Sclerotium Cepivorum Research Articles

Evaluation of Garlic Accessions for Their Yield, Yield Components, and White Root Rot (Sclerotium cepivorum Berk) in the Southern Zone of Tigray, Ethiopia

Evaluation of Garlic Accessions for Their Yield, Yield Components, and White Root Rot (Sclerotium cepivorum Berk) in the Southern Zone of Tigray, Ethiopia

Management of onion white rot caused by Sclerotium cepivorum Berk using bio-synthesized silver nanoparticles

Management of onion white rot caused by Sclerotium cepivorum Berk using bio-synthesized silver nanoparticles

Nanoparticles and Chemical Inducers: A Sustainable Shield against Onion White Rot.

This study investigated the effectiveness of nanoparticles and chemical inducers in managing onion white rot caused by Sclerotium cepivorum. The pathogen severely threatens onion cultivation, resulting in significant yield losses and economic setbacks. Traditional fungicides, though effective, raise environmental concerns, prompting a shift toward eco-friendly alternatives. In this study, four S. cepivorum isolates were utilized, each exhibiting varying degrees of pathogenicity, with the third isolate from Abu-Hamad demonstrating the highest potency. During the in vitro studies, three nanoparticles (NPs) were investigated, including Fe3O4 NPs, Cu NPs, and ZnO NPs, which demonstrated the potential to inhibit mycelial growth, with salicylic acid and Fe3O4 NPs exhibiting synergistic effects. In vivo, these nanoparticles reduced the disease incidence and severity, with Fe3O4 NPs at 1000-1400 ppm resulting in 65.0-80.0% incidence and 80.0-90.0% severity. ZnO NPs had the most positive impact on the chlorophyll content, while Cu NPs had minimal effects. At 1000 ppm, Fe3O4 NPs had variable effects on the phenolic compounds (total: 6.28, free: 4.81, related: 2.59), while ZnO NPs caused minor fluctuations (total: 3.60, free: 1.82, related: 1.73). For the chemical inducers, salicylic acid reduced the disease (10.0% incidence, 25.0% to 10.0% severity) and promoted growth, and it elevated the chlorophyll values and enhanced the phenolic compounds in infected onions. Potassium phosphate dibasic (PDP) had mixed effects, and ascorbic acid showed limited efficacy toward disease reduction. However, PDP at 1400 ppm and ascorbic acid at 1000 ppm elevated the chlorophyll values and enhanced the phenolic compounds. Furthermore, this study extended to traditional fungicides, highlighting their inhibitory effects on S. cepivorum. This research provides a comprehensive comparative analysis of these approaches, emphasizing their potential in eco-friendly onion white rot management.

Encapsulation of garlic oil and diallyl disulfide with β-cyclodextrin for white rot control in Allium crops

White rot, caused by Sclerotium cepivorum, is a devastating disease of onion, garlic, and other Allium crops. The pathogen reproduces and survives by forming sclerotia, which can survive in field soils for decades. The pathogen is host-specific to Allium spp., and sclerotia germinate in response to sulfur compounds produced by Allium roots. Sulfur-containing compounds such as diallyl disulfide (DADS) and garlic oil can stimulate sclerotia germination and effectively reduce pathogen populations before planting an Allium crop; however, these compounds are often highly volatile and difficult to handle and apply. Therefore, a study was conducted to encapsulate DADS and garlic oil with β-cyclodextrin (β-CD) to protect sulfur volatiles from interactions with soil and against oxidation, degradation, and evaporation. Microcapsule extract analysis showed that garlic oil and DADS were successfully encapsulated with greater than 90% recovery of the starting product. In addition, the micro-encapsulation process did not change the chemical compounds, but their proportions were altered. Furthermore, lab and growth chamber incubation experiments revealed that DADS and DAS could be slowly released into the soil from microcapsules and worked effectively for white rot sclerotia germination. Compared to the non-treated control, liquid DADS, microcapsules of DADS, and microcapsules of garlic oil reduced sclerotia populations by between 73.7 and 82.3%, depending on the treatment. When compared to liquid DADS and garlic oil, the encapsulated formulations DADS and garlic oil are equally effective but easier to handle, which can provide more flexibility in terms of timing, placement, and method of sclerotia germination stimulant applications.

