Changes In Fungal Populations Research Articles

Erratum to: Resistance of wheat pathogen Zymoseptoria tritici to DMI and QoI fungicides in the Nordic-Baltic region - a status

Septoria tritici blotch (STB) caused by the ascomycete Zymoseptoria tritici (Z. tritici) is currently the most prevalent foliar disease in wheat in the Nordic-Baltic region. Fungicide availability in this region differs greatly and is generally more limited than in other European regions. Monitoring of fungicide sensitivity is an essential tool to survey changes in fungal populations in order to react and be able to adapt recommendations for fungicide use. In this study the authors give an overview of the current situation of 14α-demethylation inhibitor (DMI) and quinone outside inhibitor (QoI) sensitivity of Z. tritici from Scandinavia and the Baltic countries. A total of 985 isolates from the Nordic-Baltic region were investigated for EC50 of DMI epoxiconazole and prothioconazole. Fungicide sensitivity remains at a high level with values ranging from 0.07 to 0.48 mg L−1 for epoxiconazole and 1.17 to 9.47 mg L−1 for prothioconazole. Point mutation I381V in the DMI target gene CYP51 was dominant throughout the region, but mutations D134G, V136A/C and S524T were also detected in the population in 2014. Screening for inserts in the CYP51 promoter region revealed that a ~ 1000 bp insert is predominant in the entire region. Only a single isolate was found in Denmark, harbouring the 120 bp insert, known to reduce fungicide sensitivity. Two Danish isolates which had elevated resistance levels were associated with an enhanced efflux. Significant differences were found across the area for the presence of G143A, conferring QoI resistance. As there is only limited access to results from this area, these findings can serve as reference for future fungicide sensitivity investigations and for evaluation of changes in the Northern European Z. tritici population.

PCR-DGGE Analysis of the Fungal Community of Red-pepper Fields Utilizing Eco-friendly Farming Methods

In this study, we analyzed the changes in fungal populations of red-pepper fields employing eco-friendly farming methods, such as microbial agents and crop rotation, by using polymerase chain reactions coupled with denaturing gradient gel electrophoresis (PCR-DGGE). Primer specific for fungi were used to determine the contribution of domains to the microbial community. Analysis of planted and non-planted soil samples applying PCR-DGGE technology offered evaluation of long-term patterns in fungal species richness. To evaluate the stability of DGGE patterns from different soils, comparison of planted and non-planted soil samples were compared using PCR-DGGE. The number of DNA fragments obtained from all planted soil samples by DGGE separation was far greater (14 to 15 bands) than that of the non-planted soil samples (3 to 4 bands). In addition, 14 bands were observed from crop continuation soil treated with agrochemicals and 18 bands from crop rotation soil treated with microbial agents. The PCR-DGGE analysis suggests that the use of crop rotation and microbial agents benefits the fungal community more than crop continuation using agrochemicals. These results indicate that crop rotation with microbial agents was better able to support beneficial organisms, enable more effective biological control and maintain a healthier balance of nutrients, organic matter and microorganisms.

Rumen bacterial, archaeal, and fungal diversity of dairy cows in response to ingestion of lauric or myristic acid1

The objective of this experiment, part of a larger study, was to investigate changes in rumen bacterial, archaeal, and fungal diversity in cows fed medium-chain saturated fatty acids. In the main study, 6 lactating dairy cows were dosed intraruminally with 240 g/(cow · d) of stearic (SA, control), lauric (LA), or myristic (MA) acid in a replicated 3 × 3 Latin square design trial. Experimental periods were 28 d, and cows were transfaunated between periods. Lauric acid decreased protozoal counts in the rumen by 96% compared with SA and MA (compared with SA, MA had no effect on ruminal protozoa). Whole ruminal contents samples were collected 2, 4, 6, 8, 10, 14, 18, and 24 h after the morning feeding on d 23 of each experimental period, stored frozen, and later composited by cow and period for microbial profile analyses, which involved tag-encoded flexible (FLX) amplicon pyrosequencing to provide diversity analyses of gastrointestinal bacterial, archaeal, and fungal populations of the cattle. The LA treatment, either directly or through its effect on protozoa, had a profound effect on the microbial ecology of the rumen. Ruminal populations of Prevotella, Bacteroides, and Enterorhabdus were decreased (P = 0.04 to P < 0.001) by more than 2-fold in LA treatments compared with SA, and Clostridium populations were decreased (P = 0.01) in LA- compared with MA-treated cows. The proportion of Ruminococcus was not affected by treatment, although the LA treatment had the least proportion of Ruminococcus. Proportions of Eubacterium, Butyrivibrio, Olsenella, and Lactobacillus genera were increased (P = 0.03 to 0.01) by LA compared with MA or SA. The LA treatment, possibly through its effect on protozoa physically associated with archaea, resulted in an increase (P = 0.01) in the archaeal methanogenic genus Methanosphaera and a decrease (P = 0.01) in Methanobrevibacter. Few changes in fungal populations caused by treatment were detected. Collectively, results indicate that LA, either through antiprotozoal or direct antimicrobial effects, altered bacterial and archaeal populations in the rumen of dairy cows, but effects on fungal populations were not clear.

