Suppression Of Wilt Research Articles

Enhanced growth and suppression of fusarium wilt in Tomato plants through the action of Rhizophagus intraradices and Trichoderma viride

Enhanced growth and suppression of fusarium wilt in Tomato plants through the action of Rhizophagus intraradices and Trichoderma viride

Demonstration of the synergistic effect of biochar and Trichoderma harzianum on the development of Ralstonia solanacearum in eggplant.

Soil degradation has been accelerated by the use of chemical pesticides and poor agricultural practices, which has had an impact on crop productivity. Recently, there has been a lot of interest in the use of eco-friendly biochar applications to enhance soil quality and sequester carbon in sustainable agriculture. This study aimed to determine the individual and combined effects of Leaf Waste Biochar (LWB) and the bio-control agent Trichoderma harzianum (BCA) on the development of bacterial wilt in eggplants (Solanum melongena) caused by Ralstonia solanacearum (RS). The effects of LWB and BCA on eggplant physiology and defense-related biochemistry were comprehensively examined. Inoculated (+RS) and un-inoculated (-RS) eggplants were grown in potting mixtures containing 3% and 6% (v/v) LWB, both with and without BCA. The percentage disease index was considerably reduced (90%) in plants grown in the 6% LWB+ BCA amended treatments. Moreover, the plants grown in LWB and inoculated with BCA had higher phenolics, flavonoids and peroxidase contents compared to the non-amended control. The level of NPK was significantly increased (92.74% N, 76.47% P, 53.73% K) in the eggplants cultivated in the 6% LWB + BCA composition. This study has shown that the association of T. harzianum with biochar improved plant growth and reduced R. solanacearum induced wilt. Furthermore, the combined impact of biochar and T. harzianum was greater in terms of wilt suppression and increase in plant physiological measurements when the biochar concentration was 6%. Biochar and bio-control agents triggered biochemical alterations, thus enhancing the management of disease-infested soils.

Hollow Mesoporous Silica Nanoparticles as a New Nanoscale Resistance Inducer for Fusarium Wilt Control: Size Effects and Mechanism of Action.

In agriculture, soil-borne fungal pathogens, especially Fusarium oxysporum strains, are posing a serious threat to efforts to achieve global food security. In the search for safer agrochemicals, silica nanoparticles (SiO2NPs) have recently been proposed as a new tool to alleviate pathogen damage including Fusarium wilt. Hollow mesoporous silica nanoparticles (HMSNs), a unique class of SiO2NPs, have been widely accepted as desirable carriers for pesticides. However, their roles in enhancing disease resistance in plants and the specific mechanism remain unknown. In this study, three sizes of HMSNs (19, 96, and 406 nm as HMSNs-19, HMSNs-96, and HMSNs-406, respectively) were synthesized and characterized to determine their effects on seed germination, seedling growth, and Fusarium oxysporum f. sp. phaseoli (FOP) suppression. The three HMSNs exhibited no side effects on cowpea seed germination and seedling growth at concentrations ranging from 100 to 1500 mg/L. The inhibitory effects of the three HMSNs on FOP mycelial growth were very weak, showing inhibition ratios of less than 20% even at 2000 mg/L. Foliar application of HMSNs, however, was demonstrated to reduce the FOP severity in cowpea roots in a size- and concentration-dependent manner. The three HMSNs at a low concentration of 100 mg/L, as well as HMSNs-19 at a high concentration of 1000 mg/L, were observed to have little effect on alleviating the disease incidence. HMSNs-406 were most effective at a concentration of 1000 mg/L, showing an up to 40.00% decline in the disease severity with significant growth-promoting effects on cowpea plants. Moreover, foliar application of HMSNs-406 (1000 mg/L) increased the salicylic acid (SA) content in cowpea roots by 4.3-fold, as well as the expression levels of SA marker genes of PR-1 (by 1.97-fold) and PR-5 (by 9.38-fold), and its receptor gene of NPR-1 (by 1.62-fold), as compared with the FOP infected control plants. Meanwhile, another resistance-related gene of PAL was also upregulated by 8.54-fold. Three defense-responsive enzymes of POD, PAL, and PPO were also involved in the HMSNs-enhanced disease resistance in cowpea roots, with varying degrees of reduction in activity. These results provide substantial evidence that HMSNs exert their Fusarium wilt suppression in cowpea plants by activating SA-dependent SAR (systemic acquired resistance) responses rather than directly suppressing FOP growth. Overall, for the first time, our results indicate a new role of HMSNs as a potent resistance inducer to serve as a low-cost, highly efficient, safe and sustainable alternative for plant disease protection.

