plants. The current studies were carried out to explore antifungal potential of bacteria isolated from rhizospheric region of Daucus carota against Rhizoctonia. Of the total 21 bacterial isolates isolated, only 3 isolates namely CVO-3, CVO-4 and CRY-O-2 were shown antifungal potential against Rhizoctonia. Besides having antifungal potential these isolates also have some plant growth promoting attributes that will be an extra benefit of using these isolates as a biofungicides against R. solani. Thus, these isolates could be used as biofungicides against Rhizoctonia to prevent a variety of plant diseases like sheath blight in Oryza sativa, stem canker and black scurf in Solanum tuberosum and seedling diseases in Brassica napus. The isolates CVO-3, CVO-4 and CRY-O-2 were also characterized biochemical level by using methods based on Determinative Bacteriology given in Bergey’s manual and at molecular level using 16S rRNA sequencing and sequences of 16S rDNA segment were submitted to NCBI in GenBank database with the accession numbers OR775574 (Lysinibacillus boronitolerans ss3cvo3), OR775575 (Lysinibacillus boronitolerans ss4cvo4) and OR708523 (Shouchella rhizosphaerae ss1cryo2). The present investigation is an approach towards the use of these bacterial isolates from carrot rhizosphere to control the activities in the rhizosphere of other cropping plants.

Production, characterization and application of lipases from endophytic and rhizospheric bacterial isolates

Production, characterization and application of lipases from endophytic and rhizospheric bacterial isolates

Biological control of grey mould in strawberry fruits by soil Rhizosphere bacterial isolates

The goal of this study was to find effective bacterial isolates possessing antagonistic effects against Botrytis cinerea in strawberry in field conditions and to evaluate the antifungal properties of the extracellular metabolites produced by these isolates. Four bacterial isolates with considerable antifungal activity against B. cinerea were isolated from strawberries collected from local markets in Giza, Egypt. The molecular identification of bacterial isolates indicated that two of the isolates belong to the Bacillus subtilis, while the other two isolates belong to Pseudomonas stutzeri. The supernatants of the isolates were extracted and subjected to GC/MS analysis, which revealed that the supernatants of the isolates contained different types of fatty acids with expected antifungal activity. The most potent B. subtilis strain was further applied as a foliar spray over heavily infected strawberry fields, which led to significant reduction of B. cinerea. Therefore, this strain should be investigated further.

Antifungal potential of rhizospheric bacterial isolates of Daucus carota against brown spot fungus Cochliobolus miyabeanus

Cochliobolus miyabeanus is an important plant pathogen which causes a very common and widespread brown spot disease in rice, that may result in a severe reduction in the crop yield. The current studies were carried out to search out the antifungal potential of the bacterial isolates from the rhizospheric region of Daucus carota against brown spot fungus, C. miyabeanus. Isolation of rhizospheric bacterial isolates was done from carrot grown field of district Jaunpur in month of January, 2023. Experiment work has been done in Department of Biotechnology, Veer Bahadur Singh Purvanchal University, Jaunpur in 2023 from the month January to November. All bacterial isolates were tested for antifungal activity against brown spot fungi. Isolates were screened for their antifungal activities against brown spot fungus for further studying plant growth promoting, biochemical and morphological attributes. Isolates, CVO-7 and NBRI-O-2 showed efficient antifungal activity against test organism and also showed some plant growth promoting attributes that can further reduce the virulence of C. miyabeanus by enhancing availability of essential and trace elements for the plant. Both the isolates were characterized at a molecular level by using 16S rRNA gene sequencing and sequences of 16S rDNA segment were submitted to the NCBI GenBank database with the accession numbers OR775577 (Bacillus subtilis ss5cvo7) and OR775572 (Bacillus proteolyticus ss2nbrio2).

Plant-Disease-Suppressive and Growth-Promoting Activities of Endophytic and Rhizobacterial Isolates Associated with Citrullus colocynthis.