Effects of dry sugar cane yeast on the diet intake, digestibility and bovine rumen microbial populations

The objective of this research was to evaluate the effect of the dry sugar cane yeast (DSCY) protein addition on the intake, digestibility and rumen microbial population (bacteria, protozoa, and fungi) in zebu steers fed cotton seed processing residue (CSPR). Six Nellore steers, with rumen and duodenal cannulae were used. Data were analyzed according to a randomized block design, each one with three treatments: 0.0, 4.0 and 8.0% of DSCY as a percentage of supplied dietary dry matter. Parameters evaluated were: intake, digestibility and ruminal protozoa populations. In addition, the most probable numbers of rumen fungal and bacteria populations were estimated. The DM, OM, EE, NDF and ADF intakes and digestibilities were not influenced by different levels of DSCY, possibly because of the high value of the nitrogen C fraction of the CSPR (44.5% DM). Low levels of undegradable protein fraction from yeast did not provide an expected optimized synchronization energy/nitrogen in order to enhance the degradation rate. The presence of 4.0% DSCY in the diet significantly reduced fungal rumen population. There were no significant changes in fungal populations between the 4.0% and the 8.0% treatments. However, bacterial populations showed an increase when submitted to 8.0% DSCY compared to 4.0% in the diet. Protozoal populations did not vary significantly among the treatments. It was concluded that supplementation of DSCY to zebu steers did not affect the intake, digestibility and microbiological rumen populations.

Development of a European system for identification of emerging mycotoxins in wheat supply chains

This paper describes the results of a research project aimed at the conceptual development of an identification system for emerging mycotoxins in European feed and food supply chains of wheat. Basic requirements for such a system were addressed, including the selection of indicators, locating information sources, development of underlying model, and investigation of stakeholders' needs. The selection and ranking of key indicators for identifying emerging mycotoxins was based on a literature review, followed by a structured expert judgment study. The expert study was based on the Delphi technique and used a panel of 43 European experts. The Delphi procedure resulted in a selected set of 12 key indicators for each of three relevant stages of the wheat chain (cultivation; transport and storage; processing). For wheat cultivation, these were: relative humidity/rainfall, crop rotation, temperature, tillage practice, water activity in the kernels, crop variety, harvest conditions, changes in fungal populations, fungicide use, plant health, regional infection pressure and food safety awareness. For the majority of the selected indicators, information sources were identified in specific European countries. However, most sources are not readily accessible and particular data is lacking. A theoretical concept for a model underlying the envisioned emerging mycotoxin identification system has been developed. The model links the key indicators and their information sources to aid and promote identification of emerging mycotoxins. It manages different types of information sources and levels of available information. The needs of various stakeholder groups regarding the system were investigated by means of two empirical elicitation sessions. The results showed that all stakeholders considered that such a system would be beneficial. One major challenge expected in establishing the system is stakeholder commitment to sharing data and information. This requires great efforts in improving communication and interaction between the key stakeholders.

Changes in bacterial and fungal biomass C, bacterial and fungal biovolume and ergosterol content after drying, remoistening and incubation of different layers of cool temperate forest soils

Changes in bacterial and fungal biomass C, bacterial and fungal biovolume, ergosterol content, basal respiration and metabolic quotient ( qCO 2) after air-drying, rewetting and incubation (6 h and 2, 10 and 40 days) of four soil layers (L, F, H, a h) of an aspen ( Populus tremuloides Michx.) forest and the F/H layer of a pine ( Pinus contorta Loud.) forest in the Canadian Rocky Mountains were studied. Bacterial and fungal biomass were determined by selective inhibition of substrate-induced respiration (SIR) by streptomycin and cycloheximide. Bacterial and fungal biovolume were determined by epifluorescence microscopy using acridine orange and calcofluor white M2R for staining of bacteria and fungi, respectively. SIR inhibition was optimized by testing a wide range of inhibitor concentrations and different substrates.In general, air-drying (20°C, 14 days) caused only slight reductions (< 10%) in microbial biomass (SIR) in each of the layers. The effect of air-drying on bacteria and fungi depended on the soil materials. In general, most of the measurements indicated little changes in bacterial and fungal populations after air-dried layers had been rewetted. Basal respiration was increased strongly in each of the rewetted layers and C metabolized during the burst in respiration may have originated from killed microorganisms in aspen L, F and H, but other C resources presumably were also made available by air-drying of aspen a h and pine F/H.During incubation of rewetted layers bacterial biomass and biovolume increased for 10 days in most of the layers, resulting in a decrease in the fungal-to-bacterial ratio. Then, between days 10 and 40 fungi became more dominant in most of the layers and the fungal-to-bacterial ratio increased.Each of the indices measured to determine changes in bacterial and fungal populations were correlated significantly. The correlation between SIR inhibition by cycloheximide and ergosterol content was particularly high ( r 2 = 0.83) and an overall mean of 11 mg ergosterol g − fungal biomass C was obtained, indicating that changes in fungal populations in forest layers can be monitored accurately by measuring ergosterol contents. The usefulness of each of the methods used to characterize changes in bacterial and fungal populations in soil is discussed.