Bacillus methylotrophicus DCS1: Production of Different Lipopeptide Families, In Vitro Antifungal Activity and Suppression of Fusarium Wilt in Tomato Plants.

The present work aims to quantitatively and qualitatively monitor the production of lipopeptide mixtures by Bacillus methylotrophicus DCS1 strain in Landy medium and to investigate the antifungal activities of DCS1 strain and its produced lipopeptides. The in vitro activities were tested by the direct confrontation and agar well diffusion methods, while the in vivo study was carried out in order to test the efficiency of DCS1 bacterial suspension in the control of Fusarium wilt in tomato plants. Identification of lipopeptides by mass spectrometry (LC/MSD-TOF) showed that lipopeptide isoforms produced during the first 24h and 48h of fermentation are identical, belonging to bacillomycin D and fengycins A and B homologues with a difference in the yield of production. After 72h of fermentation corresponding to the end of incubation period, B. methylotrophicus DCS1 is able to produce a mixture of surfactin, pumilacidin, iturin A/mycosubtilin, iturin C1, bacillomycin D and fengycins A and B isoforms. The results of in vitro antifungal experiments suggest that B. methylotrophicus DCS1 has a significant potential as a biocontrol agent, owing to lipopeptides produced, endowed with antifungal activity against several phytopathogenic fungi. The curative treatment of tomato plants with DCS1 bacterial suspension was more effective in the protection against Fusarium oxysporum f. sp. radicis-lycopersici (FORL) than the preventive treatment by comparing the average number of leaves remaining healthy after 30days of each treatment and the appearance of tomato plants roots. The results indicate that B. methylotrophicus DCS1 exhibit a significant suppression of Fusarium wilt symptoms in tomato plants comparable to that of commercial fungicides and could be an alternative to chemically synthesized pesticides.

Evaluation of the Root Rupture Method for Controlling Belowground Spread of the Oak Wilt Pathogen (Bretziella fagacearum) in Northeast Wisconsin, USA

Abstract Oak wilt, caused by the pathogen Bretziella fagacearum, is a destructive disease on oak (Quercus) species in the United States. Established methods to control the belowground spread of oak wilt are not appropriate in all circumstances; thus, forest health managers have a strong need for alternative methods for disease control. We evaluated the effectiveness of operational stump excavation treatments (i.e., “root rupture” method) applied between 2004 and 2014 to control belowground spread of oak wilt on two forests in northeast Wisconsin, USA. The root rupture method achieved a high level of disease control (≥85% of evaluated disease infection centers) for 5 years by harvesting red oak trees within infection centers and uprooting the stumps and associated root mass. The likelihood of disease control success depended on the initial size of the infection center that was treated, with larger infection centers being less likely to be contained with a single treatment than small infection centers. This study highlights the importance of early detection and prompt management in oak wilt suppression programs. Study Implications: Forest management agencies and organizations in the North Central United States continue to face oak wilt epidemics. No single tool or treatment method ensures complete containment of oak wilt; thus, most managers carefully consider all the tools and techniques available to them and determine what best suits their budget and land use priorities. Stump excavation (i.e., “root rupture” method) is a cost-effective treatment for halting belowground spread of the oak wilt fungus, Bretziella fagacearum, that can achieve a high level of disease control. In northern red oak (Quercus rubra) stands with high economic value, this treatment can be applied as a group selection, with the value of the timber potentially offsetting the cost of treatment. The opportunity for complete disease control decreases as oak wilt infection centers increase in size; thus, monitoring and early control actions are critical.