This study was conducted to investigate the antagonistic potential of endophytic and rhizospheric bacterial isolates obtained from Citrullus colocynthis in suppressing Fusarium solani and Pythium aphanidermatum and promoting the growth of cucumber. Molecular identification of bacterial strains associated with C. colocynthis confirmed that these strains belong to the Achromobacter, Pantoea, Pseudomonas, Rhizobium, Sphingobacterium, Bacillus, Sinorhizobium, Staphylococcus, Cupriavidus, and Exiguobacterium genera. A dual culture assay showed that nine of the bacterial strains exhibited antifungal activity, four of which were effective against both pathogens. Strains B27 (Pantoea dispersa) and B28 (Exiguobacterium indicum) caused the highest percentage of inhibition towards F. solani (48.5% and 48.1%, respectively). P. aphanidermatum growth was impeded by the B21 (Bacillus cereus, 44.7%) and B28 (Exiguobacterium indicum, 51.1%) strains. Scanning electron microscopy showed that the strains caused abnormality in phytopathogens' mycelia. All of the selected bacterial strains showed good IAA production (>500 ppm). A paper towel experiment demonstrated that these strains improved the seed germination, root/shoot growth, and vigor index of cucumber seedlings. Our findings suggest that the bacterial strains from C. colocynthis are suppressive to F. solani and P. aphanidermatum and can promote cucumber growth. This appears to be the first study to report the efficacy of these bacterial strains from C. colocynthis against F. solani and P. aphanidermatum.

Potential of local Bacillus spp. isolates as wilt disease biocontrol agents for Fusarium oxysporum f. sp. cepae on Allium x wakegi

Abstract. Asrul. 2023. Potential of local Bacillus spp. isolates as wilt disease biocontrol agents for Fusarium oxysporum f. sp. cepae on Allium x wakegi. Biodiversitas 24: 4989-4997. Implementation of biological agents for eradication and inhibition of plant pathogens is often ineffective due to its protracted consequences. The objective of this research was to examine the potential of local isolates of Bacillus spp. as a biocontrol agent in suppressing Fusarium wilt disease (Fusarium oxysporum f. sp. cepae) on wakegi onions (Allium × wakegi Araki). The research was conducted in a completely randomized design (CRD) with the treatment of rhizospheric bacterial isolates. The treatments included control (without isolate application) and seven bacterial isolates, namely KP17, KP5, DB9, DB12, DB18, DG4 and DG11. Each treatment was repeated five times and each replication consisted of 10 wakegi onion plants. The results showed that a total of 46 isolates were isolated from the rhizosphere of wakegi onion and seven isolates among them were selected as biocontrol agents. These isolates had similarities with Bacillus spp. in accordance with the colony morphology, physiology and biochemical characteristics. Among the isolates found, DB12 emerged as the isolate that had the potential to be developed as a biocontrol agent.

Hemolysis and hypersensitive tests ease culture collection management of antagonistic bacteria

A biosafety assessment is a crucial first step in the management of microbial culture collection to screen and determine unexpected potential plant and human pathogenic bacteria. It is common to collect and store as many fresh culture collections from natural resources before being further evaluated for antagonist bacteria. As a result, a bulk of isolates must be preserved which required more effort and budget. Safety evaluations based on the hemolysis and hypersensitive reactions offer simple tests to ease culture collection management of antagonist bacteria. The study aimed to evaluate the safety of bacterial culture collection for their hemolysis and hypersensitive reactions. Ninety-five isolates of rhizosphere and endophytic bacterial isolates from the culture collections of the Department of Plant Protection-IPB University, Indonesian Industrial and Beverages Crops Research Institute, and Indonesian Spice and Medicinal Crops Research Institute, were evaluated their safety using the hemolysis and hypersensitive tests. The hemolysis test was conducted using blood agar media, from which isolates with a negative (?) reaction were then tested for the hypersensitivity reaction on tobacco leaves. Bacterial isolates passed from both hemolysis and hypersensitivity tests were then preserved by the lyophilization method for long-term storage of culture collection. Based on the hemolysis test, 68 out of 95 bacterial isolates (71.57%) were found to be positive (? or ?) reactions. The hypersensitive test showed that 22 of 27 negative hemolysis isolates did not trigger hypersensitivity reactions in tobacco leaves, therefore, they were preserved by lyophilization. The study indicated that a high number of bacterial isolates in the present collection, 68 positive hemolysis, and 5 hypersensitive, need to be re-evaluated due to their safety concerns. The present study highlights the importance of biosafety tests performed in an early stage before the to permanent collection of antagonist isolates.

Bacillus velezensis BER1 enriched Flavobacterium daejeonense-like bacterium in the rhizosphere of tomato against bacterial wilt.

