Tissue Structure Changes of Aquilaria sinensis Xylem after Fungus Induction

In this study, we analyzed the mechanism and the process of fungal-induced agarwood formation in Aquilaria sinensis and studied the functional changes in the xylem structure after the process. The microscopic structure of the white zone, transition zone, agarwood zone, and decay zone of 12-and 18-months of inoculation A. sinensis xylem was studied. The distribution of nuclei, starch grains, soluble sugars, sesquiterpenes, fungal propagules, and mycelium in xylem tissues was investigated by histochemical analysis. The results show that the process of agarwood formation was accompanied by apoptosis of parenchyma cells such as interxylary phloem, xylem rays, and axial parenchyma. Regular changes in the conversion of starch grains to soluble sugars, the production of sesquiterpenoids, and other characteristic components of agarwood in various types of parenchyma cells were also observed. The material transformation was concentrated in the interxylary phloem, providing a structural and material basis for the formation of agarwood. It is the core part of the production of sesquiterpenoids and other characteristic products of agarwood. Compared with the A. sinensis inoculated for 12 months, the xylem of the A. sinensis inoculated for 18 months was more vigorous. There were no significant differences between the 12 and 18 months of inoculation in terms of sugars and agarwood characteristic products. In production, harvesting after 12 months of inoculation can improve harvesting efficiency.

Assessment of Fungal Concentrations Associated with Relative Humidity and Temperature Variations in the Indoor Environment

Background: Indoor environmental factors and human activities influence the presence and concentration of fungal propagules which may lead to the risk of developing respiratory infections and allergic reactions. Aim/Objectives: This study aimed to identify the factors that influence indoor fungal composition and determine its association with the development of respiratory and allergic reactions. Methodology: A total of 549 air samples and 226 nasal swabs of occupants were examined using health base questionnaire, malt extract agar and A6 single stage microbial air sampler. House dampness, mould growth on indoor materials, temperature, relative humidity, type of ventilation, type of human activity, and location of building were found to affect the prevalence and diversity of indoor fungi. Results: A total of 55, 46 and 50 species of fungi were isolated from homes, offices and hospitals respectively. High fungal count, were recorded in homes with moisture problems, low temperature and high relative humidity and homes located in high density areas. High cases of respiratory health problems were reported by occupants of these homes. Conclusion: Improvement in housing and establishment of awareness programmes can be used to lower fungal load and health problems associated with dampness in homes.It is necessary to maintain and prevent the housekeeping activities that can predispose fungal concentration in indoor environment.

Differential effects of indigenous arbuscular mycorrhizal fungi and phosphate solubilizing bacteria on maize growth in phosphate-fertilized and unfertilized acid soil

Biofertilizers may be developed using indigenous arbuscular mycorrhizal (AM) fungi and phosphatesolubilizing microorganisms (PSM) isolated from rhizosphere of maize grown on acid laterite soil in eastern India. Microbial colonies thus screened yielded a pigmented, gram negative eubacterial strain which solubilized P bound as ferric phosphate. Fungal inocula for AM were prepared from dried rootlets. Potcultivated maize seedlings were inoculated with PSM and AM fungal propagules under application of two levels of inorganic P (0 and 100 mg/kg soil). Analysis of shoot samples and rhizosphere soil harvested at 20 and 40 days after sowing (DAS) indicated that AM fungi efficiently acquired P for the seedlings in highly depleted soil, gaining over 186% shoot biomass over non-inoculated seedlings in P-0 condition. Inoculation with PSMs gave high concentrations of mobilized P in rhizosphere under P100 condition. Joint treatment with AM, PSM and P100 gave more than 32% increase in shoot dry weight at 40 DAS over solo P100 application – significantly higher than the next best level of shoot biomass obtained (12.4% over solo P100 application) at AM treatment under P0 condition. These results indicated opposite nutrient utilization strategies by AM fungi and PSM in maize rhizosphere, emphasizing holistic application of native biofertilizer components.

