Inhibition Of Sclerotium Formation Research Articles

Design, Synthesis, and Antimicrobial Activity of Quindoline Derivatives Inspired by the Cryptolepine Alkaloid.

Based on the structural characteristics of the cryptolepine alkaloid, a series of new quindoline derivatives bearing various substituents were prepared and evaluated for their fungicidal and antibacterial activities. Bioassay results showed that compound D7 displayed superior in vitro fungicidal activities against Sclerotinia sclerotiorum, Botrytis cinerea, Fusarium graminearum, and Rhizoctonia solani with EC50 values of 0.780, 3.62, 1.59, and 2.85 μg/mL, respectively. Compound A7 showed apparent antibacterial activities toward Xanthomonas oryzae pv. oryzae with a minimum inhibitory concentration (MIC) value of 3.12 μg/mL. Significantly, in vivo antifungal activity suggested that the curative effect (98.3%) of compound D7 was comparable to that of the positive control azoxystrobin (96.7%) at 100 μg/mL. Preliminary mechanistic studies showed that compound D7 might cause mycelial abnormality of S. sclerotiorum, cell membrane breakage, accumulation of reactive oxygen species (ROS), and inhibition of sclerotia formation. Therefore, compound D7 could be a novel broad-spectrum fungicidal candidate against plant fungal diseases.

Design, synthesis and biological evaluation of novel evodiamine and rutaecarpine derivatives against phytopathogenic fungi

Evodiamine and rutaecarpine are two alkaloids isolated from traditional Chinese herbal medicine Evodia rutaecarpa, which have been reported to have various biological activities in past decades. To explore the potential applications for evodiamine and rutaecarpine alkaloids and their derivatives, various kinds of evodiamine and rutaecarpine derivatives were designed and synthesized. Their antifungal profile against six phytopathogenic fungi Rhizoctonia solani, Botrytis cinerea, Fusarium graminearum, Fusarium oxysporum, Sclerotinia sclerotiorum, and Magnaporthe oryzae were evaluated for the first time. Furthermore, a series of modified imidazole derivatives of rutaecarpine were synthesized to investigate the structure-activity relationship. The results of antifungal activities in vitro showed that imidazole derivative of rutaecarpine A1 exhibited broad-spectrum inhibitory activities against R. solani, B. cinerea, F. oxysporum, S. sclerotiorum, M. oryzae and F. graminearum with EC50 values of 1.97, 5.97, 12.72, 2.87 and 16.58 μg/mL, respectively. Preliminary mechanistic studies showed that compound A1 might cause mycelial abnormalities of S. sclerotiorum, mitochondrial distortion and swelling, and inhibition of sclerotia formation and germination. Moreover, the curative effects of compound A1 were 94.7%, 81.5%, 80.8%, 65.0% at 400, 200, 100, 50 μg/mL in vivo experiments, which was far more effective than the positive control azoxystrobin. Significantly, no phytotoxicity of compound A1 on oilseed rape leaves was observed obviously even at a high concentration of 400 μg/mL. Therefore, compound A1 is expected to be a novel leading structure for the development of new antifungal agents.

Some Plants Showing Antagonism to Five Plant Pathogenic Fungi

Fungi are among the main agents of plant diseases, being responsible for major losses in agriculture. The control of these microorganisms carried out using chemical compounds and numerous cases of resistance have already been observed, which makes it necessary to search for alternative methods of management of these pathogens. Therefore, the aim of this study, to evaluate the antifungal potential in plants. Twenty-four (24) plant extracts were tested for their antifungal potential against five plant pathogenic fungi: Sclerotinia sclerotiorum (Ss), Stromatinia cepivora (Sc), Fusarium oxysporum (Fox), Colletotrichum gloesporioides (Cg) and Verticillium dahlia (Vd). For the evaluation of the fungicidal potential, plant extracts were prepared by liquefying the plants in distilled water. The extracts were incorporated into PDA (Potato-Dextrose-Agar) culture medium to a final concentration of 35% and autoclaved. Then, PDA discs colonized by the aforementioned fungi were added to the center of each plate with the respective treatments (plant extracts). When all control treatments (PDA medium without plant extract) had colonized the entire Petri dish, the diameters of the fungal colonies were measured to calculate the Mycelial Growth Inhibition Index (MGI). Tests showed that all these plant extracts have some antifungal activity, ranging from 0 to 100% inhibition. In general, extracts of basil, lavender, guaco, rue, toxic cassava and black plum were the ones that stood out, with MGIs above 50%. New studies are being conducted to evaluate the activity of plant extracts without autoclaving, inhibition of sclerotia formation, to determine the minimum inhibitory concentration, as well as other parts of plants like roots and seeds, mixtures of plant extracts and in vivo antagonism tests.