Beneficial microorganisms can protect crop from phytopathogens, and modify rhizosphere microbiome. However, it is not well-understood whether or how do rhizosphere microorganisms which respond to bioagents contribute to disease suppression. Bacillus velezensis BER1 and tomato bacterial wilt caused by Ralstonia solanacearum were selected as models to disentangle the interactions and mechanisms in the rhizosphere. Bacillus velezensis BER1 greatly suppressed tomato bacterial wilt by over 49.0%, reduced R. solanacearum colonization in the rhizosphere by 36.3%, and significantly enriched two Flavobacterium ASVs (1357 and 2401). A novel colony loop-mediated isothermal amplification (LAMP) assay system was developed to screen out Flavobacterium from tomato rhizosphere bacterial isolates. In vitro tests revealed that cocultivating BER1 with Flavobacterium C45 increased biofilm formation by 18.6%. Climate chamber experiment further revealed that Flavobacterium C45 improved the control efficiency of BER1 on tomato bacterial wilt by 46.0%, decreased the colonization of R. solanacearum in the rhizosphere by 43.1% and elevated the transcription of plant defense gene PR1α in tomato by 45.4%. In summary, Flavobacterium C45 boosted the ability of B. velezensis BER1 to prevent bacterial wilt and the colonization of R. solanacearum, highlighting the importance of helper bacteria on elevating the efficiency of biological control.

Field Evaluation of the Efficacy of Fungicides and Rhizosphere Bacterial Antagonists against Rice Stem Rot Disease

Rice stem rot disease in paddy cultivation leads to reduction of yield. Management of this disease is difficult as it is soil borne. In the present study, field trials were conducted during Rabi 2016-17 and early Kharif 2017-18 to assess the effectiveness of twelve fungicides and four rhizosphere bacterial antagonistic isolates (RRB-1 to RRB-4) against rice stem rot disease. Disease incidence was recorded from the date of initial incidence of the disease i.e., once in 15 days from maximum tillering to panicle emergence. Pooled analysis reveals that Hexaconazole recorded lowest per cent disease index (32.22) with highest grain yield and straw yield of 7.43 t/ha and 7.22 t/ha respectively, followed by Difenoconazole with grain yield and straw yield of 7.29 t/ha and 6.88 t/ha respectively. On the other hand, bacterial antagonists using root dipping and foliar spray with RRB-4 showed less PDI of 32.92 with grain yield of 6.97 t/ha and straw yield of 6.61 t/ha. With this study, hexaconazole (0.2%) and bacterial antagonists RRB-4 using root dipping and foliar spray (105 to 106 CFU/ml) can be effectively managed the rice stem rot.

Identification of Quorum Quenching N-Acyl Homoserine Lactonases from Priestia aryabhattai J1D and Bacillus cereus G Isolated from the Rhizosphere

Several pathogenic bacteria communicate using N-acyl homoserine lactone (AHL) as a quorum sensing (QS) molecule. The process of interfering with the QS system is known as quorum quenching (QQ), it is an effective tool to control QS-dependent virulence in pathogens. In the present study, rhizosphere bacterial isolates were screened for their ability to produce AHL lactonase enzyme as QQ molecules, which hydrolyses AHL signalling molecules and consequently blocks the QS system. Potent N-hexanoyl-l-homoserine lactone (C6HSL) hydrolytic QQ activity was detected in rhizosphere isolates namely Bacillus cereus G and Priestia aryabhattai J1D. The cell-free supernatant of the bacterial isolates indicated a reduction in biofilm formation in the human pathogens Vibrio cholerae, Pseudomonas aeruginosa, and Staphylococcus aureus without inhibiting cells, signifying their biocontrol property. Furthermore, liquid chromatography high resolution mass spectrometry analysis confirmed C6HSL hydrolytic activity by AHL lactonase produced by these rhizosphere isolates. Also, the aiiA homologous gene from the bacterial isolates showed similarity with the aiiA lactonase gene from Bacillus species, which was further confirmed by homology modelling. In silico structure analysis by comparing with the structure of Bacillus revealed the similarity in the active site, indicating the same degradation pattern. Based on available reported data, the present study indicates the first report of the presence of the aiiA lactonase gene in P. aryabhattai.

