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Antifungal activity of isolates PSB1 to PSB9 as determined by an in vitro bioassay (dual culture technique) on ISP5 medium. Average Inhibition index (I index) from three independent experiments are shown on a 0-100 scale. Bioassays were carried out against several phytopathogenic fungi: B. cinerea (Bc); P. herbarum (Ph); F. oxysporum (Fo); N. oryzae (No); Alternaria sp. (A); R. solani (Rs). Data shown were measured for each pathogen at different times when the Rc value of the negative control (pathogen growth in absence of antagonist PSB isolate) was 4.5 cm.
Source publication
On average less than 1% of the total phosphorous present in soils is available to plants, making phosphorous one of the most limiting macronutrients for crop productivity worldwide. The aim of this work was to isolate and select phosphate solubilizing bacteria (PSB) from the barley rhizosphere, which has other growth promoting traits and can increa...
Contexts in source publication
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... were carried out in several agar media, but ISP5 and ISP7 agar media were the only ones which supported the growth of all the fungal and bacterial strains used in the bioassay. The best results (shown in Figure 2) were obtained using ISP5 medium, although differences in the I index for the same pathogen were detected depending on the culture medium used (Supplementary Information Figure S1 shows the antifungal activity detected on ISP7 medium). Thus P. eucrina did not show any antifungal activity against any of the fungi tested on ISP5 medium (Figure 2), whereas in ISP7 medium a low antifungal activity was detected against B. cinerea and P. herbarum ( Figure S1). ...
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... best results (shown in Figure 2) were obtained using ISP5 medium, although differences in the I index for the same pathogen were detected depending on the culture medium used (Supplementary Information Figure S1 shows the antifungal activity detected on ISP7 medium). Thus P. eucrina did not show any antifungal activity against any of the fungi tested on ISP5 medium (Figure 2), whereas in ISP7 medium a low antifungal activity was detected against B. cinerea and P. herbarum ( Figure S1). Some of the isolates exhibited interesting antifungal properties against several of the pathogens. ...
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... N. oryzae (94.9%). In contrast, B. cereus PSB3 did not show any remarkable antifungal activity against either of the pathogens tested in ISP5 medium, whereas the rest of the PSB strains exhibited different rates of antifungal activity against the different pathogens tested (Figure 2). of the pathogens. Thus, B. megaterium PSB1 exhibited total growth inhibition of B. cinerea and Alternaria sp., and good antifungal activity against F. oxysporum (I index 96.5) ...
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... N. oryzae (94.9%). In contrast, B. cereus PSB3 did not show any remarkable antifungal activity against either of the pathogens tested in ISP5 medium, whereas the rest of the PSB strains exhibited different rates of antifungal activity against the different pathogens tested (Fig- ure 2). ...
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... upon visual inspection, plants revealed some clear differences in growth and development when the negative control was compared with the rest of the treatments. Indeed, mean height data for the negative control plants ( Figure 3A and Figure S2) was significantly lower than for the positive control and all the batches inoculated with the different PSBs. Some of the isolates (PSB1, PSB5, PSB6, PSB7 and PSB9) were even capable of inducing greater height growth than that observed for the positive control plants ( Figure 3A). ...
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... development when the negative control was compared with the rest of the treatments. Indeed, mean height data for the negative control plants ( Figure 3A and Figure S2) was significantly lower than for the positive control and all the batches inoculated with the different PSBs. Some of the isolates (PSB1, PSB5, PSB6, PSB7 and PSB9) were even capable of inducing greater height growth than that observed for the positive control plants ( Figure 3A). ...
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... the average dry weight of the negative control plant stems was the lowest, although significant differences were only observed regarding treatments with PSB1, PSB3, PSB5 and PSB9 ( Figure 3B). Negative control plants also exhibited a deficient spike maturation level, producing a high rate of green or immature ears ( Figure 4A and Figure S2). All the treatments were able to reverse this ear maturation deficiency, with significant differences for the PSB1, PSB2, PSB3, PSB5, PSB6, PSB7, PSB8 and PSB9 treatments. ...