Effectiveness of Bio-agent Formulations on Suppression of Lupine wilt Caused by Fusarium oxysporum f. sp. lupini

Effectiveness of Bio-agent Formulations on Suppression of Lupine wilt Caused by Fusarium oxysporum f. sp. lupini

Intercropping with Trifolium repens contributes disease suppression of banana Fusarium wilt by reshaping soil protistan communities

Fusarium wilt disease of bananas, caused by the soil-borne pathogen Fusarium oxysporum, threatens banana production. Intercropping, cultivation of more than one crop simultaneously on the same field, has emerged as efficient and sustainable land management for suppressing Fusarium wilt disease. Although previous studies have proven the changes in soil microbial communities including bacteria and fungi under intercropping contributed to disease suppression, little is known about the role of protistan communities in driving this effect. In a field experiment, we assessed microbiome shifts with a focus on protists under intercropping of banana with the legume Trifolium repens. Our results showed that the reduced Fusarium wilt disease incidence and the decreased Fusarium pathogen density under intercropping could be attributed to the changes in protistan community compositions. Specially, we observed a significant negative correlation between the relative abundance of phagotrophic protists and Fusarium oxysporum. We further conducted a pot experiment to examine the impacts of the legume crop on phagotrophic protists across different spatial distances, which showing that intercropping enriched the relative abundance of phagotrophic protists, especially Cercomonas, with members of this group showing the capacity to directly inhibit the growth of Fusarium pathogen in vitro. We highlight that predatory protists are important agents underlying disease suppression in intercropping system, which can offer new venues to promote plant health in sustainable agriculture.

Testing a biocontrol agent consortium for suppression of tomato bacterial wilt through rhizosphere microecological regulation

Tomato bacterial wilt (TBW) caused by Ralstonia solanacearum leads to severe crop losses. The aim of the present study was to construct a biocontrol agent consortium (BAC) and evaluate its efficiency against TBW. Bacillus tequilensis FJAT-51047 and Streptomyces fradiae FJAT-31535 were isolated from healthy tomato rhizosphere soils and had intense antagonistic ability against R. solanacearum and high control efficiency against TBW. The mixture of fermentation broths of FJAT-1458 (an avirulent strain of R. solanacearum), FJAT-51047 and FJAT-31535 with a ratio (v:v:v) of 1:1:1 had the highest control efficiency of 100 % in a pot experiment and was used as the BAC. When it was applied in a 6-year continuous cropping field, the BAC could (1) enhance soil organic carbon, total nitrogen and phosphorus, and total potassium contents by 34.18, 38.46, 115.44, and 17.41 %, respectively, at the reproductive stage; (2) increase soil urease activity by 36.54 and 9.63 % at the vegetative and reproductive stages, respectively; (3) increase tomato yield by 113.46 %; and (4) reach a control efficiency of 84.10 %. The BAC significantly enriched rhizosphere soil with the beneficial bacteria Bauldia, Altererythrobacter, Pseudolabrys, Ferruginibacter and Rhodoplanes, and inhibited the pathogen-related bacteria Ralstonia and Aquicella. Redundancy analysis revealed a negative relationship between rhizosphere soil physicochemical parameters (pH, SOC, TN, TP and TK) and TBW disease incidence (DI) or the R. solanacearum population. Overall, BAC could be used for microecological regulation of the tomato rhizosphere to control TBW.

Effect of raw material and application rate of biogas slurry on Cucumber growth, Fusarium wilt suppression, and soil properties

With the popularization and application of biogas engineering, byproduct biogas slurry has excellent application potential as organic liquid fertilizer, while its source and application rate significantly affect its effect. Irrational application of biogas slurry, can reduce crop yields and cause environmental problems such as soil salinization and diffuse source pollution. In this study, the impact of different types of biogas slurry from various materials (i.e., pig manure, chicken manure, vinasse, and kitchen waste) and their required application rates on the growth and incidence of cucumber were investigated by analyzing the dry weight of cucumber, soil chemical properties, soil extracellular enzyme activity, and the incidence of cucumber wilt disease. The results showed that the effects of the four selected types of biogas slurry on cucumber growth and disease were similar. It was shown that 3% was the most suitable application rate considering the dry weight of cucumber plants and the incidence of wilt disease. At this application rate, it was achievable to increase soil pH, soil AN, AK, Olsen P content, and enzyme activities without increasing the risk of salinization. In summary, despite different sources, biogas slurry showed the best growth promotion and disease suppression ability in 3% (v/w) application, without the risk of soil salinization.