Evaluation of Bait Crops for the Integrated Management of White Rot (Sclerotium cepivorum) in Allium Crops.

White rot, caused by Sclerotium cepivorum, is a serious disease that causes significant yield losses in Allium production. The pathogen persists in soil as sclerotia, which germinate in response to sulfur compounds in Allium root exudates. This study was aimed at investigating the potential of early-terminated Allium bait crops to reduce densities of S. cepivorum sclerotia in soil. In growth chamber experiments with white onion (A. cepa cultivar 'Southport White Globe'), red onion (A. cepa cultivar 'Marenge'), sweet onion (A. cepa cultivar 'Walla Walla'), and bunching onion (A. fistulosum cultivar 'Parade'), termination of all four Alliums at the first- and second-leaf stages reduced soil sclerotia populations by up to 62 and 76%, respectively. Examination of soil samples collected 4 weeks after crop termination indicated that sclerotia populations in bait crop treatments remained low when seedlings were terminated at the first- and second-leaf stages. In contrast, crop termination at the third-leaf stage resulted in an increase in sclerotia counts due to the pathogen reproduction on the bait crops. The reduction in sclerotia populations in soil due to early crop termination was also observed in replicated field trials. Greater reductions in sclerotia counts were observed when plants in these experiments were terminated chemically as opposed to mechanically. In-furrow fungicides did not reduce sclerotia numbers under the conditions tested. This study demonstrates the potential for early termination of Allium bait crops to help reduce white rot inoculum in soil.

Enhanced white rot control in garlic bulbil using organic-inorganic hybrid materials as coating membranes.

Organic-inorganic hybrid materials have a range of applications due to their unique properties. Their application in agriculture brings alternatives for the controlled release of nutrients in the soil, the seed coating, the transport of herbicides, and the treatment of plant diseases. The present study aimed to investigate the use of fungicides incorporated into hybrid membranes formed by synthetic hectorite (LAPONITE®) and polymers in the pre-treatment of garlic bulbils exposed to the pathogen Stromatinia cepivora, which causes white rot. The coatings were selected by a germination test, based on the bulbil sprouting index, and by a mycelial growth inhibition test, based on the percentage of mycelial growth inhibition. The chosen membranes were used to coat the bulbils for bioassays conducted in a biochemical oxygen demand incubator at 17 °C. The coated bulbils were planted in soil samples containing three different densities of Stromatinia cepivora: 0.1 g, 1.0 g, and 10 g of sclerotium per L of soil. Membranes containing 2% carboxymethyl cellulose and 2% LAPONITE® incorporated with (i) the fungicide tebuconazole (36 mg L-1) and (ii) the combination of the actives tebuconazole (36 mg L-1) and triadimenol (62 mg L-1) showed the total rate of sprouting and null indices of incidence of symptoms and mortality in its repetitions. The hybrid membranes were characterized employing several techniques, including X-ray diffraction, infrared and Raman spectroscopy, thermogravimetric analysis and differential scanning calorimetry coupled to mass spectrometry, and optical microscopy. Characterization data confirmed the presence of fungicides incorporated into the membranes. Some concentrations of fungicides were low enough not to be detected in all analyses performed, although they guaranteed a protective character to the bulbils about the fungus S. cepivora present in the soil, with a possibility of antifungal pre-treatment with a potential reduction in the concentration used.