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... determination of assimilated phosphorus levels demonstrated that plant stems of the positive controls had the highest phosphorus content, while negative controls showed the lowest phosphorus content among all the plants measured ( Figure 5A). Negative control plants also exhibited a deficient spike maturation level, producing a high rate of green or immature ears ( Figure 4A and Figure S2). All the treatments were able to reverse this ear maturation deficiency, with significant differences for the PSB1, PSB2, PSB3, PSB5, PSB6, PSB7, PSB8 and PSB9 treatments. ...
Similar publications
As the awareness on the ecological impact of chemical phosphate fertilizers grows, research turns to sustainable alternatives such as the implementation of phosphate solubilizing bacteria (PSB), which make largely immobile phosphorous reserves in soils available for uptake by plants. In this review, we introduce the mechanisms by which plants facil...
Citations
... For example, CAT levels are high to neutralize superoxide radicals, while POX activity is elevated to reduce H 2 O 2 . This relationship was interpreted using PCA-based biplot analysis of barley performance under stressful conditions (Figure 4) [106]. PCA biplot analysis performed for both physiological and biochemical traits identified relationships among traits under stressful conditions. ...
Salt stress is one of the most important abiotic stress factors that negatively affects sustainable crop production, agricultural productivity, and microbial life. Increasing salt stress negatively affects the growth and development of barley, posing a threat to global food security. It is now known that inoculation of plant growth-promoting rhizobacteria (PGPR) has significant potential in increasing stress tolerance and yield in agricultural products. This study focused on the effects of Bacillus cereus CUN6 and Bacillus thuringiensis SIRB2, isolated from the coastal zone and tested for their PGPR capacities, on physiological (root length, shoot length, biomass, dry weight) and biochemical (total chlorophyll, total protein, hydrogen peroxide, lipid peroxidation, peroxidase activity (POX), catalase activity (CAT)) analyses in Hordeum vulgare L. seedlings under salt stress. The results showed that the two bacterial inoculations alleviated the negative effects of salt stress by increasing the root-shoot length, biomass, dry weight, chlorophyll content, and total protein content in barley plants. However, B. thuringiensis increased growth and development especially in root length, biomass, and dry weight compared to B. cereus. On the other hand, B. cereus significantly increased root length, biomass, and chlorophyll content under salt stress; these increases were 17%, 5%, and 7%, respectively. B. thuringiensis chlorophyll content increased by 4% in 300 mM NaCl compared to the control. When compared in terms of the antioxidant defense system, B. thuringiensis inoculation was more effective on CAT activity, while B. cereus inoculation was more effective on POX activity. Under salt stress, B. cereus and B. thuringiensis inoculation significantly decreased H2O2 content in barley; these decreases were 16% and 10%, respectively. Additionally, TBARs content was significantly decreased by B. cereus and B. thuringiensis inoculation under salt stress; these decreases were determined as 8% and 9%, respectively, compared to the control. These results indicated that both bacterial inoculations can alleviate the salt tolerance of barley seedlings by regulating antioxidant metabolism. This research focused on the potential of B. cereus and B. thuringiensis as biofertilizers against salt stress in barley based on physiological and biochemical analysis.
... Rhizosphere soil Pigeon pea [153] Cultivated bulk soil NT [154] Cultivated bulk soil Rice [155] Cultivated bulk soil Corn, soybean, rice [156] Cultivated bulk soil Tea [157,158] Rhizosphere soil NT [159] Soybean rhizosphere Tomato [160] Rhizosphere soil Barley [161] Rhizosphere soil Rice [162] Rhizobia spp. Root nodules Soybean [163] Cultivated bulk soil NT [164] Root nodules Soybean [165] Root nodules Several legumes [166] Root nodules Common bean [6] Azospirillum spp. ...
