Aspergillus lacticoffeatus was found on coffee beans in venezuela and indonesia, and is an effective producer of ochratoxin a. Sclerotium cepivorum is the causal agent of the disease commonly known as allium root rot. It is the teleomorph of sclerotium cepivorum, the cause of white rot in onions, garlic, and leeks. The sugar fraction was the most stimulatory, whereas, the amino acid fraction was not effective. Some movement of sulphorhodamine into sclerotia of rhizoctonia solani kuhn, which have no rind, occurred but the fluorochrome was arrested after permeation of at most the outer five layers of cells. Sclerotium cepivorum is the asexual reproductive form of stromatinia cepivora and is a plant pathogen, causing white rot in allium species, particularly onions, leeks, and garlic. One role of sclerotia is to survive environmental extremes. Data are presented on the antagonistic effects of the fungi isolated from sclerotia ofsclerotium cepivorum and from nonrhizosphere soil taken from around the roots of infected onions upon mycelial growth and sclerotial germination ofs. Mass production of sclerotium cepivorum the sclerotia of s. In some higher fungi such as ergot, sclerotia become detached and remain dormant until favorable growth conditions return. Four fungal species were recorded in vitro as potential mycoparasites of sclerotia of sclerotium cepivorum, the causal agent of onion white rot. Read differential stimulation of germination of sclerotia of sclerotium cepivorum by cultivars of onion and its effect on white rot disease, plant pathology on deepdyve, the largest online rental service for scholarly research with thousands of academic publications available at your fingertips. To gain some understanding of the antagonism process histological and enzymatic studies of antagonism within infected onion roots were undertaken as well as ecological studies. The dormancy of sclerotia from axenic cultures broke down after storage in soil for 12 weeks.
Sclerotia of sclerotium cepivorum formed on onion bulbs in soil were shown to undergo a period of constitutive dormancy lasting months during which they failed to respond maximally to the germination stimulant diallyl disulphide. One biological alternative to this problem is to select novel strains of trichoderma with different mechanisms of action against these plant pathogens to ensure efficient control. At the time this study commenced trichoderma koningii strains had reduced incidence of sclerotium. Aspects of the biology of the sclerotia of sclerotium cepivorum. Sclerotia definition of sclerotia by the free dictionary. Unlimited viewing of the articlechapter pdf and any associated supplements and figures. Essential oil chemical composition and antifungal effects. As the disease progresses, sclerotia are formed and eventually released into the soil. Ultrastructure of antagonism of sclerotium cepivorum by. It is a problem found all over the world on allium spp. Stimulation of sclerotial germination of sclerotium. This is the easiest method to case the grains and fruit them as is. Wastes from crop processing should never be returned to the field. Wetsieving floatation technique for isolation of sclerotia.
Look for symptoms from midsummer until early autumn. The emerging bean, ontario bean producers marketing board, summer issue 1988, 1820. Vertical distribution of sclerotia of sclerotium cepivorum and host root systems relative to white rot of onion and garlic f. Parasitised sclerotia appeared shrunken and decayed and failed to germinate. Detection of sclerotium cepivorum within onion plants. Symptoms garlic plants in the field with yellowing and dying leaves from stromatina cepivorum, the causal agent of garlic white rot. In most isolates, sclerotia produced under sterile and unsterile conditions showed a constitutive dormancy immediately after maturing. Strategies for management of sclerotium cepivorum berk. Whenever possible, fields where alliums have previously been grown should be. Sclerotia of the fungus may be disseminated by wind, and wind erosion should be avoided by appropriate wind breaks. Sclerotia killed by autoclaving were poorly colonized.
Stem rot of garlic allium sativum caused by sclerotium. Potential of biofumigation for control of diseases caused. Phylogenetic placement of plant pathogenic sclerotium. The stimulatory effects of the different fractions of onion extract on sclerotial germination ofsclerotium cepivorum were studied. Pdf efficacy of germination stimulants of sclerotia of. Aspergillus piperis was isolated from black ground pepper and produces large yellow to pink brown. The in vitro response of two sclerotinia minor, five s.
Flooding for eradication of the onion and garlic white rot. Large sclerotia of sclerotium cepivorum sciencedirect. A wetsieving floatation technique that facilitates the rapid isolation of forceps, surface sterilized in 0. Effect of temperature and soil water potential on degradation of s. It is found on various species of allium, causing rot fig. Sclerotium definition of sclerotium by the free dictionary. It is a common disease worldwide and can cause severe crop losses jkdams 1981. Aspergillus costaricaensis was isolated from soil in costa rica and produces large pink to greyish brown sclerotia. The pathogen survives in the soil as sclerotia, which are. Soil temperature and moisture effects on sclerotium. Pdf selective sclerotium cepivorum growth agar media and other. Extract from onion bulbs and diffusate from roots of onion seedlings were fractionated by column chromatography. Jan 29, 2019 the effect of soilapplied allium crop products on the stromatinia cepivora viability and the incidence of white rot in subsequent onion and garlic crops were evaluated in this work. Sclerotium cepivorum and host root systems relative to white.