Design, Synthesis, and Antifungal Evaluation of 8-Hydroxyquinoline Metal Complexes against Phytopathogenic Fungi.

Phytopathogenic fungal infections have become a major threat to agricultural production, food security, and human health globally, and novel antifungal agents with simple chemical scaffolds and high efficiency are needed. In this study, we designed and synthesized 38 8-hydroxyquinoline metal complexes and evaluated their antifungal activities. The results showed that most of the tested compounds possessed remarkable in vitro antifungal activity. Especially, compound 1e exhibited the highest antifungal potency among all target compounds, with EC50 values of 0.0940, 0.125, 2.95, and 5.96 μg/mL, respectively, against Sclerotinia sclerotiorum, Botrytis cinerea, Fusarium graminearum, and Magnaporthe oryzae. Preliminary mechanistic studies had shown that compound 1e might cause mycelial abnormalities of S. sclerotiorum, cell membrane permeability changes, leakage of cell contents, and inhibition of sclerotia formation and germination. Moreover, the results of in vivo antifungal activity of compound 1e against S. sclerotiorum showed that 1e possessed higher curative effects than that of the positive control azoxystrobin. Therefore, compound 1e is expected to be a novel leading structure for the development of new antifungal agents.

In-vitro bioefficacy of fungal antagonists against root rot of Pea caused by Rhizoctonia solani (Kuhn)

In-vitro effectiveness of various antagonistic fungi namely Aspergillus niger, A. flavus, Trichoderma koningii, T. atroviride, and T. harzianum were evaluated against Rhizoctonia solani by dual culture technique on potato dextrose agar. According to the observation recorded after 5 days, all the treatments were found to be superior over control (R. solani), but among all treatments A. niger was found to the most effective antagonist, with highest radial growth inhibition of the pathogen (77.01 percent), followed by A. flavus, T. harzianum and T. koningii i.e., 66.23, 64.42 and 62.20 percent. While as, T. atroviride was found to be the least effective one with minimum growth inhibition i.e., 42.21 percent. Whereas, at the same time control (R. solani) showed 100 percent radial growth and covered the whole Petri Plate within 5 days. All the bio-control agents were significantly effective to inhibit the sclerotia formation and development, except T. atroviride in which formation of sclerotia was recorded, while in all other treatments complete inhibition of sclerotia formation was recorded after 10 days of incubation.

Silicon induces resistance to postharvest rot of carrot caused by Sclerotinia sclerotiorum and the possible of defense mechanisms

The inhibitory potential of silicon (Si) against Sclerotinia sclerotiorum, the causal agent of postharvest carrot rot was investigated under in vitro and in vivo conditions, and possible modes of action were evaluated. Silicon at the concentration of 10 mM strongly decreased the mycelial growth of S. sclerotiorum by 92.2% with inhibition of sclerotia formation by 76.3%. Myceliogenic and carpogenic germination of S. sclerotiorum sclerotia were inhibited by 89.1 and 78.9%, respectively, at the same concentration. The minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) values were 12 and 30 mM, respectively. Cell membrane permeability and lipid peroxidation of S. sclerotiorum mycelia were increased with Si treatment. Silicon at 10 mM significantly decrease the content of oxalic acid in S. sclerotiorum mycelia compared to the control. Application of silicon at 10 mM reduced the incidence of sclerotinia rot in carrot roots by 60.6% with 40 mm lesion length. Silicon treatment enhanced the activities of peroxidase (POD), polyphenoloxidase (PPO) and phenylalanine ammonia-lyase (PAL) in carrot roots inoculated with S. sclerotiorum. These results confirm that silicon might applied as an alternative tool to chemical fungicides for controlling sclerotinia rot of carrot during storage and to promote the defense response in carrot.