Bioagents Induced Resistance to Ceratocystis fimbriata in Pomegranate

Pomegranate is the most important fruit crop consumed in the world. In India the plant is cultivated in almost all agroecological areas, however, yields remain low due to attacks by various pathogens and insects. Among the pathogens, wilt caused by Ceratocystis fimbriata is an important disease and its soil-borne pathogen is difficult to manage. To contribute to the control of this microbial pathogen, the stimulatory effect of the Pomegranate defense system of bioagents in the pomegranate interaction was evaluated. Resistance-inducing rhizobacteria offer an excellent alternative in providing natural, effective, safe, persistent, and durable protection. Plants have endogenous defense mechanisms that can be induced in response to the pathogen and bio-agents. The increased activities of the defense enzymes, viz. peroxidase (PO), polyphenol oxidase (PPO), phenylalamine ammonia lyase (PAL), and phenolic compounds in the bio-agents treated plants of pomegranate challenged with C. fimbriata were recorded in the present studies. The maximum activity of defense enzymes viz., peroxidase, polyphenol oxidase, phenylalanine ammonia-lyase and total phenol was recorded in diamond (T. viride) followed by T. harzianum (Th-R) and Platinum (P. fluorescens) indicating the role of bio-agents in increasing the role of defense enzymes in suppression of wilt.

Suppression of tomato wilt by cell-free supernatants of Acinetobacter baumannii isolates from wild cacao from the Colombian Amazon

Tomato vascular wilt caused by Fusarium oxysporum f. sp. lycopersici (Fol) is one of the most limiting diseases of this crop. The use of fungicides and varieties resistant to the pathogen has not provided adequate control of the disease. In this study, siderophore-producing bacteria isolated from wild cocoa trees from the Colombian Amazon were characterized to identify prominent strategies for plant protection. The isolates were taxonomically classified into five different genera. Eight of the fourteen were identified as bacteria of the Acinetobacter baumannii complex. Isolates CBIO024, CBIO086, CBIO117, CBIO123, and CBIO159 belonging to this complex showed the highest efficiency in siderophore synthesis, producing these molecules in a range of 91–129 µmol/L deferoxamine mesylate equivalents. A reduction in disease severity of up to 45% was obtained when plants were pretreated with CBIO117 siderophore-rich cell-free supernatant (SodSid). Regarding the mechanism of action that caused antagonistic activity against Fol, it was found that plants infected only with Fol and plants pretreated with SodSid CBIO117 and infected with Fol showed higher levels of PR1 and ERF1 gene expression than control plants. In contrast, MYC2 gene expression was not induced by the SodSid CBIO117 application. However, it was upregulated in plants infected with Fol and plants pretreated with SodSid CBIO117 and infected with the pathogen. In addition to the disease suppression exerted by SodSid CBIO117, the results suggest that the mechanism underlying this effect is related to an induction of systemic defense through the salicylic acid, ethylene, and priming defense via the jasmonic acid pathway.Graphical abstract

Bacterial wilt suppressive composts: Significance of rhizosphere microbiome

Composts are often suppressive to several plant diseases, including the devastating bacterial wilt caused by Ralstonia solanacearum. However, the underlying mechanisms are still unclear. Herein, we carried out an experiment with 38 composts collected from different factories in China to study the interlinking among bacterial wilt suppression, the physicochemical properties and bacterial community of the compost, and bacterial community in the rhizosphere of tomato fertilized by compost. Totally 26 composts were suppressive to bacterial wilt, while six composts stimulated the disease. The control efficiency was neither correlated with physicochemical properties (TC, TN, P and K, pH or GI) nor bacterial community of compost, but with rhizosphere bacterial community (r = 0.17, p = 0.016). The control efficiency was also positive correlated with taxa (Rhizobium, Aeromicrobium) known suppressive to R. solanacearum. The mushroom spent or cow manure, from which the two composts were 100% and 77% in control efficiencies against bacterial wilt respectively were subject to a pilot-scale composting reaction. The reproduced composts from mushroom spent or cow manure were only 57% and 23% effective on the control of bacterial wilt, respectively. The analysis of bacterial communities revealed that the relative abundances of R. solanacearum were 28.4% for the control, but only 7.8%-7.9% for compost fertilized tomatoes. The compost from mushroom spent also exerted a strong effect on rhizosphere bacterial community. Taken together, most composts were suppressive to bacterial wilt possibly also by modifying rhizosphere bacterial community towards inhibiting the colonization of R. solanacearum and selecting for beneficial genera of Proteobacteria, Bacteroidetes and Actinobacteria.

