Academic literature on the topic 'C. minitans'

Coniothyrium minitans, marketed as Contans, has become a standard management tool against Sclerotinia sclerotiorum in a variety of crops, including winter lettuce. However, it has been ineffective against lettuce drop caused by S. minor. The interactions between C. minitans and S minor were investigated to determine the most susceptible stage in culture to attack by C. minitans, and to determine its consistency on S minor isolates belonging to four major mycelial compatibility groups (MCGs). Four isolates of S. minor MCG 1 and 5 each from MCGs 2 and 3 and one from MCG 4 were treated in culture at purely mycelial, a few immature sclerotial, and fully mature sclerotial phases with a conidial suspension of C. minitans. Sclerotia from all treatments were harvested after 4 weeks, air dried, weighed, and plated on potato dextrose agar for recovery of C. minitans. S. minor formed the fewest sclerotia in plates that received C. minitans at the mycelial stage; C. minitans was recovered from nearly all sclerotia from this treatment and sclerotial mortality was total. However, the response of MCGs was inconsistent and variable. Field experiments to determine the efficacy of C. minitans relative to the registered fungicide, Endura, on lettuce drop incidence and soil inoculum dynamics were conducted from 2006 to 2009. All Contans treatments had significantly lower numbers of sclerotia than Endura and unsprayed control treatments, and drop incidence was as low as in Endura-treated plots (P > 0.05). Although the lower levels of lettuce drop in Contans treatments were correlated with significantly lower levels of sclerotia, the lower levels of lettuce drop, despite the presence of higher inoculum in the Endura treatment, was attributable to the prevention of infection by S. minor. A useful approach to sustained lettuce drop management is to employ Contans to lower the number of sclerotia in soil and to apply Endura to prevent S. minor infection within a cropping season.

Sclerotinia blight, caused by Sclerotinia minor, is an important disease of peanut in North Carolina. The effectiveness of Coniothyrium minitans, a mycoparasite of sclerotia of Sclerotinia spp., was studied in a 5-year field experiment and in eight short-term experiments in northeastern North Carolina. The 5-year experiment was initiated in November 1999 to evaluate the effectiveness of repeated soil applications of C. minitans (commercial formulation, Contans WG) at 2 and 4 kg ha-1 in reducing Sclerotinia blight. In addition, individual commercial peanut fields were selected in 2001 and 2002 to evaluate a single application of C. minitans at 4 kg ha-1. No differences were found between the 2 and 4 kg ha-1 rates of C. minitans in reducing Sclerotinia blight. In 2002, there was less disease in plots receiving applications of C. minitans for either 1 or 3 years compared with the nontreated control; whereas, in 2003, C. minitans applications for 1, 2, or 3 years reduced disease and the number of sclerotia isolated from soil. A single application of C. minitans reduced sclerotia in only two of the eight short-term experiments. The integration of consecutive years of soil applications of C. minitans at 2 kg ha-1 with moderately resistant cultivars and fungicide applications may aid in the management of Sclerotinia blight in peanut.

All pesticides used in United Kingdom glasshouse lettuce production (six fungicides, four insecticides, and one herbicide) were evaluated for their effects on Coniothyrium minitans mycelial growth and spore germination in vitro agar plate tests. Only the fungicides had a significant effect with all three strains of C. minitans tested, being highly sensitive to iprodione (50% effective concentration [EC50] 7 to 18 μg a.i. ml-1), moderately sensitive to thiram (EC50 52 to 106 μg a.i. ml-1), but less sensitive to the remaining fungicides (EC50 over 200 μg a.i. ml-1). Subsequently, all pesticides were assessed for their effect on the ability of C. minitans applied as a solid substrate inoculum to infect sclerotia of Sclerotinia sclerotiorum in soil tray tests. Despite weekly applications of pesticides at twice their recommended concentrations, C. minitans survived in the soil and infected sclerotia equally in all pesticide-treated and untreated control soil trays. This demonstrated the importance of assessing pesticide compatibility in environmentally relevant tests. Based on these results, solid substrate inoculum of a standard and an iprodione-tolerant strain of C. minitans were applied individually to S. sclerotiorum-infested soil in a glasshouse before planting lettuce crops. The effect of a single spray application of iprodione on disease control in the C. minitans treatments was assessed. Disease caused by S. sclerotiorum was significantly reduced by C. minitans and was enhanced by a single application of iprodione, regardless of whether the biocontrol agent was iprodione-tolerant. In a second experiment, disease control achieved by a combination of C. minitans and a single application of iprodione was shown to be equivalent to that of prophylactic sprays with iprodione every 2 weeks. The fungicide did not affect the ability of C. minitans to spread into plots where only the fungicide was applied and to infect sclerotia. These results indicate that integrated control of S. sclerotiorum with soil applications of C. minitans and reduced foliar iprodione applications was feasible, did not require a fungicide tolerant isolate, and that suppression of Sclerotinia disease by C. minitans under existing chemical control regimes has credence.