Quantifying the Role of Ground Beetles for the Dispersal of Fusarium and Alternaria Fungi in Agricultural Landscapes

The spread by arthropods (zoochory) is an essential dispersal mechanism for many microorganisms, like plant pathogens. Carabid beetles are very abundant and mobile ground-dwelling insects. However, their role in the dispersal of economically relevant phytopathogens, like Fusarium and Alternaria fungi is basically unknown. We quantified the total fungal, Fusarium, and Alternaria load of carabid species collected in the transition zones between small water bodies and wheat fields by screening (i) their body surface for fungal propagules with a culture-dependent method and (ii) their entire bodies for fungal DNA with a qPCR approach. The analysis of entire bodies detects fungal DNA in all carabid beetles but Alternaria DNA in 98% of them. We found that 74% of the carabids carried fungal propagules on the body surface, of which only half (49%) carried Fusarium propagules. We identified eight Fusarium and four Alternaria species on the body surface; F. culmorum was dominant. The fungal, Fusarium and Alternaria, load differed significantly between the carabid species and was positively affected by the body size and weight of the carabids. Carabid beetles reveal a remarkable potential to disseminate different fungi. Dispersal by ground-dwelling arthropods could affect the spatial-temporal patterns of plant disease and microorganisms in general.

Qualitative and Quantitative Characteristics of Soil Microbiome of Barents Sea Coast, Kola Peninsula

The soil microbiome of the Barents Sea coast of the Kola Peninsula is here characterized for the first time. The content of copies of ribosomal genes of archaea, bacteria, and fungi was determined by real-time PCR. Reserves and structure of biomass of soil microorganisms such as total biomass of fungi and prokaryotes, length and diameter of mycelium of fungi and actinomycetes, proportion of mycelium in biomass, number of spores and prokaryotic cells, proportion of small and large fungal propagules, and morphology of mycobiota spores were determined. The largest number of ribosomal gene copies was found for bacteria (from 6.47 × 109 to 3.02 × 1011 per g soil). The number of copies of ribosomal genes of fungi and archaea varied within 107–109 copies of genes/g soil. The biomass of microorganisms (prokaryotes and fungi in total) varied from 0.023 to 0.840 mg/g soil. The share of mycobiota in the microbial biomass ranged from 90% to 97%. The number of prokaryotes was not large and varied from 1.87 × 108 to 1.40 × 109 cells/g of soil, while the biomass of fungi was very significant and varied from 0.021 to 0.715 mg/g of soil. The length of actinomycete mycelium was small—from 0.77 to 88.18 m/g of soil, as was the length of fungal hyphae—an order of magnitude higher (up to 504.22 m/g of soil). The proportion of fungal mycelium, an active component of fungal biomass, varied from 25% to 89%. Most (from 65% to 100%) of mycobiota propagules were represented by specimens of small sizes, 2–3 microns. Thus, it is shown that, despite the extreme position on the mainland land of Fennoscandia, local soils had a significant number of microorganisms, on which the productivity of ecosystems largely depends.

Fungistatic Mechanism of Ammonia against Nematode-Trapping Fungus Arthrobotrys oligospora, and Strategy for This Fungus To Survive Ammonia

Soil fungistasis is a phenomenon in which the germination and growth of fungal propagules is widely inhibited in soil. Although fungistatic compounds are known to play important roles in the formation of soil fungistasis, how such compounds act on soil fungi remains little studied.

A modified semi-selective medium for isolation and enumeration of Pochonia chlamydosporia (Goddard) Zare & W. Gams

Pochonia chlamydosporia, is one of the most promising biological control agents for managing phytoparasitic nematodes. Isolation and enumeration of viable colonies of P. chlamydosporia from soil and other substrates without contamination is a major limitation, when commonly available nutrient media are used. Development of a suitable selective/semi-selective media by incorporating one or more inhibitors of microbial growth can facilitate isolation of the fungus. In vitro studies were carried out to test the compatibility of commonly used pesticides, namely, metalaxyl, metalaxyl-mancozeb, carbendazim, copper oxychloride, and chlorpyrifos with P. chlamydosporia. The fungus showed relatively high tolerance to higher doses of metalaxyl and carbendazim and was used in the modified medium for better suppression of other soil borne fungi. In the present study, Kerry’s semi-selective medium was modified and evaluated by counting the viable fungal propagules in different substrates (rice, farmyard manure, maize, rice bran, barley, and sorghum) and soil artificially inoculated with the fungus. The results showed that the modified Kerry’s semi-selective medium can effectively be used for isolation and quantification of P. chlamydosporia in routine studies.