Soil hosts diverse microbial communities including bacteria, fungi, archaea, protozoans and nematodes among others, which are fundamental to sustainable agriculture and drive essential processes that underpin soil fertility, plant health, and ecosystem resilience. They promote plant growth through mechanisms like nitrogen fixation, phosphorus solubilization, production of growth-promoting substances, enhancement of nutrient uptake, improvement of soil structure and detoxification of harmful substances. Recently, there has been increasing interest in utilizing microorganisms to improve soil health and boost plant growth and efficiency, despite limited understanding of microbial diversity, microbe-plant interactions, and translating laboratory findings to field conditions. This interest is driven by the urgent need to feed the growing global population, placing pressure on arable land to produce high-quality yields. Conventionally, synthetic fertilizers have been extensively used to provide nutrients, promote plant growth, and increase crop productivity. Although synthetic fertilizers have revolutionized agriculture since the green revolution, their overuse has significantly harmed soil health, and reduced crop productivity. This review synthesizes the current knowledge on the mechanisms by which soil microbes influence sustainable agricultural practices, with a focus on soil nutrient cycling and plant–microbe interactions. We discuss the functions and mechanisms of important microbial groups, such as nitrogen-fixing bacteria, phosphorus-solubilizing bacteria (PSB), and fungi. Furthermore, we discuss the factors that influence soil microbial communities and highlight gaps in future research to maximize their potential use in agriculture. Understanding the significance and key mechanisms of microbial communities increases the potential of harnessing soil microbes as vital contributors to soil health and sustainable agriculture.
... Barley is another crop that has shown positive effects following inoculation with P. fungorum (Ibáñez et al. 2021). The inoculation of barley seeds with strain PSB7, isolated from the barley rhizosphere, resulted in better phosphate accumulation in stems, greater dry weight, height of the aerial parts, and faster maturation of ears (Ibáñez et al. 2021). ...
... Barley is another crop that has shown positive effects following inoculation with P. fungorum (Ibáñez et al. 2021). The inoculation of barley seeds with strain PSB7, isolated from the barley rhizosphere, resulted in better phosphate accumulation in stems, greater dry weight, height of the aerial parts, and faster maturation of ears (Ibáñez et al. 2021). Direct PGP features of the strain were observed in vitro, including phosphate, zinc, and potassium solubilization and the production of siderophores, HCN, and IAA. ...
... Direct PGP features of the strain were observed in vitro, including phosphate, zinc, and potassium solubilization and the production of siderophores, HCN, and IAA. Inhibition of the plant pathogens Botrytis cinerea, F. oxysporum, Nigrospora oryzae, R. solani, and Alternaria alternata has also been identified for the strain PSB7 in agar plates (Ibáñez et al. 2021). However, there is no evidence of biocontrol in plants. ...
Agrochemicals are the primary alternative for maintaining the high yields necessary to produce sufficient plant-based foods to supply the world population. In recent decades, one of the most extensively explored alternatives to replace agrochemicals and reduce their environmental impact has been the use of microorganism-based products to boost crop yields with less environmental impact. This review focuses on the results of studies that have demonstrated the potential of the genus Paraburkholderia to increase crop yields and be utilized in biofertilizers and biocontrol products. A literature search was performed electronically considering articles and books published until August 19, 2024. We identified 24 species of Paraburkholderia with the ability to improve crop yields after their inoculation by different methods on seeds, seedlings, plantlets, adult crops, or fruits. The effects of these bacteria have been tested under laboratory, greenhouse, or field conditions. These Paraburkholderia species mediate their positive impact on crop growth by direct and indirect plant growth-promoting mechanisms, which include improving nutrient uptake, stimulating growth by phytohormone production, regulation and stimulation of metabolic pathways, induction of abiotic stress tolerance, and disease control by direct pathogen inhibition or induction of systemic resistance in plants. The literature reviewed here supports the use of Paraburkholderia in bio-inputs under the actual panorama of climate change and the necessity to increase sustainable agriculture worldwide.
... Is the world's fourth most extensively grown cereal, following wheat, rice, and corn. Around 70% of barley produced worldwide is utilized directly or indirectly for animal feed, with the remaining portion being used for malting and beer manufacture [16,17]. Compared to other cereal crops, barley is distinguished by its capacity to thrive in challenging environmental circumstances such salt and drought [18]. ...
