Reduction In Fungal Biomass Research Articles

Evaluation of antifungal activity of methanolic extracts of Dicanthium annulatum for the management of Macrophomina phaseolina

The present study was carried out to assess the antifungal potential of an allelopathic grass Dicanthium annulatum (Forssk.) Stapf. against Macrophomina phaseolina (Tassi) Goid. isolated from cowpea [Vigna unguiculata (L.) Walp.] plants suffering from charcoal rot disease. Different parts of this grass namely shoot, root and inflorescence were extracted in methanol. After evaporation of methanol, different concentrations (0, 0.5, 1.0, …, 3.0 g ml-1) of the extracts were prepared and their antifungal activity was studied. In general, extracts of all the three parts exhibited antifungal activity. However, a marked variation in antifungal activity among the extracts of different parts of the test grass was observed. There was 7 to 51%, 29 to 71% and 33 to 81% reduction in fungal biomass due to different concentrations of shoot, root and inflorescence extracts of D. annulatum, respectively. Key words: Antifungal activity, charcoal rot, Dicanthium annulatum, Macrophomina phaseolina, methanolic extracts.

Antifungal activity of methanolic extracts of Sorghum halepense against Macrophomina phaseolina

Macrophomina phaseolina (Tassi) Goid., the cause of charcoal rot disease, is the major biotic factor that limits cowpea [Vigna unguiculata (L.) Walp.] productivity worldwide. The present study was designed to investigate the antifungal potential of an allelopathic grass Sorghum halepense Pers. for the management of M. phaseolina isolated from charcoal rot infected cowpea plants. In laboratory bioassays, different concentrations (0, 0.5, 1.0,…, 3.0 g/ml) of methanolic extracts of shoot, root and inflorescence of the test allelopathic grass were evaluated for their in vitro antifungal activity against M. phaseolina. Extracts of all the three parts of the grass exhibited variable antifungal activity. Shoot extract was found the most effective where all the extract concentrations significantly reduced the fungal biomass by 14 to 61% over control. Similarly, all concentrations of the root extract except 0.5% significantly suppressed the fungal biomass. Inflorescence extract exhibited the least antifungal activity where only 2% and higher concentrations showed the significant effect. There was 9 to 48% and 4 to 39% reduction in fungal biomass due to various concentrations of methanolic root and inflorescence extracts, respectively.

Antifungal activity of different extracts of Ageratum conyzoides for the management of Fusarium solani

Ageratum conyzoides L. is potential allelopathic weed very useful for its antifungal and antimicrobial activity. Being environmentally safe and friendly, it has the potential to substitute synthetic fungicides. The current study, therefore, was designed to evaluate the in vitro efficacy of aqueous methanolic and n-hexane extracts of A. conyzoides against the pathogenic fungi, Fusarium solani Mart. (Sacc.), isolated from roots of egg plant ( Solanum melongena ). The target fungus was exposed to various concentrations (2, 4 and 6% w/v) of aqueous, methanolic and n-hexane extracts of Inflorescence, leaf, stem and root. All the employed concentrations of extracts of four plant parts significantly suppressed the growth of the target fungal pathogen. The n-hexane extracts of leaf and inflorescence caused highly significant reduction of 84% in growth of F. solani followed by stem and root extracts which caused which caused 80% and 72% reduction in growth, respectively. The same pattern in growth reduction was observed in methanolic and aqueous extracts. Among the four parts of the tested weed, different concentrations of the methanolic extract of leaf were found to be highly effective in controlling target fungal species resulting in up to 78% reduction in fungal biomass over control followed by inflorescence (74% reduction), stem (63% reduction) and root (59% reduction) at highest used concentration. In case of aqueous extracts, the maximum reduction was observed in leaf extract (72%) followed by inflorescence, stem and root, respectively. Key words: Ageratum conyzoides , aqueous extract, Fusarium solani , n-hexane extract, methanolic extract.

BDM1, a phosducin‐like gene of Fusarium graminearum, is involved in virulence during infection of wheat and maize