Greater Mouse-Eared Bats (Myotis myotis) Hibernating in the Nietoperek Bat Reserve (Poland) as a Vector of Airborne Culturable Fungi

Bats can contribute to an increase of aeromycota in underground ecosystems and might be a vector/reservoir of microorganisms; however, there is no information about the number and species composition of fungi around hibernating bats. One of the most common species in Europe with direct human contact is the greater mouse-eared bat (Myotis myotis). The goal of our research was the first report of the airborne fungi present in the close vicinity of hibernating M. myotis in the Nietoperek bat reserve (Western Poland) by the use of culture-based techniques and genetic and phenotypic identifications. Aerobiological investigations of mycobiota under hibernating bats were performed on two culture media (PDA and YPG) and at two incubation temperatures (7 and 24 ± 0.5 °C). Overall, we detected 32 fungal species from three phyla (Ascomycota, Basidiomycota, and Zygomycota) and 12 genera. The application of YPG medium and the higher incubation temperature showed higher numbers of isolated fungal species and CFU. Penicillium spp. were dominant in the study, with spores found outside the underground hibernation site from 51.9% to 86.3% and from 56.7% to 100% inside the bat reserve. Penicillium chrysogenum was the most frequently isolated species, then Absidia glauca, Aspergillus fumigatus, A. tubingensis, Mortierella polycephala, Naganishia diffluens, and Rhodotorula mucilaginosa. Temperature, relative humidity, and the abundance of bats correlated positively with the concentration of airborne fungal propagules, between fungal species diversity, and the concentration of aeromycota, but the number of fungal species did not positively correlate with the number of bats. The air in the underground site was more contaminated by fungi than the air outside; however, the concentration of aeromycota does not pose a threat for human health. Nevertheless, hibernating bats contribute to an increase in the aeromycota and as a vector/reservoir of microscopic fungi, including those that may cause allergies and infections in mammals, and should be monitored.

Harpophora maydis (late wilt of maize).

H. maydis is a soilborne and apparently seedborne fungus, related to the root-infecting species in the genus Gaeumannomyces. It is known from only a few scattered countries, where it can cause significant losses, but may have been unobserved in others in which the primary host, maize [Zea mays], is grown. This fungus was reported recently from Portugal and Spain (Molinero-Ruiz et al., 2010). No dispersal by fungal propagules has been demonstrated, so that, other than in soil, its likely means of spread over borders would be in seed. Importation of the fungus with seed is considered to be the source in Hungary (Pécsi and Németh, 1998). Although research has been carried out on chemical and biological control methods, the development and use of resistant varieties is the most practical means of control. Regulation and testing of imported seed should prevent transport of the pathogen to new regions.

UV-B Radiation Tolerance and Temperature-Dependent Activity Within the Entomopathogenic Fungal Genus Metarhizium in Brazil

Metarhizium comprises a phylogenetically diverse genus of entomopathogenic fungi. In Brazil, Metarhizium anisopliae s.str. subclade Mani 2 is predominantly isolated from insects, while M. robertsii and M. brunneum mostly occur in the soil environment. Solar radiation and high temperatures are important abiotic factors that can be detrimental to fungal propagules. We hypothesized that among 12 Brazilian isolates of Metarhizium spp., M. anisopliae Mani 2 (n = 6), being adapted to abiotic conditions of the phylloplane, is more tolerant to UV light and high temperatures than M. robertsii (n = 3) and M. brunneum (n = 3). Inoculum of each isolate was exposed to UV-B for up to 8 h and viability evaluated 48 h later. After 8 h under UV-B, most of the isolates had germination rates below 5%. Discs of mycelia were incubated at different temperatures, and diameter of colonies were recorded for 12 days. Mycelia of M. robertsii isolates grew faster at 33 °C, while M. anisopliae and M. brunneum grew most at 25 °C. Dry conidia were incubated at 20, 25 or 40 °C for 12 days, and then viabilities were examined. At 40 °C, conidia of five M. anisopliae isolates were the most tolerant. In the three experiments, considerable intra- and inter-specific variability was detected. The results indicate that conclusions about tolerance to these abiotic factors should be made only at the isolate level.