Phosphorus is a vital element for all life forms. Phosphate-solubilizing bacteria transform phosphate into a bioavailable form through solubilization and mineralization processes. The aim of this study is evaluating the role of halotolerant, phosphate-solubilizing bacteria (PSB). having different PGPR traits as biofertilizers. Thirteen bacterial strains were isolated from soil samples of Ras Muhammad mangrove forest and screened for production of different PGPR traits. The most potent microbial Original Research Article Mussa et al.; Asian Soil Res. 125 candidates were identified by rRNA gene sequencing analysis and uploaded in GenBank as Bacillus safensis [OR341132] and Cytobacillus firmus [OR431197] these showed ability to tolerate salt concentration up to 10%, can fix nitrogen by growing on nitrogen free media with excellent growth and characterized qualitatively and quantitative solubilize phosphorous more than 100µg/ml of insoluble phosphate, hydrolyse phytate and produced IAA showing the highest value in the range of 94.54, 220,38 μg/mL respectively. In pot trials performed in a greenhouse the isolated strains Bacillus safensis [OR341132] and Cytobacillus firmus [OR431197] were able to significantly improve levels of assimilated phosphate, compared to non-inoculated plants. Moreover, mixed treatment (Bacillus safensis +Cytobacillus firmus) increased soil fertility and consequently improve the growth of parley plant. The study has overall concluded that bacteria isolated from mangrove soil, Bacillus safensis [OR341132] and Cytobacillus firmus [OR431197] could be used as the halotolerant plant growth-promoting rhizobacteria [HT-PGPR] and phosphate-solubilizing bacteria [PSB] and have a good influence on the health of barley [genotype Giza123] plants under salinity conditions during thirty days.
... These plates were incubated at 28 • C for 3 days and the relative bacterial colonies were selected based on the appearance of hyaline circles (Valetti et al., 2018). The isolates were subjected to successive purification steps and the purified strain was then stored in glycerol stock at −80 • C. The solubility index (SI) was determined by measuring hyaline circles and colony diameters at 4 days of culture according to the following formula: SI = (colony diameter + halo diameter)/(colony diameter) (Ibáñez et al., 2021). ...
Background
Plant growth-promoting rhizobacteria (PGPR) are an integral part of agricultural practices due to their roles in promoting plant growth, improving soil conditions, and suppressing diseases. However, researches on the PGPR in the rhizosphere of carrots, an important vegetable crop, is relative limited. Therefore, this study aimed to isolate and characterize PGPR strains from the rhizosphere soil of greenhouse-grown carrots, with a focus on their potential to stimulate carrot growth.
Methods
Through a screening process, 12 high-efficiency phosphorus-solubilizing bacteria, one nitrogen-fixing strain, and two potassium-solubilizing strains were screened. Prominent among these were Bacillus firmus MN3 for nitrogen fixation ability, Acinetobacter pittii MP41 for phosphate solubilization, and Bacillus subtilis PK9 for potassium-solubilization. These strains were used to formulate a combined microbial consortium, N3P41K9, for inoculation and further analysis.
Results
The application of N3P41K9, significantly enhanced carrot growth, with an increase in plant height by 17.1% and root length by 54.5% in a pot experiment, compared to the control group. This treatment also elevated alkaline-hydrolyzable nitrogen levels by 72.4%, available phosphorus by 48.2%, and available potassium by 23.7%. Subsequent field trials confirmed the efficacy of N3P41K9, with a notable 12.5% increase in carrot yields. The N3P41K9 treatment had a minimal disturbance on soil bacterial diversity and abundance, but significantly increased the prevalence of beneficial genera such as Gemmatimonas and Nitrospira. Genus-level redundancy analysis indicated that the pH and alkali-hydrolyzable nitrogen content were pivotal in shaping the bacterial community composition.
Discussion
The findings of this study highlight the feasibility of combined microbial consortium in promoting carrot growth, increasing yield, and enriching the root environment with beneficial microbes. Furthermore, these results suggest the potential of the N3P41K9 consortium for soil amelioration, offering a promising strategy for sustainable agricultural practices.
... Consequently, they release phosphorus into the soil by means of their capacity to solubilize organic and inorganic phosphorus. Previous research has shown that the rhizosphere contains a substantially higher population of phosphate solubilizing bacteria than non-rhizospheric soil (Linu et al., 2019;Ibáñez et al., 2021). Moreover, According to Anand et al. (2016), phosphorus solubilizing bacteria (PSB) are more efficient than fungal species in the solubilization of phosphorus, and make up 1-50% of the total microbial population in soil. ...
