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1.
Ultra-violet radiation damage to Metarhizium flavoviride conidia and the protection given by vegetable and mineral oils and chemical sunscreens 总被引:3,自引:0,他引:3
D. MOORE P. D. BRIDGE P. M. HIGGINS R. P. BATEMAN C. PRIOR 《The Annals of applied biology》1993,122(3):605-616
Metarhizium flavouiride conidia formulated in oil or water were exposed to simulated solar radiation. Radiation below 320 nm killed conidia and caused delays in the germination of survivors; germination was greater after 48 h of incubation than after 24 h. UV exposure of conidia formulated in oil for 2 h reduced germination from 99% to 37.5% after incubation for 48 h. Exposure of conidia in water to UV for 1 h resulted in 4.7% germination after 24 h incubation compared with 36.5% for conidia formulated in oil. The addition of 1% oxybenzone resulted in 81.9% conidial germination after 3 h exposure and 48 h incubation compared with 28.1% in oil without the sunscreen. 相似文献
2.
Susceptibility of Larvae of Galleria mellonella to Infection by Aspergillus fumigatus is Dependent upon Stage of Conidial Germination 总被引:1,自引:0,他引:1
The ability of conidia of the human pathogenic fungus Aspergillus fumigatus to kill larvae of the insect Galleria mellonella was investigated. Conidia at different stages of the germination process displayed variations in their virulence as measured
using the Galleria infection model. Non-germinating (‘resting’) conidia were avirulent except when an inoculation density of 1 × 107 conidia per insect was used. Conidia that had been induced to commence the germination process by pre-culturing in growth
medium for 3 h were capable of killing larvae at densities of 1 × 106 and 1 × 107 per insect. An inoculation density of 1 × 105 conidia per insect remained avirulent. Conidia in the outgrowth phase of germination (characterised as the formation of a
germ tube) were the most virulent and were capable of killing 100% of larvae after 5 or 24 h when 1 × 107 or 1 × 106 conidia, that had been allowed to germinate for 24 h, were used. Examination of the response of insect haemocytes to conidia
at different stages of the germination process established that haemocytes could engulf non-germinating conidia and those
in the early stages of the germination process but that conidia, which had reached the outgrowth stages of germination were
not phagocytosed. The results presented here indicate that haemocytes of G. mellonella are capable of phagocytosing A. fumigatus conidia less than 3.0 μm in diameter but that conidia greater than this are too large to be engulfed. The virulence of A. fumigatus in G. mellonella larvae can be ascertained within 60–90 h if infection densities of 1 × 106 or 1 × 107 activated conidia (pre-incubated for 2–3 h) per insect are employed. 相似文献
3.
D. NORSE 《The Annals of applied biology》1973,74(3):297-306
The ranges over which the germination of conidia of Alternaria longipes was > 50% were 10–35 °C on agar and 15–30 °C on tobacco leaf disks. Germination was optimal at 22.5 °C; so was germ-tube growth, reaching c. 300 and 102 μm on agar and leaf disks respectively after 12 h. On average, 27% more conidia germinated and germ-tubes were 62% longer on disks from leaves washed for 5 min under running water than on disks from unwashed leaves. At controlled saturation deficits germination after 8 h at 1.1 and 2.3 mb was 42.3 and 9.3% respectively and the rate of germ-tube growth was < 0.8 μm/h, compared with 94.4% and 8.3 μm/h in standing water. These results, together with some field data, suggests that germination in the field is largely restricted to periods when free moisture is present on leaves. In Malawi, leaf temperatures and the duration of dew at night were adequate to allow germination and penetration in the absence of rain. Pollen, when applied with the inoculum, had little effect on the number of germinated conidia, but caused a c. tenfold increase in the number of successful penetrations. 相似文献
4.
W. M. Zhang K. Mckee M. Sulz T. Mykietiak X. Li D. E. Cole 《Biocontrol Science and Technology》2003,13(3):299-312
A native fungus, Plectosporium tabacinum (van Beyma) M. E. Palm, W. Gams et Nirenberg, has potential as a bioherbicide for the control of both herbicide-resistant and herbicide-susceptible false cleavers. Limited information is available on the infection process of P. tabacinum. P. tabacinum spore distribution pattern, germination, penetration, and colonization on false cleavers leaves were examined using confocal, light, and scanning electron microscopy. The results demonstrated that conidia were distributed over the entire surface of leaves and cotyledons. More than 90% of the conidia germinated on the leaf surface 6-8 h after inoculation. Penetration of the leaf epidermis by conidia started 8-10 h after inoculation. Histological observation showed that no appressoria were formed by P. tabacinum, but its hyphae produced appressed club-like structures that penetrated the cuticle and epidermal layers. No stomata or other natural openings were observed on the upper leaf surface of false cleavers seedlings. Penetration occurs directly on epidermal cells with more frequent intercellular penetrations. Hyphal penetration was visualized at a depth of 30 and 40 üm after 8 and 16 h of incubation, respectively. Secondary hyphae colonized mesophyll cells 16 h after inoculation. Even spore distribution, short spore germination time, club-like infection structure formation, direct penetration, quick colonization, and mucous secretion on false cleavers leaves may contribute to the kill of false cleavers by P. tabacinum. Slow spore germination and germ tube growth, low spore germination numbers, and no infection structure formation on Brassica napus leaves may be factors affecting the host selectivity of P. tabacinum. 相似文献
5.