Impact of Antioxidants and Micronutrients as Fungicides Alternatives in Improvment the Antagonism of Trichoderma spp. Against Sclerotinia sclerotiorum

S. sclerotiorum is a strong and resting soil pathogen with high resistance to synthetic fungicides. The biocontrol agent Trichoderma spp.alone provides moderate control of this fungus. In present study, Potassium tartrate, ascorbic acid, folic acid, thiamine and micronutrients mixture were used to improve the number of spores, fresh and dry weights, crude extracts, volatile compounds, and secondary metabolites produced by four isolates of Trichoderma against pathogen. A onetime amendment of thiamine (0.1%) or micronutrients mixture improves the antagonism efficacy of the most Trichoderma isolates showing complete prevention of pathogen growth and inhibition of sclerotia formation.

The SRAP based molecular diversity related to antifungal and antioxidant bioactive constituents for biocontrol potentials of Trichoderma against Sclerotium rolfsii Scc.

The study was performed to examine 11 isolates of Trichoderma for their bio-control potentials against Sclerotium rolfsii Sacc. causing stem rot in groundnut. The antagonists Trichoderma were subjected to sequence related amplified polymorphism (SRAP) based molecular diversity analysis and compared with their hardness to S. rolfsii with respect to secretary antifungal and antioxidant profile. T. virens NBAII Tvs 12 evident highest (87.91%) growth inhibition of test pathogen followed by T. koningii MTCC 796 (67.03%) at 7days after inoculation (DAI). Microscopic study confirmed biocontrol mechanism as mycoparasitism for Tvs 12 and antibiosis for MTCC 796. The growth inhibition of test pathogen was significantly negatively correlated with sclerotia formation and lipid peroxidation during antagonism due to release of secretary bioactive antioxidants by antagonists to terminate oxidative burst generated by S. rolfsii and causing inhibition of sclerotium formation. The GC-MS profile identified antifungal and antioxidant constituents hexadecane, 1,2-benzenedicarboxylic acid, mono (2-ethylhexyl) ester, 1-hexadecanesulfonyl chloride, and octadecane in potent antagonists Tvs 12; and nonacosane and octadecane in MTCC 796 along with two novel compounds 1-pentadecene and 1-heneicosyl formate for biocontrol activity. Molecular diversity of Trichoderma isolates associated with antagonistic activity was assessed by SRAP markers. The 115 primer combinations generate total 1328 amplified products of which, 1095 are shared polymorphic and 199 are unique polymorphic. The 15 SRAP combinations produced 18 bands to diagnose best antagonist Tvs 12 and 13 SRAP combinations generated 19 unique bands for identification of MTCC 796. The mycoparasitic antagonist Tvs 12 would be the best antagonist and released unique antifungal and antioxidant constituents to combat pathogen infection. The SRAP based genetic diversity indicates Tvs12 strain clustered with T. viride NBAII Tv23 and shared only 52% similarity with other isolates of Trichoderma. The SRAP similarities explained substantial diversity (19-68%) across Trichoderma isolates.