Phosphate-solubilizing bacteria, which are among the plant growth-promoting bacteria, dissolve insoluble phosphate in the soil by several pathways and promote plant growth. Therefore, it offers an alternative option instead of applying chemical fertilizers that disrupt soil chemistry and ecological balance. Although research on phosphate solubilizing bacteria has increased recently, the research on the peppermint and fennel rhizosphere is still limited. Investigating different rhizospheric local bacteria that can solubilize phosphate and replace chemical fertilizers is necessary. It was determined that 15 of the 53 bacterial isolates obtained from peppermint (Mentha piperita L.) and fennel (Foeniculum vulgare L.) rhizospheres formed a transparent (halo) region around the colonies on Pikovskaya Agar (PKA) medium using the MALDI-TOF MS method. The morphological, biochemical and IAA production of these isolates as well as quantitative measurements of phosphate solubilization by the isolates in NBRIP broth medium was evaluated. The highest efficiency was noted from Bacillus subtilis MMS-7 with solubilization value of 281.6 mg L-1. This was followed by Pseudomonas fluorescens MMS-11 with solubilization value of 263.4 mg L-1 and Bacillus thuringiensis MMS-3 with solubilization value of 172.1 mg L-1, respectively. Among the Phosphate solubilizing bacterial isolates, P solubilization index ranged 1.2-3.7 on PKA agar medium. Additionally, the highest IAA production was noted at 23.38 µg ml-1, using Bacillus subtilis MMS-7. This was followed by Pseudomonas fluorescens MMS-11 with value of 19.72 µg ml-1 and Bacillus thuringiensis using MMS-3 with value of 18.98 µg ml-1. This study demonstrated that selected local isolates can be used as effective phosphate-based microbial fertilizers.
... Serving as microbial inoculants, biofertilizers enhance soil physicochemical properties, microbial community diversity, and plant growth [3]. Useful microbial populations in agriculture include plant growth-promoting rhizobacteria (PGPR), N 2 -fixing cyanobacteria, plant disease-suppressive bacteria, oil-toxicant degrading microbes, and actinomycetes [4,5]. ...
... Although some studies have examined the effects on soil microorganisms, few have specifically investigated the rhizosphere microenvironment [20][21][22][23][24]. Therefore, further studies are necessary to investigate the responses of rhizosphere microbial communities in the coexistence of biofertilizers and MPs and enhance our understanding of the impact on the rhizosphere environment. For conventional MPs, MPs can change the features of soil (e.g., pH value, water evaporation, and aggregate stability) [5,25], microbial profiles (e.g., diversity, composition, and organic matter metabolic ability) [26], and the physicochemical properties of crops (e.g., biomass, growth, and root development) [2]. The interaction between Bio-MPs and biofertilizers and their impact on soil microecological characteristics are relatively unknown compared with conventional plastic particles. ...
Biodegradable microplastics (Bio-MPs) are a hot topic in soil research due to their potential to replace conventional microplastics. Biofertilizers are viewed as an alternative to inorganic fertilizers in agriculture due to their potential to enhance crop yields and food safety. The use of both can have direct and indirect effects on rhizosphere microorganisms. However, the influence of the coexistence of “Bio-MPs and biofertilizers” on rhizosphere microbial characteristics remains unclear. We investigated the effects of coexisting biofertilizers and Bio-MPs on the structure, function, and especially the carbon metabolic properties of crop rhizosphere bacteria, using a pot experiment in which polyethylene microplastics (PE-MPs) were used as a reference. The results showed that the existence of both microplastics (MPs) changed the physicochemical properties of the rhizosphere soil. Exposure to MPs also remarkably changed the composition and diversity of rhizosphere bacteria. The network was more complex in the Bio-MPs group. Additionally, metagenomic analyses showed that PE-MPs mainly affected microbial vitamin metabolism. Bio-MPs primarily changed the pathways related to carbon metabolism, such as causing declined carbon fixation/degradation and inhibition of methanogenesis. After partial least squares path model (PLS-PM) analysis, we observed that both materials influenced the rhizosphere environment through the bacterial communities and functions. Despite the degradability of Bio-MPs, our findings confirmed that the coexistence of biofertilizers and Bio-MPs affected the fertility of the rhizosphere. Regardless of the type of plastic, its use in soil requires an objective and scientifically grounded approach.
... In a study by Ibáñez et al. (2021), among 104 isolates obtained from the rhizospheres of the barley plant, Stenotrophomonas sp (AJK-9) and S. rhizophila (AJK-3) showed the maximum IAA (77.98 µg ml −1 , 72.32 µg ml −1 ) produced. Similarly, in our study, MH-54-4 (Stenotrophomonas sp.) also produced IAA (Table 4). ...