In the first set of experiments testing the effect of different soil water potentials on degradation of s. Sclerotia are, th erefore, a vulnerable part of the lifecycle and disease control measures are being targeted towards them. Sclerotinia sclerotiorum and sclerotium cepivorum are soil pathogens which have generated resistance to synthetic fungicides. Studies of the biology of sclerotium cepivorum berk. Development of sclerotium rolfsii sclerotia on soybean, corn, and wheat straw, under different soil temperatures and moisture contents. A simple and rapid laboratory test was developed to trigger sclerotial germination under unsterile conditions. Antifungal activity and resistance induction against. Wetsieving floatation technique for isolation of sclerotia of sclerotium cepivorum from muck soil.
Garlic powder as a source of germination stimulants in the management of inoculum of sclerotium cepivorum, the onion and garlic white rot fungus a preliminary report central oregon agricultural research center 1993 annual report. Management of allium white rot sclerotium cepivorum in onions on organic. A split plot experimental design was used, with a factorial arrangement. Abstract sclerotium cepivorum the causal agent of white rot of onions persists in soil in the form of sclerotia whose germination is triggered by volatile sulphides. The biology, ecology, and control of sclerotium rolfsii. The fungus was first studied by halsted and later by many others.
Download fulltext pdf virulence and host range of sclerotium rolfsii and s. Control of allium white rot sclerotium cepivorum with. The survival of sclerotia of sclerotinia trifoliorum erikss. In the present research was determined the antagonism effect. This is a soil borne fungus and affects susceptible crops planted in infected soil. The biocontrol potential of three native costa rican trichoderma asperellum strains has been evaluated against the necrotrophic ascomycete sclerotium cepivorum, the causal agent of onion allium cepa l. Since the pathogen doesnt have functional spores, a small, round, seedlike structure known as sclerotia. White rot is a serious disease of the alliums, especially bulb onions, garlic and leeks, caused by the soilborne fungus sclerotium cepivorum which can persist in the soil for many years. Some effects of diallyl bisulphide on sclerotia of sclerotium. In costa rica, where climatic conditions enhance the development of this pathogen, white rot reduces onion yields up to 50% of total harvest. Sclerotinia sclerotiorum and sclerotium cepivorum, recovered at two to three monthly intervals postburial december 2011. New ochratoxin a or sclerotium producing species in. Effect of potassium bicarbonate on fungal growth and. Stromatinia cepivora is a fungus in the division ascomycota.
Pdf in vitro sensitivity of two species of sclerotinia. In contrast to this, the sclerotia of some isolates germinated quite well as soon as they were mature. The initial symptoms of the disease were typical watersoaked spots, which progressed to rotting, wilting, blighting, and eventually death. Hall formerly graduate research assistant, and extension plant pathologist, respectively, department of plant pathology, university of california, davis 95616. Antifungal activity against sclerotium cepivorum berk. Gs 83, trichoderma asperellum skt1, fusarium equiseti gf183 and penicillium simplicissmum gp172. Effects of cultivation, conditioning and isolate on.
The results indicate that other factors are more important in the suppressive effect of composted onion waste on s. However, this crop is affected by white rot, caused by the fungus sclerotium cepivorum berk, which spreads rapidly and causes significant crop losses pinto et al. The basis of this host specificity involves the response of the sclerotia. Garlic powder as a source of germination stimulants in the. For their evaluation, a comparison was made of the number of days to sclerotia production dps, number of sclerotia formed ns and the diameter of the colony dc at 2, 4, 6, 8, 10, 12, and 14 d after planting. Botrytis produces treelike conidiophores amongst mycelium which bear spores. Control of these diseases is very difficult because they produce sclerotia that can survive in the soil for many years. Percent survival of laboratoryproduced sclerotia of sclerotium cepivorum, treated with three biological control agents and recovered at two to three monthly intervals postburial december 2011. Virulence and host range of sclerotium rolfsii and s. Apoplastic permeability of sclerotia of sclerotium rolfsii. A sclerotium sklrom, plural sclerotia sklro, is a compact mass of hardened fungal mycelium containing food reserves. Stewart botany department, university of auckland, auckland, new zealand sclerotia of sclerotium cepiuorum much larger than typical infective sclerotia were common on naturally infected onions at pukekohe, new zealand, during one season but were rare in the next. Eighty percent of the bacterial antagonists isolated from soil samples and sclerotia of s.
It was described and named by saccardo from speci mens communicated by stevens. However aspergillus niger sensu stricto has not been reported to produce sclerotia, and is thought to be a purely asexual organism. Sclerotium rolfsii sclerotium cepivorum and rhizoctonia solani by nicola young and anne e. On a worldwide basis, white rot is probably the most serious threat to allium crop production of any disease. The potential of using agronomic practices for reducing the survival of sclerotia of sclerotium cepivorum in the field and hence protecting onions from white rot, a disease caused by this pathogen was investigated. The influence of the inoculation with plant growthpromoting fungi pgpf isolates on growth enhancement of onion plants and progress of white rot disease in onions, caused by sclerotium cepivorum, was evaluated. Stem rot disease was found in garlic allium sativum l. Fungi isolated from sclerotia of sclerotium cepivorum and.