Salicylic acid-doped iron nano-biostimulants potentiate defense responses and suppress Fusarium wilt in watermelon

IntroductionChemo- and bio-genic metallic nanoparticles (NPs), as a novel nano-enabled strategy, have demonstrated a great potential in crop health management. ObjectiveThe current study aimed to explore the efficacy of advanced nanocomposites (NCs), integrating biogenic (bio) metallic NPs and plant immunity-regulating hormones, in crop disease control. MethodsIron (Fe) NPs were biosynthesized using cell-free supernatant of a Fe-resistant strains, Bacillus marisflavi ZJ-4. Further, salicylic acid-coated bio-FeNPs (SI) NCs were prepared via co-precipitation method under alkaline conditions. Both bio-FeNPs and SINCs were characterized using basic analytical techniques, including Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction analysis, and scanning/transmission electron microscopy. ResultsBio-FeNPs and SINCs had variable shapes with average sizes of 72.35 nm and 65.87 nm, respectively. Under greenhouse conditions, bio-FeNPs and SINCs improved the agronomic traits of the watermelon plants, and SINCs outperformed bio-FeNPs, providing the maximum growth promotion of 32.5%. Soil-drenching with bio-FeNPs and SINCs suppressed Fusarium oxysporum f. sp. niveum-caused Fusarium wilt in watermelon, and SINCs provided better protection than bio-FeNPs, through inhibiting the fungal invasive growth within host plants. SINCs improved the antioxidative capacity and primed a systemic acquired resistance (SAR) response via activating the salicylic acid signaling pathway genes. These findings indicate that SINCs can reduce the severity of Fusarium wilt in watermelon by modulating antioxidative capacity and potentiating SAR to restrict in planta fungal invasive growth. ConclusionThis study provides new insights into the potential of bio-FeNPs and SINCs as biostimulants and bioprotectants for growth promotion and Fusarium wilt suppression, ensuring sustainable watermelon production.

Cyclic Lipopeptides of Bacillus amyloliquefaciens DHA6 Are the Determinants to Suppress Watermelon Fusarium Wilt by Direct Antifungal Activity and Host Defense Modulation.

Fusarium wilt, caused by Fusarium oxysporum f. sp. niveum (Fon), poses a serious threat to watermelon productivity. We previously characterized six antagonistic bacterial strains, including DHA6, capable of suppressing watermelon Fusarium wilt under greenhouse conditions. This study investigates the role of extracellular cyclic lipopeptides (CLPs) produced by strain DHA6 in Fusarium wilt suppression. Taxonomic analysis based on the 16S rRNA gene sequence categorized strain DHA6 as Bacillus amyloliquefaciens. MALDI-TOF mass spectrometry identified five families of CLPs, i.e., iturin, surfactin, bacillomycin, syringfactin, and pumilacidin, in the culture filtrate of B. amyloliquefaciens DHA6. These CLPs exhibited significant antifungal activity against Fon by inducing oxidative stress and disrupting structural integrity, inhibiting mycelial growth and spore germination. Furthermore, pretreatment with CLPs promoted plant growth and suppressed watermelon Fusarium wilt by activating antioxidant enzymes (e.g., catalase, superoxide dismutase, and peroxidase) and triggering genes involved in salicylic acid and jasmonic acid/ethylene signaling in watermelon plants. These results highlight the critical roles of CLPs as determinants for B. amyloliquefaciens DHA6 in suppressing Fusarium wilt through direct antifungal activity and modulation of plant defense responses. This study provides a foundation for developing B. amyloliquefaciens DHA6-based biopesticides, serving as both antimicrobial agents and resistance inducers, to effectively control Fusarium wilt in watermelon and other crops.