Fusarium graminearum is a common pathogen of wheat and maize throughout the world. Despite recent advances in the elucidation of the genetic basis of virulence, significant gaps in the regulatory network underlying pathogenesis remain to be filled. In particular, little is known at the molecular level about the overlap among mechanisms of pathogenicity on maize and wheat. G-protein signalling has been implicated in pathogenesis in F. graminearum, although the underlying mechanisms are not fully understood. In this study, we investigated the involvement of a putative phosducin-like gene (BDM1) in growth, development and pathogenesis in F. graminearum. Targeted deletion of BDM1 revealed roles in sexual and asexual sporulation, germ tube development, hyphal branching and mycelial morphology. During pathogenesis, BDM1 is required for wild-type levels of colonization of maize silk tissue and stalks, but is dispensable for the colonization of kernels. The deletion of BDM1 also reduced the virulence of F. graminearum during the infection of wheat seedlings and heads, resulting in a significant reduction in fungal biomass and a delayed spread of visual symptom expression (i.e. bleaching in heads). Furthermore, BDM1 is required for wild-type levels of deoxynivalenol biosynthesis during the infection of wheat heads and maize silks. In summation, BDM1 is one of the few genes characterized to date in F. graminearum involved in virulence during infection of both maize and wheat. Thus, the functional characterization of BDM1 has established a new regulatory link between pathogenesis in maize and wheat, and provides a genetic resource through which the regulatory networks underlying virulence in F. graminearum can be further elucidated.

Microbial nitrogen dynamics in south central Chilean agricultural and forest ecosystems located on an Andisol

The natural soil N supply in volcanic soils (Andisols) can be a significant source of plant-available N for agro-ecosystems. Nevertheless, intensive farming systems in south Chile apply high fertilization rates, which lead to high production costs and involve a risk for adverse ecosystem effects. In order to achieve sustainable land management, a better understanding of the processes that govern soil N availability and loss, and their external drivers, is required. In this study, we selected a winter-cropland, a summer crop-winter fallow rotation, and a forest, used as a reference ecosystem. Gross N transformations (15N isotope dilution) and microbial community structure (phospho-lipid fatty acid analysis) in the topsoil were determined. Gross N mineralization was about ten times lower in the agro-ecosystems than in the forest, while gross nitrification was low in all sites. Gross N immobilization equalized or exceeded the gross inorganic N production in all sites. Microbial biomass was 3–5 times more abundant in the forest than in the agro-ecosystems. A positive relationship between the ratio fungi/bacteria and total microbial biomass was observed in these Andisols. We suggest that the reduction in fungal biomass induced a lower extracellular enzyme production and limited soil organic matter depolymerisation in the agro-ecosystems. We conclude that soil N cycling was unable to provide a significant N input for the croplands, but also the risk for ecosystem N losses was low, even under fallow soil conditions. Current fertilization practices appropriately anticipated the soil N cycling processes, but further research should indicate the potential of alternative land management to reduce fertilizer cost.

Inhibition Of Growth Of Fungi In Cashew And Pawpaw Fruit Juices By Aframonium melegueta And Allium sativum Extracts

A study was conducted to investigate the antifungal effect of Aframomium melegueta and Allium sativum on the growth of three fungi – Rhizopus stolonifer, Penicillium digilatum and Mucor mucido in Cashew and pawpawjuices. The application of the extracts singly showed significant (P < 0.05) reduction of fungal biomass at 3%(v/v), 4%(v/v) and 5%(v/v). A combination of 2 % (v/v) each of both spice extracts retarded better. Partition columnchromatographic analysis revealed that ethanolic fraction of the plant produced the highest level of inhibition of growth of the test fungi compared with methanolic and petroleum ether fractions. Extracts of Aframomiummelegueta and Allium sativum may be used as preservatives in the processing of fruit juices.Key words: Antifungal, investigate, biomass, cashew, pawpaw, juice, inhibition, preservatives.

Antifungal activity of methanol and n-hexane extracts of three Chenopodium species against Macrophomina phaseolina

Antifungal activity of methanol and n-hexane leaf, stem, root and inflorescence extracts (1, 2, 3 and 4% w/v) of three Chenopodium species (family Chenopodiaceae) namely Chenopodium album L., Chenopodium murale L. and Chenopodium ambrosioides L. was investigated against Macrophomina phaseolina (Tassi) G. Goid., a soil-borne fungal plant pathogen that has a broad host range and wide geographical distribution. All the extracts of the three Chenopodium species significantly suppressed the test fungal growth. However, there was marked variation among the various extract treatments. Methanol inflorescence extract of C. album exhibited highest antifungal activity resulting in up to 96% reduction in fungal biomass production. By contrast, methanol leaf extract of the same species exhibited least antifungal activity where 21–44% reduction in fungal biomass was recorded due to various employed extract concentrations. The various methanol extracts of C. murale and C. ambrosioides decreased fungal biomass by 62–90 and 50–84%, respectively. Similarly, various n-hexane extracts of C. album, C. murale and C. ambrosioides reduced fungal biomass by 60–94, 43–90 and 49–86%, respectively.