Effect of environmental factors and sclerotium cepivorum. Essential oil chemical composition and antifungal effects on sclerotium cepivorum of thymus capitatus l. The buildup and spread of white rot to uninfested areas is a serious concern, as white rot can render a field unusable for garlic or other allium species for as long as 40 years, even without an allium host. Pdf strategies for management of sclerotium cepivorum berk. Most of the isolated fungi especiallypenicillium species were antagonistic to mycelial growth. The results demonstrate the potential use of composted onion waste as a method for white rot control, and as a means of disposing of packhouse onion wastes. Potential for reducing survival of sclerotia of sclerotium. Culture filtrates and organic solvent extracts of sclerotium cepivorum liquid cultures were evaluated for their antifungal activities against the same fungus. Even after the breakdown of constitutive dormancy sclerotia were subject to exogenous dormancy from which they were only released by the presence of species.
Studies of dormancy in sclerotia of sclerotium cepivorum. Schematic representation of biologically induced resistance triggered by pathogen infection red arrow, insect herbivory blue arrow, and colonization of. Sclerotium cepivorum is a major disease of allium crops worldwide. It is the most destructive fungal disease of garlic. Trichoderma asperellum biocontrol activity and induction. A comprehensive sclerotia cultivation guidefrom spore print. Isolation and identification of fungi associated to sclerotia of sclerotium cepivorum, causal agent of white rot in onion, in the highlands of cartago, costa rica. Under greenhouse conditions, soilartificially infested with sclerotia of s. The infective sclerotia remain viable in the soil for many years and are stimulated to germinate by the presence of a susceptible crop. Here we report, for the first time, the production of sclerotia by certain strains of aspergillus niger when grown on cya agar with raisins, or on other fruits or on rice. Ashford school of biological science, the university of new south wales, nsw 2052, australia received 20 march 1995.
Bacteria antagonistic to the fungal pathogen sclerotium cepivorum berk. Reduction of stromatinia cepivora inocula and control of white rot. Additional studies on the chemical control of onion white. Efficacy of germination stimulants of sclerotia of sclerotium cepivorum for management of white rot of garlic. Download pdf 8 mb abstract the fungus, sclerotium cepivorum berk. Allium white rot, biological control, sclerotium cepivorum, tebuconazole, trichoderma spp. Pdf white rot sclerotium cepivorum berk an aggressive pest of. Introduction mexico at the end of 2010 had 19,225 ha cultivated with onion allium cepa l. Various methods of application of the fungicide procymidone were evaluated for the control of onion white rot sclerotium cepivorum berk. Mycelium can grow from one plant to a nearby plant.
The ability of pgpf isolates to inhibit the growth and germination of the sclerotia of s. A comprehensive sclerotia cultivation guide from spore. The germination of sclerotia was reduced after soaking in culture filtrates of pgpf. Journal of pure and applied microbiology, august 2014. Values on far right represent aupss values of untransformed data. Pdf essential oil chemical composition and antifungal. Sclerotium cepivorum, selective media, onion extract, sclerotia, ph degree. Differential stimulation of germination of sclerotia of. Independent data points at time zero represent % germination prior to burial table a. Sclerotium cepivorum survives in soil as sclerotia, which can remain viable in the soil for a substantial. In vitro antagonist action of trichoderma strains against. The tested products were onion powder, garlic powder, onion oil, garlic oil and allium waste onion and garlic that are described as sclerotial germination stimulants. Mycoparasitism of sclerotia of sclerotinia and sclerotium.
Sclerotia of sclerotium cepivorum were attacked by the mycoparasite more slowly than those of s. In all cases, low permeability depended on an intact outer layer, and when sclerotia of each species were bisected to provide direct access of. Selection of fungal bcas of sclerotium cepivorum for. Both sclerotinia minor the cause of sclerotinia lettuce drop, sld and sclerotium cepivorum the cause of allium white rot, awr are economically important soilborne diseases. Fungal growth mycelium of botrytis is grey in color while that of sclerotium is creamwhite. Filtrates at 50% taken from 30 to 45dayold cultures have reduced s. Different letters denote significant differences at p0. Under field conditions, sclerotial germination stimulants were.
In moist sand, steamed soil, and natural soil the mycoparasite infected and destroyed more than 95% of the amended 1% ww sclerotia of s. The global pest, white rot, sclerotium cepivorum berk is one of the serious. Diallyldisulphide to reduce the numbers of sclerotia of sclerotium. Light and scanning electron microscopy revealed colonisation of the internal structure of the sclerotium by the mycoparasites. Flooding for eradication of the onion and garlic white rot fungus, sclerotium cepivorum, from infested field soil central oregon agricultural research center 1992 annual report seriesreport number. Antifungal activity and resistance induction against sclerotium. Even after the breakdown of constitutive dormancy sclerotia were subject to exogenous dormancy from which they were only released by the presence of species of. Mycoparasitism of sclerotia of sclerotium cepivorum. Formation of sclerotia and production of indoloterpenes by. The pathogen is an imperfect fungus with strong taxonomic links to the sclerofiniaceae.
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