Suppression of White Rot of Welsh Onion by a Preplant Transplant Drench Using Pyraziflumid

White rot, caused by Sclerotium cepivorum, poses a significant threat to the production of Welsh onions. This study aimed to quantitatively assess the effectiveness and persistence of pyraziflumid when applied via a preplant transplant drench. Six trials were conducted across five fields from 2020 to 2021. A day before planting, each paper pot tray was drenched with 500 ml of 2.2 g/liter of pyraziflumid. In the untreated Welsh onions, the disease was first observed in November in all trials. Subsequently, the disease incidence increased rapidly, and by January, nearly all plants were affected. Conversely, in the pyraziflumid-drenched trials, the disease was barely observed until January. The generalized linear mixed model analysis revealed that the estimated coefficient for the pyraziflumid drench was −5.37 compared with no drench, significantly reducing disease incidence. The odds ratio was 0.005, indicating that the pyraziflumid drench significantly reduced the disease incidence compared with no treatment. The linear mixed model analysis showed that the pyraziflumid drench significantly increased the yield of Welsh onion by 3.6 kg/10 A in plots infested with the disease. This, despite requiring only one drench before planting, demonstrated excellent disease-suppressive effects and proved to be extremely labor-saving and economical.

Two Bacterial Bioagents Boost Onion Response to Stromatinia cepivora and Promote Growth and Yield via Enhancing the Antioxidant Defense System and Auxin Production

White rot, caused by Stromatinia cepivora (Anamorph: Sclerotium cepivorum Berk), is a serious soil-borne disease of the onion that restricts its cultivation and production worldwide. Herein, we isolated and characterized a plant growth-promoting rhizobacterium Stenotrophomonas maltophilia from healthy onion roots and an endophytic bacterium Serratia liquefaciens from healthy bean leaves. Both isolates showed strong fungistatic activity against S. cepivora using the dual culture and culture filtrate methods. This effect might be due to the presence of several volatile compounds, especially menthol in both culture filtrates as shown with a GC-MS analysis. Additionally, the root drench application of cell-free culture filtrates of S. maltophilia and S. liquefaciens significantly reduced the incidence and severity of white rot disease on treated onion plants, which was associated with the activation of both enzymatic (POX and PPO) and non-enzymatic (phenolics and flavonoids) antioxidant defense machineries of S. cepivora-infected onion plants. Moreover, the culture filtrates of both bacterial bioagents remarkably enhanced the growth (as expressed by root length, plant height, and number of leaves) and yield parameters (as indicated by bulb circumference, fresh weight of the bulb, and bulb yield per plot) of treated onion plants under field conditions during two successive seasons (2020/2021 and 2021/2022). This might be because of a reduced disease severity and/or the accumulation of the main auxin, indole-3-acetic acid (IAA), and its precursor, the amino acid tryptophan. Our findings suggest that both bioagents might be utilized as eco-friendly alternative control measures to reduce the utilization of chemical fungicides entirely or partially for the safer production of onion in S. cepivora-infested soils.

Biological control of onion white rot disease using potential Bacillus subtilis isolates

BackgroundOnion (Allium cepa L.) is a very important vegetable crop all over the world, particularly in Egypt for local consumption and exportation. White rot disease is the most serious disease of Allium spp. caused by the soil-borne fungus Sclerotium cepivorum Berk.ResultsIn this investigation, five tested isolates of Bacillus subtilis showed an antagonistic effect and significantly reduced the linear growth of the pathogen in vitro. B. subtilis isolates no. 2 and 4 caused the highest reduction of S. cepivorum growth, 75.78 and 74.33%, respectively, while isolate no. 3 was the least effective one, causing 66.67% growth reduction. Under field conditions at two successive seasons (2019/20 and 2020/21), all tested bioagent treatments reduced the percentage of infection than Folicure as an officially recommended fungicide. B. subtilis isolate no. 2 showed the highest efficacy (78.57 and 77.78%) followed by isolates no. 4 (74.29 and 72.22%), while B. subtilis isolate no. 3 showed the lowest efficacy (42.86 and 50.00%), respectively, for both successive seasons. All treatments increased dry onion bulb yield and improved its quality than the untreated control plants. The chemical changes of total carbohydrates, total nitrogen contents, total soluble solids (TSS %) and enzymes activity related to defense mechanisms in treated plants by biological treatments were considered.ConclusionThis study aimed to find effective biological agents of B. subtilis isolates against the white rot of onion and evaluate their effect on yield parameters, components and quality.