... Numerous studies have reported that the use of phosphate-solubilizing bacteria (PSBs) can increase the productivity of many different annual crops, such as barley, canola, maize, peanut, potato, sesame, sorghum, soybean, and wheat, among others [11,21,22,[24][25][26][27][28][29], as previously indicated in Section 1. However, to our knowledge, no data regarding the use of PSBs in perennial crops has been reported. ...
... The isolation of PSBs from the rhizosphere environment of hop plants indicated that 17.82% of the isolates could solubilize phosphate in solid NBRIP medium. This value was, however, considerably lower than the value of 61.5% of PSBs isolated from the rhizosphere of barley plants [21], which might suggest that the capability of different vegetable species to recruit PSBs to their rhizosphere could be different. The characterization of the 5 best phosphate solubilizers in solid NBRIP medium indicated that 4 of them (isolates ULE-PH1, ULE-PH5, ULE-PH6, and ULE-PH12) belonged to the Pseudomonas genus, whereas 1 belonged to the Bacillus genus (isolate ULE-PH10). ...
... The characterization of the 5 best phosphate solubilizers in solid NBRIP medium indicated that 4 of them (isolates ULE-PH1, ULE-PH5, ULE-PH6, and ULE-PH12) belonged to the Pseudomonas genus, whereas 1 belonged to the Bacillus genus (isolate ULE-PH10). Pseudomonas species were also the most frequently isolated PSBs from the rhizosphere of barley plants (9 out of the 17; 52.94%) [21], and the rhizosphere of shisham plants (7 out of 18 isolates; 38.89%) [49]. They were also dominant [50]. ...
Most of the phosphorus incorporated into agricultural soils through the use of fertilizers precipitates in the form of insoluble salts that are incapable of being used by plants. This insoluble phosphorus present in large quantities in soil forms the well-known “phosphorus legacy”. The solubilization of this “phosphorus legacy” has become a goal of great agronomic importance, and the use of phosphate-solubilizing bacteria would be a useful tool for this purpose. In this work, we have isolated and characterized phosphate-solubilizing bacteria from the rhizosphere of hop plants. Two particular strains, Pseudomonas taetrolens ULE-PH5 and Pseudomonas sp. ULE-PH6, were selected as plant growth-promoting rhizobacteria due to their high phosphate solubilization capability in both plate and liquid culture assays and other interesting traits, including auxin and siderophore production, phytate degradation, and acidic and alkaline phosphatase production. These strains were able to significantly increase phosphate uptake and accumulation of phosphorus in the aerial part (stems, petioles, and leaves) of hop plants, as determined by greenhouse trials. These strains are promising candidates to produce biofertilizers specifically to increase phosphate adsorption by hop plants.
... Another type of bacteria, namely Bacillus cereus, was shown to produce Indole Acetic Acid (IAA) (Zhou et al., 2021). The formation of a clear zone on National Botanical Research Institute's Phosphate (NBRIP) media around the colony is also an indication of the activity of phosphate-solubilizing bacteria (Ibáñez et al., 2021). Another collection, namely B. cereus RC76, the results of the in vitro antagonism test of isolates against Ralstonia syzygii subsp. ...
Shallot (Allium cepa var. aggregatum.) is a horticultural plant that is widely consumed in the world. However, the productivity of shallots in Indonesia is still relatively low, if compared to the actual optimum production potential of shallot. Shallot cultivation in Indonesia often experiences many problems. One of the problems is twisted diseases caused by Fusarium sp. This research aimed to study the effect of the application of organic material enriched with Bacillus in suppressing the development of twisted disease of shallot. This study was arranged in Randomized Complete Block Design (RCBD) with 5 treatments namely (A) compost + Bacillus velezensis isolate B-27, (B) compost + Bacillus cereus isolate RC76, (C) B. velezensis isolate B-27+B. cereus isolate RC76+compost, (D) compost + Trichoderma asperellum and (E) control (compost 1 ton/ha) with 5 replications on glasshouse treatment and 3 replications on field treatment. The results showed that the combination of B. velezensis in compost effectively reduced the incidence of twisted disease, the number of Fusarium spp. colonies, and the number of infected bulbs by Fusarium sp. Besides, the combination of compost with microbial agents showed better results than compost single treatment.