The effects of soil temperature and moisture, and nine pesticides commonly used in peanut production, on the mycoparasitic activity of Coniothyrium minitans on sclerotia of Sclerotinia minor were evaluated. In vitro mycelial growth and conidia germination of C. minitans were sensitive to azoxystrobin, chlorothalonil, fluazinam, pyraclostrobin, tebuconazole, and diclosulam. C. minitans survived and infected sclerotia of S. minor in the presence of azoxystrobin, chlorothalonil, diclosulam, fluazinam, flumioxazin, S-metolachlor, pendimethalin, pyraclostrobin, and tebuconazole. Mycoparasitic activity was reduced by all pesticides except S-metolachlor compared with the nontreated control. Optimum conditions for infection of sclerotia were temperatures from 14 to 22°C and soil moisture from -0.33 to -1 kPa × 102. Mycoparasitic activity of C. minitans remained high (98% sclerotia infected) at temperatures ranging from 14 to 22°C, but decreased at temperatures above 28°C. Viability of sclerotia was inversely related to the proportion infected by C. minitans (r = -0.9963, P = 0.001). Mycoparasitic activity also declined when soil moisture was greater than -1 kPa × 102 or less than -0.10 kPa × 102. These results indicate that C. minitans should not be applied when temperatures exceed 28°C, during extremes in soil moisture, or when there is a high risk of contact with pesticides before it becomes established in the soil.

Survival of the sclerotial parasite Coniothyrium minitans in soil when applied as spore suspension or colonised solid substrate (maizemealperlite) inocula and ability to infect Sclerotinia sclerotiorum sclerotia incorporated into the soil after different times was assessed over 6 months Unambiguous detection of the C minitans isolate from the indigenous C minitans soil population was achieved using a hygromycin B resistant transformant (T3) which was similar in behaviour to the wild type LU112 Coniothyrium minitans was recovered from soil by dilution plating at all assessment times with higher recovery from spore suspension compared with maizemealperlite amended soil Coniothyrium minitans was able to infect and reduce viability of sclerotia incorporated into the amended soil over the 6 month experiment with spore suspension significantly increasing infection compared with maizemealperlite inoculum Hygromycin B amendment of the agar significantly increased C minitans recovery from sclerotia especially when the population of secondary fungal colonisers was high

The effect of Coniothyrium minitans on Sclerotinia sclerotiorum and Ciborinia camelliae sclerotial viability was determined on three different substrates sand soil and sawdust using fully factorial repeat experiments (Trials 1 and 2) In Trial 1 C minitans significantly reduced the number of viable S sclerotiorum sclerotia in sand (48) and sawdust (0) but not in soil (60) compared with the untreated sclerotia (92 64 and 88 respectively) after 8 weeks Although C minitans had no effect on C camelliae sclerotial viability the sawdust only treatment reduced viability to 0 after 4 weeks In the repeat experiment (Trial 2) C minitans had no effect on S sclerotiorum or C camelliae sclerotial viability although C camelliae sclerotial viability was again significantly reduced in the sawdust control treatment (812) compared with the sand and soil control treatments (>84) Coniothyrium minitans has some potential for biocontrol of S sclerotiorum but not of C camelliae Sawdust may be an option for use as an under plant mulch for control of C camelliae