Synergistic effects of arbuscular mycorrhizal fungi associated to plant growth-promoting rhizobacteria in suppression of soil-borne Fusarium wilt of date palm

Soil-borne Fusarium wilt represents one of the major problems in the cultivation of the date palm. Arbuscular mycorrhizal fungi (AMF) consortium and plant growth-promoting rhizobacteria (PGPR) consortium were tested to determine the efficacy in disease management of Fusarium wilt. When applied individually, PGPR or AMF consortium reduced disease incidence, disease severity, and mortality rate of date palm seedlings. The combination of these consortia showed the best control efficiency which reflects a significant synergistic effect. The decrease in disease progression was accompanied by a significant promotion of plant immunity through the activation of the phenylpropanoid pathway, which was concreted by enhancement of PAL activity and accumulation of polyphenols and lignin content in date palm roots. In vitro antagonistic tests against Fusarium. oxysporum f. sp. albedinis (Foa) revealed that the bacterial strains of the PGPR consortium inhibited Foa growth, particularly the strain Bacillus cereus strain 263AG5' (60.59%). The evaluation of the mycorrhizal status of date palm roots after 27 weeks following the inoculation with Foa showed that the addition of both consortia was accompanied by a 3-fold increase in the intensity of mycorrhization and the arbuscules and vesicles number and 1.5 times increase in the frequency of mycorrhization. Our results highlight the high synergistic effect between PGPR and AMF consortia in date palm protection against Foa that could be attributed to the association of their antagonistic effect with their strong capacity for stimulation of plant natural defenses which suggests that these PGPR/AMF could be an effective approach to pathogen suppression.

Suppression of Fusarium Wilt in Watermelon by Bacillus amyloliquefaciens DHA55 through Extracellular Production of Antifungal Lipopeptides

Fusarium wilt caused by Fusarium oxysporum f. sp. niveum is one of the most devastating fungal diseases affecting watermelon (Citrullus lanatus L.). The present study aimed to identify potent antagonistic bacterial strains with substantial antifungal activity against F. oxysporum f. sp. niveum and to explore their potential for biocontrol of Fusarium wilt in watermelon. Out of 77 isolates from watermelon rhizosphere, six bacterial strains-namely, DHA4, DHA6, DHA10, DHA12, DHA41, and DHA55-exhibited significant antifungal activity against F. oxysporum f. sp. niveum, as well as other phytopathogenic fungi, including Didymella bryoniae, Sclerotinia sclerotiorum, Fusarium graminearum, and Rhizoctonia solani. These Gram-positive, rod-shaped, antagonistic bacterial strains were able to produce exo-enzymes (e.g., catalase, protease, and cellulase), siderophore, and indole-3-acetic acid and had the ability to solubilize phosphate. In greenhouse experiments, these antagonistic bacterial strains not only promoted plant growth but also suppressed Fusarium wilt in watermelon. Among these strains, DHA55 was the most effective, achieving the highest disease suppression of 74.9%. Strain DHA55 was identified as Bacillus amyloliquefaciens based on physiological, biochemical, and molecular characterization. B. amyloliquefaciens DHA55 produced various antifungal lipopeptides, including iturin, surfactin, and fengycin, that showed significant antifungal activities against F. oxysporum f. sp. niveum. Microscopic observations revealed that B. amyloliquefaciens DHA55 exhibited an inhibitory effect against F. oxysporum f. sp. niveum on the root surface of watermelon plants. These results demonstrate that B. amyloliquefaciens DHA55 can effectively promote plant growth and suppress the development of watermelon Fusarium wilt, providing a promising agent for the biocontrol of Fusarium wilt in watermelon.

Lanthanum-based nanomaterials suppress bacterial wilt in tomato: importance of particle morphology and dissolution profiles

Particle morphology and dissolution profile determine the suppression of bacterial wilt in tomato by lanthanum-based nanomaterials.

Suppression of Fusarium Wilt of Chickpea by Bacillus spp., Pseudomonas sp. and Rhizobacterial Isolate

This experiment was conducted to evaluate the antagonistic effects of some selected rhizobacteria on Fusarium oxysporium f. sp. ciceris in a pot experiment. Rhizobacterial isolates (one isolate of Pseudomonas, eight isolates of Bacillus genera and one bacterium isolate) and two chickpea cultivars (Shendi and Burgeig) were arranged in a factorial pot experiment in CRD with four replicates. The disease incidence and severity were detected weekly. Disease reduction percentage was estimated at the end of the study. Generally, the application of rhizobacterial isolates as biological control agent reduced disease incidence compared with the control in both cultivars. The incidence in cultivar Shendi occurred at the third week after inoculation when treated with Pseudomonas stutzeri strain W28 (SA3) and Bacillus subtilis strain CM14(SA9). For the two cultivars, Shendi and Burgeig, the Geobacillus sp. CRRI-HN-1(SA2) and Bacillus sp (SA1), respectively had the highest positive effect on disease incidence and severity throughout the experiment compared with the control. These were 45.36 and 44.82% in incidence; 55.36 and 63.89% in severity, respectively.