Impact of low-level atmospheric ozone-enrichment on black spot and anthracnose rot of tomato fruit

Tomato fruit ( Lycopersicon esculentum L.) were exposed to ozone concentrations between 0.005 (control) and 5.0 μmol mol −1 up to 13 days at 13 °C, prior to, or following, inoculation by Alternaria alternata or Colletotrichum coccodes (causes of black spot and anthracnose, respectively). Low-level atmospheric ozone-enrichment resulted in a modest, but statistically significant, reduction in fungal lesion development; higher concentrations of the gas resulting in greater effects. This finding implies concentration-specific impacts on fungal lesion development. A fluorescent lection assay revealed that the ozone-induced inhibition of visible lesion development was reflected in a similar reduction in fungal biomass below the fruit surface. Fungal spore production in vivo, was markedly reduced when fruit were stored in an ozone-enriched atmosphere. Higher concentrations/duration of exposure resulted in greater reduction in spore production, with considerable benefits resulting from exposure to low levels of ozone (i.e. below the 0.2 μmol mol −1 European threshold used for the protection of human health). In vitro, effects of ozone on spore germination depended on concentration and duration of exposure. Studies performed on fungi exposed to ozone on Potato Dextrose Agar at 13 °C and 95% relative humidity revealed no major effects on the growth of mycelia, implying the observed suppression of pathogen development was due in part to ozone-induced changes in fruit-pathogen interactions.

In vitro evaluation of antagonistic properties of Pseudomonas corrugata

Pseudomonas corrugata, a soil bacterium originally isolated from a temperate site of Indian Himalayan Region (IHR) is examined for its antagonistic activities against two phytopathogenic fungi, Alternaria alternata and Fusarium oxysporum. Although the bacterium did not show inhibition zones due to production of diffusible antifungal metabolites, a reduction in growth between 58% and 49% in both test fungi, A. alternata and F. oxysporum, was observed in sealed Petri plates after 120 h of incubation due to production of volatile antifungal metabolites. Reduction in biomass of A. alternata (93.8%) and F. oxysporum (76.9%) in Kings B broth was recorded after 48 h of incubation in dual culture. The antagonism was observed to be affected by growth medium, pH and temperature. The reduction in fungal biomass due to antagonism of bacteria was recorded maximum in the middle of the stationary phase after 21 h of inoculation. The production of siderophore, ammonia, lipase and chitinase in growth medium by P. corrugata were considered contributing to the antagonistic activities of the bacterium.

Effect of phenolic monomers on biomass and hydrolytic enzyme activities of an anaerobic fungus isolated from wild nil gai (Baselophus tragocamelus).

To test the anaerobic fungus, Piromyces sp. FNG5, for its tolerance to phenolic monomers released in the rumen by degradation of lignocellulosic poor-quality feeds. Effects of phenolic monomers on biomass and fibrolytic enzyme activities of a pure culture of lignocellulolytic anaerobic fungus (Piromyces sp. FNG5) isolated from faeces of wild nil gai (blue bull, Baselophus tragocamelus) were evaluated. There was a reduction in fungal biomass at 1 mm concentration of catechol with complete inhibition at 10 mm. p-Coumaric acid caused a reduction in biomass at 10 mm and no growth was observed above 20 mm concentration. The fungal isolate could tolerate up to 5 mm of ferulic acid without any reduction in biomass level, and was able to grow to some extent up to the highest level of ferulic acid tested (20 mm). Vanillic acid had no effect on biomass of the fungus even up to 50 mm level. The phenolic monomers varied in their potential to inhibit the secretion of carboxymethyl cellulase, xylanase, beta-glucosidase and acetyl esterase activities with catechol being the most inhibitory and vanillic acid being the least inhibitory. After 14 days of incubation, 38.49-65.14%p-Coumaric acid, 65.22-74.10% ferulic acid and 34.13-66.78% vanillic acid disappeared from the medium under anaerobic conditions. It is concluded that the anaerobic fungus Piromyces sp. FNG5 is tolerant to phenolic monomers and has ability to degrade them. Therefore, such anaerobic fungi may play an important role in fibre degradation in the rumen.

Effects of Neem Leaf Volatiles on Submerged Cultures of Aflatoxigenic Aspergillus parasiticus

Microbe-free compressed air was passed continuously for a 3-day test period through an enclosed system containing fresh neem leaves; the resultant emitted volatiles were passed over the surface of submerged liquid cultures of a wild-type aflatoxigenic isolate of Aspergillus parasiticus. Aflatoxin determinations for the fungal culture that received neem-derived volatiles, after a 3-day incubation period, resulted in a 90% overall reduction in aflatoxin production and a 51% reduction in fungal biomass when compared with cultures that did not receive neem volatiles. In a separate experiment but in a similarly enclosed system, volatiles from fresh neem leaves were collected on a small Tenax column and were thermally desorbed and cryogenically focused on a capillary gas chromatography column. The neem volatiles were subsequently separated and identified by gas chromatography-mass spectrometry. Sixty-eight compounds were identified by comparison of retention times and mass spectra with either authentic compounds or spectra from a computer-assisted library database of mass spectra. It was found that 10% of the total headspace volatiles were composed of C(3) to C(9) alkenals, which are toxic to aflatoxigenic Aspergillus spp., which could explain the bioactivity that resulted in reduced biomass in the neem-treated cultures.