Background The expression of fungal allergens is increased by the germination of conidia. We assessed the state of germination of fungal
conidia recovered by nasal lavage after environmental exposure.
Methods Nasal lavage was performed on twenty adults at three stages: the start of the experiment, after 1 h indoors, and after 1 h
outdoors. One half of the lavage liquid was immediately treated to prevent in-vitro germination and stained with periodic
acid Schiff (PAS) to enable identification of germinated and ungerminated conidia. The untreated half of the lavage liquid
was cultured on nutrient agar plates to enumerate and identify viable fungi.
Results PAS staining showed that both ungerminated and germinated conidia, and hyphal fragments, were present in the nasal cavity.
The most prevalent fungi recovered were Aspergillus, Alternaria, Cladosporium, Epicoccum, Penicillium, and Yeast species. The number of viable fungi recovered after 1 h indoors was significantly less than after 1 h outdoors
(P < 0.01).
Conclusions Viable fungi and germinating conidia, in addition to ungerminated conidia and hyphal fragments, were present in the nasal
cavity after both indoor and outdoor exposure. This provides novel insight into the pathogenicity of exposure to fungal aeroallergens. 相似文献
6.
Studies were conducted to identify oil-based formulating agents (paraffinic oil, palm oil and emulsifiable adjuvant oils (EAOs))
for Metarhizium anisopliae that were superior to water with simple surfactants using a germination test and a bioassay against Boophilus microplus. Germination of conidia in all formulations, except 10% coconut EAO, produced more than 68% germination at 24 h and nearly
100% at 48 h. Coconut oil (average survival time (AST)=4.6±0.28 days) and 10% liquid paraffin EAO (AST=4.4±0.15 days) enhanced
the pathogenicity of M. anisopliae to B. microplus relative to water (AST=8.4±0.42 days). M. anisopliae in 10% liquid paraffin EAO was the most effective formulation having a moderately high germination after 24 h and a low AST
as well as a high AST in the control. In the second experiment, germination of conidia in 2% liquid paraffin EAO and 2% Cropspray
was higher than in 2% Codacide oil at 24 h, however, all treatments reached 100% germination after 48 h. The ASTs of the EAO
based M. anisopliae formulations (Average AST=6.4±0.54 days) were similar but lower that the ASTs of the controls (Average AST=9.6±0.28 days). 相似文献
7.
Summary A diffusible self-inhibitor of germination of conidia of Glomerella cingulata appears to act as a regulator of protein synthesis. Both uptake of labeled amino acids and their incorporation into protein are reduced by the inhibitor or by crowding. Compared to conidia incubated without self-inhibitor, conidia incubated with self-inhibitor incorporated no labeled amino acids into protein in the first hour and 80% less in 6h. Thoroughly washed conidia were more permeable to amino acids and incorporated 6 times more precursor into proteins than unwashed conidia. At high density in nutrient medium, conidia of G. cingulata preferentially form secondary conidia instead of germ tubes and a mycelium. This inhibition of germination of conidia and regulation of development is mimicked by exposing them to an auto-inhibitor extracted from used culture medium and conidial washings. Germination of conidia of G. cingulata involves two steps, an initial step of 5 h duration which continues unaffected by crowing (1.7×108/ml) and a subsequent 2 h step which conidia do not take unless they are sufficiently diluted. It is this step for which protein synthesis may be required.Non-Standard Abbreviations CHM
cyloheximide
- NM
Neurospora minimal medium
- psi
pound per square inch
- RPH
reconstituted algal protein hydrolysate
- TCA
trichloroacetic acid 相似文献
8.