ASSESSMENT OF QUORUM QUENCHING ACTIVITY OF SERRATIA SPP. ISOLATED FROM PLANT RHIZOSPHERE AGAINST QUORUM SENSING CONTROLLED BIOFILM-FORMING PATHOGENS

Quorum quenching is the process of blocking quorum sensing activity that can be used as an effective way to control quorum sensing dependent virulence in pathogens. Quorum quenching mechanisms prevent the development of antibiotic resistance in biofilm-forming microorganisms. Rhizospheric bacteria shows great diversity along with complex intra species interactions. Within this diversified environment many bacterial species with quorum sensing and quorum quenching ability are found in close vicinity. In this study rhizospheric soil of different plants was used to screen potential quorum quenchers. The rhizospheric bacterial isolates were tested for their ability to degrade/inactivate N-hexanoyl-l-homoserine lactone (C6HSL) molecules. Pigment inhibition bioassays were performed using Chromobacterium violaceum CV026 and C. violaceum 2656 to screen bacterial isolates possessing quorum quenching activity. The biofilm formation inhibition by six screened isolates was studied against different human pathogens such as Vibrio parahaemolyticus MTCC451, V. cholerae MTCC3906 and Pseudomonas aeruginosa PA01. Results revealed that biofilms were efficiently inhibited. Significant biofilm inhibition was revealed by two isolates and identified as S. marcescens subsp. sakuensis KRED, and S. nematodiphila using 16S rRNA gene sequencing technique. The partial purification of C6HSL inactivating quorum quenching molecule resulted in maximum pigment inhibition of C. violaceum 2656 at 80% saturation of ammonium sulphate. These findings revealed that S. marcescens subsp. sakuensis KRED and S. nematodiphila are found to be potential candidates to control biofilms in bacterial human pathogens.

Characterization of Siccibacter sp. Strain C2 a Novel Rhizobacterium that Enhances Tolerance of Barley to Salt Stress.

Plant growth promoting rhizobacteria (PGPR) arouse an increasing interest as an eco-friendly solution for improving crop tolerance to environmental stresses. In this study, we report the characterization of a novel halotolerant PGPR strain (named C2) identified in a screen of rhizospheric bacterial isolates from southeast of Tunisia. Phylogenetic analysis showed that strain C2 is most likely affiliated to the genus Siccibacter with Siccibacter turicensis as the closest species (98.19%). This strain was able to perform phosphate solubilization and production of indole acetic acid (IAA), siderophores, hydrogen cyanide (HCN), as well as different hydrolytic enzymes (proteases, amylases, cellulases, and lipases). The potential of strain C2 in enhancing salt stress tolerance of Hordeum vulgare was also investigated. Our greenhouse inoculation assays showed that strain C2 promotes barley growth in the presence of 400mM NaCl by increasing biomass, root length, and chlorophyll contents. It has a positive effect on the photosynthetic efficiency, concomitantly with lower intercellular CO2 contents, compared to non-inoculated plants. Moreover, barley inoculation with strain C2 under salt stress, resulted in higher accumulation of proline and soluble sugars and alleviate the oxidative stress by decreasing hydrogen peroxide and malondialdehyde contents. Remarkably, this positive effect corroborates with a significant activation in the expression of a subset of barley stress responsive genes, including HVA1, HvDREB1, HvWRKY38 and HvP5CS. In summary, Siccibacter sp. strain C2 is able to enhance barley salt stress tolerance and should be leveraged in developing sustainable practices for cereal crop production.

Acinetobacter calcoaceticus SJ19 and Bacillus safensis SJ4, two Algerian rhizobacteria protecting tomato plants against Botrytis cinerea and promoting their growth

BackgroundBotrytis cinerea, the causal agent of grey mould, is a polyphagous fungus that infects a wide range of plants, including tomato. In many countries, including Algeria, the management of grey mould is a challenging problem, even with chemical control. This necessitates the search for other strategies. The objective of this study was to evaluate the biocontrol potential of two rhizospheric bacterial isolates for the protection of tomato against B. cinerea.ResultsOn tomato plants, the two bacterial isolates consistently provided high levels of protection (on average 72.1% for SJ19 and 52.3% for SJ4). Their applications as a 1:1 mixture reinforced their effect (87.8% protection), indicating their compatibility and a potential use as a consortium. In vitro, the isolates significantly inhibited the mycelial growth of B. cinerea strains, both through direct confrontation in dual-culture assays (12–69% inhibition) and through the production of volatile compounds (36–46% inhibition). The two isolates, applied as seed treatment and as drench on seedlings, also showed strong growth-promoting effects on tomatoes. They substantially increased the length and fresh weight of shoots and roots, as well as stem diameter, leaf number and chlorophyll content, compared to untreated plants.ConclusionThe two bacteria tested in this study showed a high potential for use as biostimulants and as biofungicides against tomato grey mould.