Cytology of infection of 35S‐bean chitinase transgenic canola plants by Rhizoctonia solani: cytochemical aspects of chitin breakdown in vivo

Transgenic canola plants containing high, constitutive levels of bean endochitinase have been shown to be more resistant to infection by the soil‐borne pathogen, Rhizoctonia solani, than are wild‐type plants that lack the chimeric chitinase gene. To determine whether the resistance of the 35S‐chitinase plants to Rhizoctonia infection results from an antimicrobial activity of the bean chitinase in planta, an ultrastructural and cyto‐chemical study was performed on infected control and transgenic canola plants. Analysis of root tissues of infected wild‐type canola plants revealed that R. solani was capable of extensive tissue colonization including the xylem vessels. Pathogen ingress towards the vascular system was associated with marked host cell wall alterations such as disruption of middle lamella matrices that occurred in advance of fungal penetration. Fungal hyphae colonizing these tissues appeared metabolically active as judged by their typical morphological features and their extensive multiplication. In infected transgenic plants, however, the pattern of fungal colonization was different to that observed in wild‐type plants. Penetration of the host cuticle and epidermis was frequently observed, but fungal colonization was usually restricted to the cortex although, in a few cases, some fungal cells could be seen in xylem vessels. In all samples examined, severe hyphal alterations ranging from increased vacuolization to cell lysis were seen. Hyphae occasionally seen in xylem vessels were markedly damaged and often reduced to convoluted wall fragments. Cytochemical labeling of chitin using the WGA/ovomucoid‐gold complex showed that hyphal alterations correlated with extensive chitin degradation. Thus, reduction in fungal biomass, increase in hyphal alterations leading to fungal lysis and chitin breakdown appear to be typical features observed in transgenic canola plants. Because these features were not seen in infected wild‐type plants, it is likely that constitutive expression of the bean endochitinase gene is, at least in part, responsible for the enhanced protection against fungal attack observed in these plants. It is not known, however, if other components of the host defense response contribute to the resistance phenotype.

Stable successional patterns of aquatic hyphomycetes on leaves decaying in a summer cool stream

The colonization of leaf litter (Alnus glutinosa) by aquatic hyphomycetes was studied in a summer cool stream of the French Pyrenees. In spite of the rapid decomposition of leaves, the fungal community exhibited a characteristic successional pattern with three phases. The initial colonization stage was defined by a dense sporulation of the five species Tetrachaetum elegans, Lemonniera aquatica, L. centrosphaera, L. terrestris, and in particular Flagellospora curvula. After four weeks of colonization, a mature community had established. It was characterized by high species diversity and peak fungal biomass, which was measured as ergosterol content, and coincided with about 50% loss in leaf mass. With leaf decay progressing further, diversity diminished concomitant with a slight reduction in fungal biomass and a sharp decrease in the rate of conidial production. Typical species of this late successional stage were Clavatospora longibrachinata, Heliscella stellata and Goniopila monticola. This successional pattern proved to be stable both within the period of leaf fall in one year and between two successive years. Between-seasons differences were quite small as well, the striking lack of species replacement apparently being due to not exceeding the threshold temperature of 16–18 °C as previously defined in literature. In spite of this general stability in community structure, correspondence analysis discriminated the communities on leaf packs with equal exposure times according to season, with the cyclical arrangement of leaf packs on the principal factorial plane reflecting the seasonal cycle. The colonization of fresh (non-dried) leaf litter by aquatic hyphomycetes was delayed compared to air-dried litter; however, the lead diminished with progressing leaf decay, resulting in nearly identical communities on fresh and dried leaves after four weeks of decomposition.

Changes in soil microflora in response to repeated applications of some pesticides

The effects of pesticides on soil microflora were studied on arable soils that had received repeated applications of carbofuran and carbosulfan (insecticides), iprodione and vinclozolin (fungicides), and MCPA, simazine and paraquat (herbicides). Carbofuran at single and 5-fold treatments did not show any detectable detrimental effects on soil microbial biomass, but single application of carbosulfan produced a significant biomass reduction. There were dramatic reductions in soil microbial biomass following vinclozolin application, and this was due to a reduction in fungal biomass; iprodione showed less obvious biomass trends. MCPA and simazine caused no detectable effects to the microflora, but repeated paraquat application significantly lowered soil microbial biomass (chiefly fungal biomass). The results indicate that there may be substantially different effects on soil biomass produced by single or repeated applications of pesticides.