The effect of the fungal mycoparasite Coniothyrium minitans applied as a spray to crops infected with Sclerotinia sclerotiorum (causal agent of white mold) on contamination of soil with S. sclerotiorum sclerotia was studied in a 5-year field experiment. Sclerotial survival also was monitored during two subsequent years, when the field was returned to commercial agriculture. In a randomized block design, factorial combinations of four crops and three treatments were repeated 10 times. Potato (Solanum tuberosum), bean (Phaseolus vulgaris), carrot (Daucus carota), and chicory (Cichorium intybus), which are all susceptible to S. sclerotiorum, were grown in rotation. Plots were treated with C. minitans or Trichoderma spp. or were nontreated (control). Crops were rotated in each plot, but treatments were applied to the same plot every year. After 3 years during which it showed no effect on sclerotial survival, the Trichoderma spp. treatment was replaced by a single spray with C. minitans during the fourth and fifth years of the trial. The effect of treatments was monitored in subsequent seasons by counting apothecia as a measure of surviving S. sclerotiorum sclerotia and scoring disease incidence. Trichoderma spp. did not suppress S. sclerotiorum, but C. minitans infected at least 90% of S. sclerotiorum sclerotia on treated crops by the end of the each season. C. minitans lowered the number of apothecia compared with the other treatments during the second year after the bean crop. C. minitans reduced the number of apothecia by ≈90% when compared with the control and Trichoderma spp. treatments and reduced disease incidence in the bean crop by 50% during the fifth year of the trial, resulting in a slightly higher yield. In 1993, but not 1994, a single spray with C. minitans was nearly as effective at reducing apothecia as three sprays (monitored in 1995). The final population size of sclerotia in soil at the end of the 7-year period was lower in all C. minitans plots than at the beginning of the trial, even in plots where two highly susceptible bean crops were grown during the period. The results indicate that the mycoparasite C. minitans has the potential to keep contamination of soil with sclerotia low in crop rotations with a high number of crops susceptible to S. sclerotiorum.

Transmission electron microscopy revealed that hyphae of the hyperparasite Coniothyrium minitans invade sclerotia of Sclerotinia sclerotiorum, resulting in the destruction and disintegration of the sclerotium tissues. The dark-pigmented rind tissue is more resistant to invasion by the hyperparasite than the unpigmented cortical and medullary tissues. Evidence from cell wall etching at the penetration site suggests that chemical activity is required for hyphae of C. minitans to penetrate the thick, melanized rind walls. The medullary tissue infected by C. minitans shows signs of plasmolysis, aggregation, and vacuolization of cytoplasm and dissolution of the cell walls. While most of the hyphal cells of C. minitans in the infected sclerotium tissue are normal, some younger hyphal cells in the rind tissue were lysed and devoid of normal contents.

Coniothyrium minitans A69 has been shown to have biological control activity against the plant pathogen Sclerotinia sclerotiorum and a PCR based assay has been developed to specifically identify this isolate The practical application of this PCR assay for detection of C minitans from soil was assessed Sterile and nonsterile soil was inoculated with spores from C minitans A69 at five different concentrations and DNA recovered using a SDS/Phenol/Chloroform method A number of factors affected DNA recovery and subsequent PCR with a maximum sensitivity of down to 1x102 spores/g soil achieved in sterile soil Detection of C minitans in nonsterile soil was hampered by failure of the fungus to germinate However this method has improved throughput and cost effectiveness compared with conventional detection methods involving quantitative colony recovery

ABSTRACT Understanding signaling pathways that modulate conidiation of mitosporic fungi is of both practical and theoretical importance. The enzymatic origin of nitric oxide (NO) and its roles in conidiation by the sclerotial parasite Coniothyrium minitans were investigated. The activity of a nitric oxide synthase-like (NOS-like) enzyme was detected in C. minitans as evidenced by the conversion of l-arginine to l-citrulline. Guanylate cyclase (GC) activity was also detected indirectly in C. minitans with the GC-specific inhibitor 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ), which significantly reduced production of cyclic GMP (cGMP). The dynamics of NOS activity were closely mirrored by the cGMP levels during pycnidial development, with the highest levels of both occurring at the pycnidial initiation stage of C. minitans. Furthermore, the NO donor, sodium nitroprusside (SNP), stimulated the accumulation of cGMP almost instantly in mycelium during the hyphal growth stage. When the activity of NOS or GC was inhibited with Nω-nitro-l-arginine or ODQ, conidial production of C. minitans was suppressed or completely eliminated; however, the suppression of conidiation by ODQ could be reversed by exogenous cGMP. The results also showed that conidiation of an l-arginine auxotroph could be restored by the NO donor SNP, but not by cGMP. Thus, NO-mediated conidiation has more than one signal pathway, including the cGMP signal pathway and another yet-unknown pathway, and both are essential for conidiation in C. minitans.