Chronological histological alterations of Metarhizium anisopliae during interaction with the cattle tick Boophilus microplus were investigated by light and scanning electron microscopy. M. anisopliae invades B. microplus by a process which involves adhesion of conidia to the cuticle, conidia germination, formation of appressoria and penetration
through the cuticle. Twenty-four hours post-infection conidia are adhered and germination starts on the surface of the tick.
At this time, the conidia differentiate to form appressoria exerting mechanical pressure and trigger hydrolytic enzyme secretion
leading to penetration. Massive penetration is observed 72 h post-inoculation, and after 96 h, the hyphae start to emerge
from the cuticle surface to form conidia. The intense invasion of adjacent tissues by hyphae was observed by light microscopy,
confirming the ability of M. anisopliae to produce significant morphological alterations in the cuticle, and its infective effectiveness in B. microplus. 相似文献
9.
The kinetics of the development of the mycelial form of Sporothrix schenckii from yeast cells and conidia in a minimal basal medium with glucose at pH 4.0 and 25 °C were established. Germ tube formation was used as the index of germination for both yeast cells and conidia. Yeast cells were first observed to develop germ tubes after 3 h of incubation, reaching 92±5%, after 12 h of incubation. Germ tubes were first detected in conidia after 9 h of incubation, and 12 h after inoculation 92±6% of the conidia had germ tubes. After 24 h of incubation, fully developed, sporulating mycelia were observed from both yeast cells and conidia. A delay in germ tube formation from yeast cells was observed when But2cAMP(10 mM) and But2cGMP (10 mM) were added to the medium. Also the addition of caffeine, a cyclic nucleotide phosphodiesterase inhibitor, inhibited the yeast to mycelial transition. Conidial germination into the mycelial form was also inhibited when cAMP, But2cAMP and caffeine were added to the medium. These results suggest the possible involvement of cyclic nucleotides in the control of dimorphism in S. schenckii. 相似文献
10.
Conidiation of the entomopathogenic fungus Metarhizium acridum on agar media was investigated. M. acridum CQMa102 exhibits two different conidiation patterns on agar media: normal conidiation in which conidia are formed on extended hyphae and microcycle conidiation in which conidiation occurs directly after conidia germination. Microcycle conidiation resulted in a mass of conidia produced via budding by accelerated development at the inoculation site. The mean total conidial yield (conidiation at day 10) was 4–5-fold greater after microcycle conidiation than during normal conidiation. Insect pathology assays indicated that microcycle conidia produced on SYA agar were as effective as normal aerial conidia against the locust. Ultraviolet (UV)-resistance tests showed no significant differences between the two types of cell propagules. However, microcycle conidia were more heat resistant than normal aerial conidia, and accumulated higher levels of trehalose in response to heat induction compared to normal aerial conidia. 相似文献
11.
Kunert J 《Folia microbiologica》2000,45(4):325-329
Peroxynitrite was tested for its effects on the opportunistic pathogenic fungusAspergillus fumigatus. It did not kill any dormant or swollen (4 h in a glucose-peptone medium) conidia in concentrations up to 6.25 mmol/L and
the growth of germlings (after 6 or 9 h) was only slightly inhibited by 5 mmol/L peroxynitrite. The peroxynitrite donor SIN-1
(up to 10 mmol/L, I d in buffer) did not kill any conidia but inhibited their germination and growth, depending on the medium.
Ten mmol/L SIN-1 in a poor medium was fungistatic and germination was stopped for 20 h. Nine strains ofA. fumigatus showed resistance comparable to the model strain, while 6Candida albicans strains were much more susceptible to both peroxynitrite and its donor. The results indicate that peroxynitrite does not
contribute substantially to the antifungal activity of phagocytes againstA. fumigatus. 相似文献
12.
Long-term persistence of entomopathogenic fungi as biopesticides is a major requirement for successful industrialization.
Corn oil carrier was superior in maintaining germination rates of Isaria fumosorosea SFP-198 conidia during exposure to 50°C for 2 h, when compared with other oils, such as soybean oil, cottonseed oil, paraffin
oil, and methyl oleate. The corn oil-based conidial suspension (91.6% germination) was also better in this regard than conidial
powder (28.4% germination) after 50°C for 8 h. Long-term storage stabilities of corn oil-based conidial suspension and conidial
powder at 4 and 25°C for 24 months were investigated, based on the correlation of germination rate with insecticidal activity
against greenhouse whiteflies, Trialeurodes vaporariorum. Viability of conidia in corn oil was more than 98.4% for up to 9 months of storage at 25°C, and followed by 23% at 21 months.
However, conidial powder had only 34% viability after 3 months of storage at 25°C, after which its viability rapidly decreased.
The two conidial preparations stored at 4°C had better viabilities than those at 25°C, showing the same pattern as above.