New Strategy for Managing Damping-off and Root Rot Disease of Cucumber Caused by Rhizoctonia solani by Seed Soaking in Formula of Antioxidant with Micronutrients

of R. solani can be remain viable in soil for several years as important source of primary infection, In our laboratory trails, The soaking of R. solani sclerotia in Potassium tartarate as antioxidant and a mixture of micronutrients for 48 h showed a great reduction in colony diameter reach to 52% with complete inhibition of sclerotia formation after 24 d of incubation. For more investigation, the treated sclerotia examined under SEM which showed germ hyphae alterations, includes, changes in measurements of hyphae, increased branches, reduce length of branches, retardation of the plasmolemma and collapse of cytoplasm. By application of this formula in greenhouse, the seedling stands up increased by 46.4% on day 6 and 60.9% respectively on day 14 over check ones. In addition to seedlings protection, treatments also improve plant height, fresh weight of shoot and root with clear increase in total phenol contents. In field experiment highest fruit production as well as increase in nitrogen, phosphor, potassium and protein content of fruits. This information sheds new light on environmental factors that influence plant-pathogen interactions, and may be applied to develop a management strategy for R. solani control based on host nutrition.

In vitro screening for the identification of potential biocontrol agents of Allium white rot

A multi-test in vitro system was designed to identify antagonistic micro-organisms of the Allium white rot (AWR) pathogen, Sclerotium cepivorum. Micro-organisms (215) comprising 140 fungi, 58 bacteria and 17 actinomycetes were isolated from AWR soils, pathogen sclerotia and diseased host tissue. Fungi were screened and scored for volatile and non-volatile antibiotic activity, inhibition of sclerotium formation, and overgrowth of colonies of S. cepivorum on agar plates. Bacteria and actinomycetes were screened for antibiotic activity only. Comparisons with known antagonists of plant pathogens were also made. The screens enabled selection of antagonists to be made based on either a ‘total score’ from all tests or on a potential mode of action basis in selected tests. Statistical analysis of total score identified inhibition of sclerotia formation and position of sclerotia formation in dual culture as the most discriminating variates in the screen.

Inhibition of sclerotium formation of Sclerotium rolfsii by compounds related to phenylthiourea

The addition of nonpolar groups to thiourea enhanced the ability of compounds to inhibit growth and sclerotium formation of Sclerotium rolfsii. At comparable concentrations, oxygen analogues (urea derivatives) did not inhibit growth or sclerotium formation.

Inhibition of sclerotium formation by Sclerotinia sclerotiorum with fluorophenylalanine

Addition of fluorophenylalanine to liquid glucose-sodium nitrate medium affected growth and sclerotium formation of Sclerotinia sclerotiorum . One isolate failed to complete the maturation step in sclerotium formation and has maintained this feature after repeated subculture.

The effect of amino acids on sclerotium formation of Rhizoctonia solani kuehn(AG-1). II. Developmental process of sclerotium and its inhibition with several amino acids.

The morphological process of sclerotium formation could be divided into 5 phases. The inhibitive effect of amino acids such as cysteine, methionine and histidine on each developmental phase was studied. The lateral branching was quite limited with the amino acids. While the aggregation of hypha was not affected. The turning from hypha to sclerotia was completely inhibited, however, this from the initials was lightly inhibited though sclerotia formed were very small. The turning from the initials only occurred at short preculturing on PDA medium. The development of whitish immatured sclerotium to pigmented matured sclerotium was also limited. The inhibition of sclerotium formation by some amino acids could be explained with the reduction of interweaving hypha caused by the inhibition of lateral branching and the limitation of cell enlargement at sclerotial maturation.

6-Methylpurine-induced inhibition of sclerotia morphogenesis in Sclerotium rolfsii and its reversal by adenosine

In liquid synthetic medium inoculated with Sclerotium rolfsii (SR), addition of 6-methylpurine (MP, 50microgram/ml) immediately after inoculation led to approximately 100% reduction in sclerotia production. Adenosine, and to a lesser extent guanosine, each at final concentration of 100microgram/ml significantly reduced inhibition of sclerotia formation by SR in presence of 50microgram/ml MP. Uridine and cytidine each at 100microgram/ml had no such effect. The inhibition of sclerotia morphogenesis could be prevented by addition of 800microgram/ml of adenosine together with 50microgram/ml MP. Reversal by adenosine of MP-induced inhibition of sclerotia development was concentration dependent.