Use of ergosterol, diaminopimelic acid and glucosamine contents of soils to monitor changes in microbial populations

Ergosterol, diaminopimelic acid (DAP) and glucosamine contents were measured in stored (−50 kPa, 25°C), air-dried and substrate-amended (glucose, 1 % w/w) grassland and arable soils. Amounts ranged from 0.2 to 13.9 μg ergosterol. 12 to 311 μg DAP and 420 to 2070 μg glucosamine g −1 soil. The grassland soils had higher amounts of each compound than the arable soil. Generally, storage and air-drying reduced, whilst substrate-amendment increased, amounts of ergosterol and DAP in soil. Changes in amounts of glucosamine were not consistent between soils. Comparison with previously determined biomass contents from these same soil treatments gave ratios of ergosterol-to-mycelial C of 0.002–0.059, DAP-to-bacterial C of 0.3–2.6 and glucosamine-to-biomass C ratios of 2.2–6.7. Ergosterol was linearly correlated with fungal surface area in a common function for two of the soils (0.16 μg ergosterol cm −2 fungi) and DAP with bacterial surface area in each soil (1.6 μg DAP cm −2 bacteria), suggesting that ergosterol and DAP were specific to fungal and bacterial populations respectively. The novel finding that the ergosterol contents of these soils could be accounted for by the amount of fungi present, suggests that soil ergosterol content is a sensitive indicator of changes in fungal populations.

Responses of microbial components of the rhizosphere to plant management strategies in a semiarid rangeland

Rhizosphere microbial responses to herbage removal and irrigation were assessed in a semi-arid rangeland by determining phosphatase and dehydrogenase activity, ATP, and fluorescein diacetate (FDA)-stained and total hyphal lengths. In four sequential one-week experiments (15 sample dates), irrigation resulted in significant decreases in dehydrogenase activity on 53% of the sample dates, while with herbage removal such decreases were only observed on only 7% of the sample dates. The combined treatment (herbage removal and irrigation) gave intermediate responses, with dehydrogenase decreasing on 33% of the dates, which indicated that herbage removal mitigated the reduction of rhizosphere microbial activiy caused by irrigation. In contrast to these decreases, total hyphal lengths increased on 47 and 33% of the dates in the combined and irrigated treatments, respectively. However, in both treatments active hyphae decreased on 47% of the dates. Comparison of dehydrogenase activity with hyphal length responses suggested that overall microbial activity, as opposed to the fungal component, was preferentially stimulated by herbage removal, while irrigation caused a decrease in both microbial activity and degradation of fungal hyphae. Increases in dehydrogenase activity were observed within 24 hr of herbage removal in 3 of 4 weeks. An increase in dehydrogenase activity was also observed upon initiation of irrigation, but dehydrogenase activity decreased with continued irrigation. These results indicated that manipulation of range plants by herbage removal and irrigation would lead to distinct changes in fungal populations and microbial activities in the rhizosphere. The relationship between plant management and rhizosphere microbial responses can be studied under field conditions to provide better understanding of plant-soil interactions with the ultimate goal of improving productivity of semiarid ecosystems.

Fungal flora of soil polluted with copper

The effects of copper pollution on the soil fungal flora was investigated. Soils treated with 100, 200, 400, 800 or 1600 μg Cu g −1 were used for experiments to study changes in fungal populations, especially the development and dominance of copper-tolerant fungi. Fungi were sampled 1, 3 and 5 months after copper treatment. All the correlation coefficients between the copper contents and the number of fungal colonies plated were positive. The higher the copper concentration in soil, the more 1000 μ Cu ml −1 tolerant fungi were isolated. The relative number of 1000 μg Cu mr −1 tolerant fungi from the soil treated with 1600 μg Cu g −1 was about 30% of those of the control 14 days after treatment. Within the limits of this experiment, the increase in fungal populations was directly correlated with the increase of dominant Cu-tolerant fungi. From control soils, containing low quantities of copper, 1000 μg Cu ml −1 tolerant fungi were also isolated; whereas, from soils containing high amounts of copper, some Cu-sensitive fungi were isolated. Most of the 1000 μg Cu ml −1 tolerant fungi were Penicillium spp. It was concluded that the genus Penicillium may be dominant in soils polluted with copper.

Changes in fungal populations during storage of Dalbergia bark

Nineteen species of fungi were isolated during a 16-week successional study on Dalbergia bark. The most common species present throughout the succession were Aspergillus nidulans and A. fumigatus. Maximum colony forming units (CFU) were recorded during the 3rd week. The highest temperature recorded during the succession was 47 °C. In culture, most of the fungi showed a wide range of temperatures for growth, i.e. 15–47 °C; some were confined to a temperature range of 15–37 °C or 15–32 °C. Most of the fungi, except Acrophialophora fusispora, could utilize cellulose. Only seven fungi showed some lignin utilizing capacity.