Fluorine-containing amphiphilic quaternary ammonium salts for the suppression of Banana fusarium wilt

As the pathogen of banana Fusarium wilt, Fusarium oxysporum f. sp. cubense race 4 (Foc4) has the strongest toxicity and pathogenicity due to its long-term viability in soil, but there is still no effective way to control it at present. Based on the activity parameters of polymeric quaternary ammonium salt in our previous work, this paper hopes to enhance the amphiphilicity of polymeric quaternary ammonium salt by introducing a fluoroalkyl group to improve the antifungal property of polymeric quaternary ammonium salt and achieve stable adsorption and long-term inhibition of saprophytic Foc4 conidia in soil. Here, we prepared a series of fluorine-containing ammonium salts with random and block structures by atom transfer radical polymerization (ATRP), and we systematically studied the effects of the introduction of fluoroalkyl groups, the proportion of hydrophobic segments and polymer structure on micelle properties, antifungal properties, adsorption, migration and long-term antifungal properties against Foc4 in soil. Finally, the preferred polymeric quaternary ammonium salts were selected for pot experiments in the prevention and control of banana Fusarium wilt caused by Foc4, and positive experimental results were achieved. In conclusion, we made an exploratory attempt at the practical application of polymeric amphiphilic quaternary ammonium salt in plant disease control.

Suppression of Tomato Bacterial Wilt Incited by Ralstonia pseudosolanacearum Using Polyketide Antibiotic-Producing Bacillus spp. Isolated from Rhizospheric Soil

Bacillus spp. has the potential to control bacterial and fungal diseases of crops. In vitro study, Bacillus amyloliquefaciens DSBA-11 showed best to inhibit the growth of Ralstonia pseudosolanacearum as compared to Bacillus cereus JHTBS-7, B. pumilus MTCC-7092, B. subtilis DTBS-5 and B. licheniformis DTBL-6.Three primers sets from nucleotide sequences of polyketide antibiotic synthase genes viz., macrolactin, difficidin and bacillaene of B. amyloliquefaciens FZB42 were designed and standardized protocol for simultaneous detection of polyketide antibiotics-producing strains of Bacillus spp. by multiplex—PCR with products size of 792 bp, 705 bp and 616 bp respectively. All the strains of B. amyloliquefaciens contained three polyketide antibiotic synthase genes, and B. subtilis possessed difficidin and macrolactin, whereas B. cereus JHTBS-7, B. pumilus MTCC-7092 and B. licheniformis DTBL-6 did not contain any polyketide antibiotic genes. By using this technique, polyketide-producing strains of Bacillus spp. were screened within a short period with high accuracy. These polyketide synthase genes were cloned by using a T&A vector to study the role of these genes in producing antibiotics that suppressed the growth of R. pseudosolanacearum under both in vitro and in vivo conditions. Bio-efficacy of cloned products of these genes macrolactin, bacillaene, and difficidin along with parent strain B. amyloliquefaciens DSBA-11 inhibited the growth of R. pseudosolanacearum and formed 1.9 cm2, 1.9 cm2, 1.7 cm2 and 3.3 cm2 inhibition area under in vitro conditions respectively. Minimum bacterial wilt disease intensity (29.3%) with the highest biocontrol efficacy (57.72%) was found in tomato cv. Pusa Ruby (susceptible to wilt disease) was treated with B. amyloliquefaciens DSBA-11 followed by cloned products of difficidin and macrolactin under glasshouse conditions. Hence, the developed multiplex protocol might be helpful for screening polyketide antibiotics producing potential strains of Bacillus spp. from soil which can apply for managing the wilt disease of tomatoes. The polyketide antibiotics produced by bacteria might have a significant role suppression of R. pseudosolanacearum due to the disintegration of cells.