These results indicate that corn oil-based conidial suspension can be used to improve conidial persistence in long-term storage
and be further applied to the formulation of other thermo-susceptible biological control agents. 相似文献
13.
The germination of conidia of Peronospora farinosa f. sp. betae, collected from sugar beet and suspended in deionized water, was inhibited by dilution with 10% solutions of glycerol, glucose or sucrose and with sap from sugar-beet leaves. Germination was stimulated by diluting with deionized water but not with tap water or biological saline. Substances that diffused from excised buds of sugar-beet plants into deionized water also stimulated germination of conidia but diffusates from leaves did not. This may partly explain why buds are more susceptible to downy mildew than leaves in sugar beet. Germination of conidia was apparently stimulated more by diffusates from buds of seedlings than by those from buds of older plants; this may help to explain why sugar-beet seedlings are more susceptible to downy mildew than older plants. Diffusates from plants of four sugar-beet stocks, that differed from each other in susceptibility to downy mildew, had very similar effects on germination of P. farinosa conidia. Stimulation of spore germination on the surfaces of buds and leaves did not seem, therefore, to be an important factor in determining resistance or susceptibility to downy mildew in these stocks. 相似文献
14.
Conidia produced by submerged cultivation of the thermophilic fungus Thermomyces lanuginosus were superior to conidia from agar plates when used as inoculum, due to a faster and more synchronous germination. With conidia derived from submerged liquid culture at 40-45 degrees C more than 90% germination was achieved at 50 degrees C within 3 h whereas the same percentage germination was only achieved after 5 h incubation of conidia produced on agar plates. The temperature during conidial formation, and conidial age at the time of harvesting, were factors influencing germination of the conidia. 相似文献
15.
A study was conducted to determine water-assisted dissemination of conidia of Coniothyrium minitans (Cm), a mycoparasite of Sclerotinia sclerotiorum (Ss), in four soils (yellow–brown soil, red-clay soil, fluvo-aquic soil and black soil) and one sand. Conidial suspensions (1×107 conidia mL?1) of Cm were applied to sieved (2 mm screen) soil or sand in glass tubes to test vertical dissemination (VD) and in aluminum boxes to test horizontal dissemination (HD) of conidia. Results showed that conidia of Cm could be disseminated with water and spread in soil or sand for 16–20 cm vertically and for 5–10 cm horizontally. The conidial concentration of Cm was logarithmically reduced with the increase in depth of VD or the distance of HD. Dissemination of Cm conidia in sand was better than that in four soils. Potting experiments were done to further understand the potential of water-assisted dissemination of Cm conidia in suppression of Ss carpogenic germination. Results showed that more apothecia were produced by Ss sclerotia located at the soil surface than those at 5 and 10 cm in depth. The minimum Cm concentration for suppression of Ss carpogenic germination was 1000 conidia g?1 soil. Two-season field trials indicated that water-assisted application of Cm was an effective strategy used at the time for transplanting oilseed rape seedlings to suppress Ss carpogenic germination, thereby reducing the primary infection source for sclerotinia diseases of oilseed rape. 相似文献
16.
Polyanskaya L. M. Tolstikhina T. E. Kochkina G. A. Ivanushkina N. E. Zvyagintsev D. G. 《Microbiology》2004,73(4):383-388
The autoregulation of conidium germination in phytopathogenic micromycetes of the genera Fusarium, Botrytis, and Bipolaris was studied. It was shown that Trichoderma longibrachiatum was less competitive than Fusarium oxysporum after their simultaneous inoculation but inhibited the phytopathogen growth in the case of earlier introduction. In the latter case, no autoinhibition of the germination of F. oxysporum conidia occurred; moreover, a cooperative effect was observed, i.e., the number of germinated F. oxysporum conidia increased with an increase in their density. 相似文献
17.