Antagonistic activity of resident biological agents against wilt and root rot pathogens of pea in different culture media

Antagonistic potential of rhizospheric fungal and bacterial isolates evaluated against wilt and root-rot pathogens of pea exhibited significant effect on radial growth inhibition of pathogens in comparison to control. Two isolates of Trichoderma spp., one isolate of Aspergillus niger, one isolate of Penecillium oxalicum and three isolates of Pseudomonas were isolated from rhizosphere of pea and were evaluated for their antagonistic potential against three soil borne plant pathogens viz., Fusarium oxysporum f. sp, pisi, Rhizoctonia solani and Pythium ultimum using dual culture technique in different culture media (potato carrot agar, czapek dox agar, rose bengal chloramphenicol and czapek malt agar). Antagonistic potential of fungal and bacterial isolates were found to be significantly influenced in different culture media. All fungal and bacterial isolates preferred potato carrot agar and czapek dox agar media and resulted in maximum reduction in growth of test pathogen on the culture media.

SYNERGISM BETWEEN RHIZOSPHERE BACTERIA ISOLATES FROM Scleria sp., Clidemia sp., AND Panicum sp. TO INCREASE THE EFFECTIVENESS OF MIXED CULTURES IN HYDROCARBON BIODEGRADATION

The purpose of this research is to obtain hydrocarbon degrading bacteria that work synergistically in a consortium. Consortium microorganisms is mixture of microbial populations in the form of communities that have mutualistic relationships and doesn’t inhibition the growth of other microbes. In this study, isolates were obtained from the rhizosphere of soil contaminated with petroleum. The isolates obtained were tested for synergism to determine the relationship between bacterial isolates. Synergism testing was carried out using the spread plate method on agar media. The results of this study showed that isolate number one showed antagonistic properties to other bacterial isolates by forming a clear zone around the disc paper. A total of eight bacterial isolates showed the greatest percentage of synergism, namely ≥ 80% so that the eight rhizosphere bacterial isolates could be used as materials for mixed culture.

Isolation and Biochemical Characterization of Indole-3-Acetic Acid (IAA) Produced in Pseudomonas Sp. Isolated from Rhizospheric Soil

A phytohormone is a molecule that controls the development of plants. Auxin and cytokines, which may be acquired as synthetic compounds or produced by microorganisms, which promote plant growth, are employed to enhance crop yield. Indole-3-Acetic Acid (IAA) is a key phytohormone that controls a number of physiological processes in plants. Indole-3-acetic acid (IAA), the most prevalent endogenous auxin, is involved in stem elongation and root formation. Auxin levels are usually higher in the rhizosphere. The possibility of rhizosphere bacteria to encourage direct plant development has been recognised as a crucial component of auxin (IAA) production. They promote the growth of lateral roots, which increases the surface area available for nutrition absorption and enhances nutrient and water absorption from the soil. The objective of this research is to isolate, characterise, and identify bacteria that produce indole acetic acid in rhizospheric soil. Bacterial colonies were isolated using the serial dillution technique on nutrient agar medium from rhizospheric soil samples of a rice crop. Five rhizospheric bacterial isolates (RIPB-1 to RIPB-30) were identified as effective Indole acetic acid makers after qualitative screening. The quantity of Indole acetic acid produced by five bacterial strains was tested for up to 120 hours. The amount of Indole acetic acid they could generate ranged from 1 to 11.2 g/ml. The bacterial strain RIPB-20 (11.2 g/ml) generated the highest Indole acetic acid after 72 hours of incubation, followed by RIPB-14. Based on morphological, physiological, and biochemical features, the bacterial isolate RIPB-20 was tentatively identified as Bacillus sp. Finally, the finding shows that the bacteria, which have capacity to produce Indole acetic acid, are good biofertilizer inoculants for growth of plant.

Biological control in the germination of seeds from two species native of the Cerrado region.