Trichoderma longibrachiatum, a biological control agent of Sclerotium cepivorum on onion plants under salt stress

Salt stress and pathogen infection cause damage to onion crops and limit production. Application of Trichoderma species could be an option for reducing crop damage. The objective of this work was to evaluate the capacity of Trichoderma longibrachiatum to reduce damage to onion plants caused by salinity and infection by Sclerotium cepivorum. The two fungi showed differences in their tolerance to NaCl depending on the NaCl concentration. At low concentrations of NaCl, S. cepivorum was more tolerant than T. longibrachiatum, while at high concentrations of NaCl the tolerance of T. longibrachiatum was reduced to 17% and S. cepivorum did not grow. However, T. longibrachiatum maintained antagonistic activity against S. cepivorum in the presence of NaCl. Compared with uninoculated plants, inoculation with T. longibrachiatum increased the biomass of plants infected with S. cepivorum, plants treated with NaCl, and also plants treated with the combined treatment of S. cepivorum and NaCl. In plants infected with S. cepivorum and with the combined treatment of NaCl and S. cepivorum, the disease severity index was 69 and 89 %, respectively. However, inoculation with T. longibrachiatum reduced the disease severity index to 12 and 60 % in plants infected with S. cepivorum and in the combined treatment of S. cepivorum and NaCl, respectively. Chlorophyll and carotenoid content were maintained in plants inoculated with T. longibrachiatum and then subjected to salinity and infection; T. longibrachiatum decreased electrolyte leakage caused by salinity and infection. In conclusion, inoculation of onion plants with T. longibrachiatum reduced damage caused by infection with S. cepivorum and NaCl in onion plants; this was achieved by maintaining biomass and the content of photosynthetic pigments and by reducing electrolyte leakage. T. longibrachiatum is a fungus with potential as a biological control agent of S. cepivorum on onion plants under salt stress.

The effectiveness of melanin from the fungi Sclerotium cepivorum, Aspergillus niger, and Albifimbria verrucaria for use in dye-sensitive solar cells (DSSCs)

Description of the subject. Novel sensitizer environmentally friendly natural pigments with suitable colors for dye-sensitive solar cells (DSSCs) are required. Here, melanized structures to obtain pigments formed by Aspergillus niger, Sclerotium cepivorum, and Albifimbria verrucaria, were used. Objectives. The goal of this study was to build DSSC solar cells to study the operation of these extracted melanins from these fungi. Method. Melanin extraction from fungal structures was carried out using KOH-HCl and NaOH-HCl and applied in the DSSC. Results. The melanin from A. verrucaria had the best fill factor (FF) (0.718), followed by that from S. cepivorum and A. niger (0.708 and 0.525). Sclerotium cepivorum melanin had the highest effectiveness (0.320%), followed by A. verrucaria (0.160%) and A. niger (0.149%). Conclusions. The I-V and V-P curves in the evaluation tests showed that fungal melanin behaved as a semiconductor; as a result, the development of DSSC-type solar cell devices employing extracts from different sources of fungal melanin appears promising.

Evaluation of Sulfur-Based Biostimulants for the Germination of Sclerotium cepivorum Sclerotia and Their Interaction with Soil.

White rot is an economically significant disease of Allium crops. The pathogen Sclerotium cepivorum produces long-lived sclerotia that germinate in response to sulfur-containing compounds released from Allium roots. Diallyl disulfide (DADS) was the primary organic sulfur compound detected in the rhizosphere soil of two garlic cultivars, "California Early and Late", growing in greenhouse conditions. DADS, dimethyl trisulfide (DMTS), dimethyl disulfide (DMDS), isopropyl disulfide (IPDS), dipropyl disulfide (DPDS), diethyl disulfide (DEDS), together with garlic oil, garlic juice, garlic powder, raw onion pieces, cabbage pieces, and Chinese cabbage pieces were investigated for their activities toward germinating dormant sclerotia. Results showed that DADS and other volatile sulfur compounds could stimulate sclerotial germination, and a dose-response was observed. In addition, garlic juice, powder, raw onion, and the two cabbages could stimulate sclerotial germination. Furthermore, the laboratory soil incubation experiments demonstrated the strong interaction of organic sulfur compounds with soil.