In this paper, a feed-forward back-propagation artificial neural network (BP-ANN) and analysis of variance (ANOVA) are applied to a hot metal extrusion process, establishing a black box model as well as analyzing the effects of relevant process parameters on required forging load, under different operating conditions. Some finite element simulation data on extruding ck-45 steel, adopted from a published research paper, were used to train the neural model employing Levenberg-Marquardt learning algorithm. Die angle (15°–75°), friction coefficient between billet-die material pair (0.4–0.8), punch velocity (168–203 mm/s), and billet temperature (1000°C–1260°C) were selected as the inputs, while the extrusion load (tone) was considered as the network’s output. Based on the results during modeling attempts, a 4-10-10-1 size neural network has been decided on as the appropriate architecture of the process model. Testing predictive accuracy of the developed model was also done using a new data set (8 data samples), which has not been used in the training phase. The comparative errors with respect to the desired FEM simulations are all in acceptable ranges (less than 12%) thereby the network’s generalization capabilities were confirmed. Having established the appropriate neural model, analysis of variance (ANOVA) technique was then applied to the original training data base to find and recognize the level of importance of each parameters and their possible dual interactions on the extrusion loading force within 95% of confidence interval (α = 0.05). Based on the obtained inferences, the best optimal combination of parametric settings which leads to the minimum required extruding load was then revealed and recommended. The optimally minimized extrusion force was then predicted by the trained network model. Neural network tool box (NNET) of the Matlab software and design of experiments module of Minitab software were employed as platforms to develop neural simulations and ANOVA technique, respectively. The overall results indicate the feasibility and effectiveness of the proposed approach in a real manufacturing environment and eliminate the need to carry out expensive as well as time consuming trial and error experimentations to reach to the optimum operating conditions.

The objectives of the project were: a) to construct the site-specific integrative expression cassettes carrying: (i) the chiA gene for a 58-kDa endochitinase, (ii) the pyrrolnitrin biosynthesis operon, and (iii) the acdS gene encoding ACC deaminase; b) to employ these constructs to engineer stable recombinant strains with an expanded repertoire of beneficial activities; c) to evaluate the rhizosphere competence and antifungal activity of the WT and modified strains against pathogenic fungi under laboratory and greenhouse conditions; and d) to monitor the persistence and impact of the introduced strains on culturable and nonculturable rhizosphere microbial populations in the greenhouse and the field. The research generally support our concepts that combining strategically selected genes conferring diverse modes of action against plant pathogens into one organism can improve the efficacy of biological control agents. We hypothesized that biocontrol agents (BCAs) engineered to expand their repertoire of beneficial activities will more effectively control soilborne plant pathogens. In this work, we demonstrated that biocontrol activity of Pseudomonas fluorescens Q8r1-96 and Q2-87, both producing the antibiotic 2,4-diacetylphloroglucinol (2,4-DAPG) effective against the plant pathogenic fungus Rhizoctonia solani, can be improved significantly by introducing and expressing either the 1.6-kb gene chiA, encoding the 58-kDa endochitinase ChiA from the rhizosphere strain SerratiaplymuthicaIC1270, or the 5.8-kb prnABCDoperon encoding the broad-range antibiotic pyrrolnitrin (Prn) from another rhizosphere strain, P. fluorescens Pf-5. The PₜₐcchiAandPₜₐcprnABCDcassettes were cloned into the integrative pBK-miniTn7-ΩGm plasmid, and inserted into the genomic DNA of the recipient bacteria. Recombinant derivatives of strains Q8r1-96 and Q2-87 expressing the PₜₐcchiA or PₜₐcprnABCD cassettes produced endochitinase ChiA, or Prn, respectively, in addition to 2,4-DAPG, and the recombinants gave significantly better biocontrol of R. solani on beans under greenhouse conditions. The disease reduction index increased in comparison to the parental strains Q8r1-96 and Q2-87 to 17.5 and 39.0% from 3.2 and 12.4%, respectively, in the case of derivatives carrying the PₜₐcchiAcassette and to 63.1 and 70% vs. 2.8 and 12,4%, respectively, in the case of derivatives carrying the PₜₐcprnABCDcassette. The genetically modified strains exhibited persistence and non-target effects comparable to those of the parental strains in greenhouse soil. Three integrative cassettes carrying the acdS gene encoding ACC deaminase cloned under the control of different promoters were constructed and tested for enhancement of plant growth promotion by biocontrol strains of P. fluorescens and S. plymuthica. The integrative cassettes constructed in this work are already being used as a simple and efficient tool to improve biocontrol activity of various PGPR bacteria against fungi containing chitin in the cell walls or highly sensitive to Prn. Some parts of the work (e. g., construction of integrative cassettes) was collaborative while other parts e.g., (enzyme and antibiotic activity analyses) were fully synergistic. The US partners isolated and provided to the Israeli collaborators the original biocontrol strains P. fluorescens strains Q8r1-96 and Q2-87 and their mutants deficient in 2,4-DAPG production, which were used to evaluate the relative importance of introduction of Prn, chitinase or ACC deaminase genes for improvement of the biocontrol activity of the parental strains. The recombinant strains obtained at HUJI were supplied to the US collaborators for further analysis.