Microorganisms have been efficiently used for the biological control of phytopathogens through the production of antimicrobial substances. However, the objectives of this work were: to study the germination of Butia purpurascens Glassman and Butia archeri Glassman seeds in different substrates, to select and identify the endophytic and rhizospheric bacterial isolates of B. purpurascens and B. archeri, and to perform antibiosis tests based on the isolated microorganisms of these tree species. No difference was found between the cultivation substrates for the percentages of germination, hard seeds, and fungal contamination in the B. purpurascens seeds. The Bacillus subtilis isolated showed the best capacity for suppressing the growth of the two deteriorative fungi tested in B. purpurascens seeds. No difference was found for inhibition of the growth of Aspergillus niger fungus (deteriorative fungus of B. archeri seeds) between the microorganisms with Bacillus sp. and Brevibacillus brevis compared to the control. In the microbiolization of B. purpurascens and B. archeri seeds performed with microbiological solutions produced from the endophytic and rhizospheric strains of Bacillus sp., no differences were observed in the percentages of germination and contamination by fungi. For B. archeri seeds, there was contamination by fungi and bacteria after one day of cultivation, primarily in the regions with lesions caused by the extraction and scarification process.

Assessment of antibiosis potential of Bacillus sp. against the soil-borne fungal pathogen Sclerotium rolfsii Sacc. (Athelia rolfsii (Curzi) Tu & Kimbrough)

BackgroundThis study aimed to investigate the rhizosphere bacterial isolates’ antagonistic property against the soil-borne fungal phytopathogen, Sclerotium rolfsii Sacc. (Athelia rolfsii (Curzi) Tu & Kimbrough). The chemical control of the disease caused by S. rolfsii is economically and environmentally unsustainable, and therefore, a bio-control agent in the form of rhizospheric bacteria is gaining importance.Main bodyFive rhizospheric Bacillus species viz. B. subtilis subsp. Subtilis str.168 (accession no. MH283878), B. siamensis strain PDA 10 (accession no. MH283879), B. amyloliquefaciens strain 1034 (accession no. MH283880), B. velezensis strain FZB42165 (accession no. MH283881), and B. atrophaeus strain NBRC 15539 (accession no. MH283882) were assessed for their antagonistic potential against S. rolfsii based on 3 different screening methods. Among these, 100% fungal growth inhibition by all 5 Bacillus spp. was observed in the novel ring method, whereas in the dual culture method, the maximum growth inhibition was (58%) exhibited by the strain NBRC 15539 of B. atrophaeus. The antagonistic activity showed by the modified dual culture method was also relatively high, and the highest activity (93.7%) was shown by the strain NBRC 15539 of B. atrophaeus. Besides, the Bacillus sp. was also evaluated for their plant growth-promoting attributes and other properties such as the production of siderophore, HCN, amylase, protease, lipase, and ammonia, including their assessment for chitinase and cellulase activity.ConclusionThe study provided empirical evidence of Bacillus sp. antagonistic potential against S. rolfsii and should be of contributive value in developing a biocontrol agent for this highly important crop fungal pathogen.

Selection of Rhizosphere Bacterial Isolates and Development of Antagonistic Bacterial-Based Formulation to Control Fusarium Wilt on Shallot

<p>Wilt disease caused by Fusarium spp. is a major disease in shallot-producing areas particularly in the North Coast of West Java. The research was aimed to select rhizosphere bacteria and develop an antagonistic bacterial-based formulation for its effectiveness to suppress wilt disease caused by Fusarium spp. on shallot plant under greenhouse and field trials. The field trials were carried out using randomized complete block design with four replications at the shallot farmer condition in Subang and Indramayu during the 2019 planting season. Antagonistic test of bacterial isolates from the rhizosphere showed that most of the bacterial isolates can be used as a biocontrol to Fusarium spp. pathogen. The result revealed that bacterial suspension formulation (E-76 + DBS-2 isolates) in combination with phytohormone (1:1 [v/v]) at Subang and Indramayu tended to suppress Fusarium wilt disease intensity with the disease inhibition ranging from 73.54–93.39% and 66.3–95.65%, respectively. The spraying application of formulation 2.5 ml/l was obtained as the best formula to suppress the disease. The growth and production of shallot were also affected by the application of antagonistic-bacterial formula.</p>