Efficiency of different strains of Trichoderma on the control of Sclerotinia sclerotiorum, Sclerotium rolfsii and Sclerotium cepivorum

The aim of this work was to verify the efficiency of different isolates of Trichoderma spp. on the control of Sclerotinia sclerotiorum, Sclerotium rolfsii and Sclerotium cepivorum, and the influence they pose on the conidia production of Trichoderma spp. For mycelial growth, discs with inoculum of phytopathogens were placed on the center of the Petri dishes followed by the addition of two Trichoderma sp. discs on the opposite sides of the plate after 24 hours. Every 12 hours data were collected from colonies diameters and used for the analyses of Mycelial Growth Index (MGI) and Area Under the Curve of Mycelial Growth (AUCMG). The analyses were performed by a completely randomized design with two controls, a negative one without Trichoderma sp. and one with a commercial strain of Trichoderma harzianum. Spore solution for evaluation of conidia production were made by adding 10 mL of distilled water and scratching the surface of the colonies. For S. cepivorum, all Trichoderma spp. strains reduced both indexes tested. However, while for MGI S. sclerotiorum also presented some reduction on the growth rate, the total area of this fungus was not affected. Sclerotium rolfsii strains of Trichoderma sp. from Lages and Curitibanos showed an effect on the reduction of AUCMG of this fungus, although none of the Trichoderma affected the growth rate of this phytopathogen. On the presence of S. sclerotiorum and S. cepivorum, none of the Trichoderma spp. showed any difference on conidia production when compared among themselves, nonetheless we did notice that on the presence of S. cepivorum, the strain from Rio do Sul retained its reproductive ability compared to control. Results obtained from this research can demonstrate the importance of biocontrol agents against different plant pathogens since it might have a specific antagonist-pathogen relation.

Melanin Pathway Determination in Sclerotium cepivorum Berk Using Spectrophotometric Assays, Inhibition Compound, and Protein Validation

Sclerotium cepivorum Berk is the etiological agent of white rot disease that affects plants of the genus Allium. This fungus produces resistance structures called sclerotia that are formed by a rolled mycelium with a thick layer of melanin and it can remain dormant for many years in the soil. Current interest in S. cepivorum has arisen from economic losses in Allium crops in the agricultural sector. Melanin is a component that protects the sclerotia from adverse environmental conditions In many organisms, it plays an important role in the infectious process; in S. cepivorum, the pathway by which this component is synthetized is not fully described. By using infrared spectrophotometric assays applied direct to the sclerotia and a melanin extract followed by an NMR analysis and a tricyclazole melanin inhibition experiment, it allowed us to determine the dihydroxynaphthalene (DHN)-melanin pathway by which S. cepivorum performs its melanin synthesis. Moreover, we focused on studying scytalone dehydratase (SDH) as a key enzyme of the DHN-melanin synthesis. We obtained the recombinant SDH enzyme and tested its activity by a zymogram assay. Thereby, the S. cepivorum melanogenic route was established as a DHN pathway.

Stromatinia cepivora (white rot of onion and garlic)

Stromatinia cepivora (white rot of onion and garlic)

Screening of onion species against white rot disease caused by Sclerotium rolfsii Sacc. in Manipur

White rot of onion caused by Sclerotium rolfsii has devastated onion cultivations at various small scale onion growing locations in Manipur. The maximum white rot disease incidence was observed during the month of April in all the onion species and the minimum disease incidence was observed during February month. The disease symptoms were not apparent during the first three months after planting. The symptoms of white rot became evident during second week of February with yellowing of leaves starting from tips and gradually progressing downwards. The disease became most obvious during last week of March to first week of April when the basal part of onion stem starts rotting and drooping and the plant wilts and collapse. The bulbs of infected plants are decayed and accompanied by the signs of the pathogen including white mycelium and sclerotia.

Effect of some two tree extractives on Sclerotium cepivorum causing white rot in Allium spp.