The effect of culture age on yields, desiccation tolerance and resistance to ultraviolet radiation of Plectosporium alismatis, a potential mycoherbistat of aquatic weeds in Australian rice fields, was studied. P. alismatis was grown in a liquid basal medium supplemented with malt extract and sodium nitrate and harvested after 7, 14 or 21 days incubation. Although chlamydospore yields harvested from 14-day-old liquid cultures were significantly higher (29.2×105 chlamydospores mL?1) than chlamydospore yields harvested from 7-day-old liquid cultures (1.07×105 chlamydospores mL?1) or from 21-day-old liquid cultures, the germination of freshly-harvested chlamydospores from 7-day-old cultures (72.7%) was significantly reduced when propagules were grown for 14 days (55.3%). When exposed to UV-radiation, conidia and chlamydospores harvested from 14-day-old cultures germinated at a lower rate (<20%) than conidia and chlamydospores harvested from 7-day-old cultures (>40%). When conidia and chlamydospores were dried and subsequently exposed to UV, less than 30% of propagules harvested from 7-day-old cultures germinated, whereas less than 10% of propagules harvested from 14-day-old cultures germinated. A three-way analysis of variance including culture age, UV exposure and type of propagules confirmed that the culture age had more impact on the germination of fresh or dry propagules (P=0.00001 and P=0.0004, respectively) than the type of propagules considered (P=0.5). These results demonstrate that the culture age impacts significantly propagule yields and germination of P. alismatis conidia and chlamydospores, particularly after stress caused by dehydration and/or exposure to UV-B radiation. 相似文献
18.
F. R. S. Paixão E. R. Muniz L. P. Barreto C. C. Bernardo G. M. Mascarin C. Luz 《Biocontrol Science and Technology》2017,27(3):324-337
The thermotolerance of oil-based conidial formulations of Metarhizium anisopliae s.l. (IP 46) and Metarhizium robertsii (ARSEF 2575) were investigated. Conidia of IP 46 or ARSEF 2575 were suspended in different adjuvants and exposed to 45?±?0.2°C for 4, 6, 8 or 24?h; their viability was then assessed after 48?h incubation at 27?±?1°C. Conidia heated in pure mineral or vegetable oil exhibited mean relative viability exceeding 70% after 8?h of heat exposure, whereas low germination (≤20%) was observed when conidia were heated in water (Tween 80® 0.01%), carboxymethyl cellulose gel or emulsifiable oils (Graxol® or Assist®) and exposed to heat for 6 or 8?h. In addition, conidia of IP 46 suspended in either pure mineral or canola oil and exposed to heat for 48?h had moderate viability, 57% or 41%, respectively. Unstable oil-in-water emulsions showed a higher percentage of conidia incorporated into oil micellae, while the stable emulsions had higher percentage of conidia outside the oil micellae. The thermotolerance of conidia formulated in stable emulsions, however, did not differ from that of conidia formulated in unstable emulsions. The present study highlights possibilities to alleviate the deleterious effects of heat stress towards Metarhizium spp. conidia applied for controlling arthropod pests and vectors through oil-based formulations. 相似文献
19.
The effect of nutritional conditions on spore qualities was investigated in order to select which propagules, conidia or chlamydospores, would be most suitable for mycoherbicide development. Plectosporium alismatis was grown in a liquid basal medium supplemented with glucose and a mineral nitrogen source (sodium nitrate) or an organic nitrogen source (casamino acids). Conidial and chlamydospore yields, germination rate and shelf-life were compared. Two growth models were developed: on one hand, sodium nitrate added as the sole nitrogen source was partially utilised (8%), resulting in poor growth (1.77±0.02 mg mL?1; 6±1.7×105 conidia mL?1). Under these conditions, P. alismatis produced dense, melanised-like aggregates that contained chlamydospores (12.4±0.7×104 chlamydospores mL?1). Germination rates of chlamydospores and conidia produced under these conditions was high (80%). Twenty percent of chlamydospores were able to germinate after 4 months storage at 25°C, while survival of conidia declined rapidly (<2%). When casamino acids were added to the liquid medium as the sole nitrogen source, P. alismatis produced sparser pellets resulting in high dry weights (5.37±0.09 mg mL?1 and high conidia numbers (9.6±1.5×106 conidia mL?1), while no chlamydospore were observed. The germination rate of conidia produced in casamino acids was low (33±13%) after 8 h incubation and microcycle conidiation occurred. Five percent of these conidia germinated after 4 months storage. These data indicate that chlamydospores may be suitable for mycoherbicide development, provided further optimisation of yields is achieved. 相似文献
20.
In a series of laboratory experiments, tobacco leaf discs infested with scales of the glasshouse whitefly Trialeurodes vaporariorum, were immersed in suspensions of conidia of three strains of the entomopathogenic fungus Verticillium lecanii. The germination of conidia on the insect was recorded and compared with the germination of conidia applied to Czapek—Dox Complete Medium. Laboratory bioassays were performed to record the mortality of whitefly scales exposed to conidia of all three fungal strains. The rate of germination of conidia on the whitefly scales was much reduced compared to that oh complete medium. Differences were recorded in the rate of germination of the three strains on complete medium, but not on the whitefly scales. There was no correlation between the pathogenicity of the strains to whitefly scales in laboratory bioassays and the rate of germination on the host. 相似文献