The present study was undertaken to investigate the effect of using different extracts of two types of trees (Jatropha curcas seeds and Taxodium distichium cones). The solvents used were distilled water and ethanol. Determination of bioactive components of each extract was carried out using gas chromatography/ Mass Spectrometry (GC/MS) analysis. In general, ethanolic extract was the most effective on the both of linear growth, sclerotial numbers and mycelium characteristics of Sclerotium cepivorum than both of the cold or hot water extracts compared to control. Under In vitro conditions, treated with 20% of ethanol solvent showed a fungicidal effect meanwhile, fungistatic effects appeared at 5% for reduction of the mycelium growth..In the greenhouse experiments, the results indicated that onion transplants treated with ethanolic extract of taxodium and jatropha at 20% resulted in significant reduction to the disease with a significant increase in bulb yield compared with a check treatments. This report is one of few papers which using taxodium cones and jatropha seeds as antifungal substances against plant pathogens especially S. cepivorum under worldwide and Egypt conditions.

Crops that decrease the survival rate of sclerotia of <i>Sclerotium cepivorum</i> Berkeley in their root systems and attenuate the progress of white rot disease

Crops that decrease the survival rate of sclerotia of <i>Sclerotium cepivorum</i> Berkeley in their root systems and attenuate the progress of white rot disease

Suppression of Sclerotium cepivorum Using Biofumigation By Glucosinolate-Containing Plant and Cyanogenic Bacteria اخماد فطر الاسکيرولشيم سيبوفورم باستخدام التبخير الحيوي بالنباتات المحتوية على الجلوکوسينولات والبکتيريا المنتجة لسيانيد الهيدروجين

In dual culture antagonism test, six of eight cyanogenic bacteria were able to reduce the growth of Sclerotium cepivorum. The strains Glocoacetobacter diazotrophicus and Paenibacillus. polymyxa GQ375783.1were the most effective bacteria that recorded the highest inhibition of S. cepivorum mycelial growth by 75% and 70% respectively. Based on HCN production, two strains recorded complete inhibition of fungal growth. Moreover, the ground tissues of the nasturtium plant were able to inhibit the mycelium growth of S. cepivorum by 100%. Results of the greenhouse experiment emphasized that white-rot incidence percentage recorded the lowest values in onion cultivated in soil amended with nasturtium plant and inoculated with G. diazotrophicus plus P. polymyxa GQ375783.1. This treatment recorded the highest values of onion vegetative growth and their yield. Under field conditions, the soil treated with investigated two methods of biofumigation led to suppress white rot disease by the rate of 100% while using each one individually, it reduced disease by the rate of 94.4 and 94.9 % respectively. All onion treatments that inoculated with cyanogenic bacteria showed higher records of DH and N2-ase activity than uninoculated ones. The highest values DH and N2-ase were recorded with soil amended with nasturtium and inoculated with cyanogenic bacterial strains. Additionally, the same treatment gave the highest values of peroxidase and polyphenoloxidase activity, onion NPK content, and the plant's vegetative growth as well as their yield. Therefore, the biofumigation using nasturtium and investigated bacterial strains can be recommended in controlling White-rot disease in onions and increasing their productivity.

In-vitro Assessment of Fungicides and pH Levels on the Mycelial Growth and Sclerotia Production of Sclerotium rolfsii Sacc. causing White Rot of Onion in Manipur

Seven fungicides and five different pH levels were evaluated against Sclerotium rolfsii Saccardo, causing white rot of onion in Manipur. The efficacies of the fungicides were evaluated by poisoned food technique on potato dextrose agar. The effect of different pH levels was evaluated on potato dextrose broth by measuring dry mycelial weight and counting the number of sclerotia produced by the fungus. Three fungicides, namely, Hexaconazole (500 and 1000ppm), Propiconazole (500 and 1000ppm) and Mancozeb (1000 and 2000ppm), resulted 100% inhibition of mycelial growth and sclerotia production of the white rot pathogen. The mycelial growth and sclerotia production of S. rolfsii were minimal in pH 4.0, providing a total of 0.62g of dry mycelial weight and 1069 sclerotia. The maximum mycelial growth of 0.76g was recorded at pH 5.0, followed by 0.72g at pH 6.0. Maximum number of sclerotia were produced at pH 7.0, followed by pH 6.6. and 6.0 successively.