Biocrusts inside and outside of Mimosa luisana resource islands as reservoirs of arbuscular mycorrhizal fungi in a Mexican semiarid ecosystem

Background: Arbuscular mycorrhizal fungi (AMF) and biocrusts (BC), occur inside and outside Mimosa luisana resource islands (M. luisana-RI) at the Tehuacán-Cuicatlán Valley, Puebla-Oaxaca, Mexico. Objectives: To determine: 1) Whether there are AMF within biocrusts, 2) The abundance and richness of AMF, and 3) The potential of AMF propagation in BC and soil below BC inside (BC-RI, soil-BC-RI) and outside (BC-ORI, soil-BC-ORI) M. luisana-RI, and open areas (OA), in the rainy (September 2011) and dry (May 2012) seasons. Methods: AMF were extracted of biocrusts and soil samples collected inside and outside M. luisana-RI and OA, in both seasons. Spore abundance and species richness, as well as potential propagation of AMF were determined in laboratory and greenhouse. Results and Conclusions: Biocrusts inside and outside M. luisana-RI form reservoirs of AMF spores and species richness (12 spp.), and act as “shields” protecting AMF compared with OA (5 spp.). Seasonal changes in the AMF composition within the biocrusts and the soil suggest that the availability of water drives AMF assemblages. The AM fungal spores in BC-RI and BC-ORI have a high potential of propagation; however, the BC-ORI by buffering the loss of AMF in soil-BC-ORI, they form mycorrhizal inocula within the soil.

Ecological Regulation of Black Leaf Streak Disease Driven by Plant Richness in Banana Agroecosystems

Black leaf streak disease (BLSD), caused by the fungus Mycosphaerella fijiensis, is an important threat to banana production. Although its control relies on costly and unsustainable use of fungicides, ecological regulation of BLSD linked to field-scale plant diversity has received little attention. We monitored banana phytometers in plots in banana-based fields where no fungicides were applied. Within each plot, we measured plant richness in three strata, canopy openness, necrotic leaf removal, Musa abundance and richness. We quantified ecological regulation of five BLSD parameters (inoculum sources, spore abundance, lesion density, incubation time, and the area under the disease progression curve) and identified, using structural equation modeling, the characteristics of the plant community and the mechanisms likely responsible for the regulation. Regulation occurred, but most effectively before lesion formation, and was mainly related to plant richness between 1.5 and 5m high. A barrier effect, rather than a dilution effect, more likely limited spore abundance. Our results support the hypothesis that the potential effects of plant richness on leaf-scale microclimate variability and on the diversity of epiphyllic microorganisms are involved in the regulation of incubation time and lesion density. Field-scale management of plant diversity may be a promising lever to foster ecological regulation of BLSD.

Mushroom Emergence Detected by Combining Spore Trapping with Molecular Techniques

ABSTRACT Obtaining reliable and representative mushroom production data requires time-consuming sampling schemes. In this paper, we assessed a simple methodology to detect mushroom emergence by trapping the fungal spores of the fruiting body community in plots where mushroom production was determined weekly. We compared the performance of filter paper traps with that of funnel traps and combined these spore trapping methods with species-specific quantitative real-time PCR and Illumina MiSeq to determine the spore abundance. Significantly more MiSeq proportional reads were generated for both ectomycorrhizal and saprotrophic fungal species using filter traps than were obtained using funnel traps. The spores of 37 fungal species that produced fruiting bodies in the study plots were identified. Spore community composition changed considerably over time due to the emergence of ephemeral fruiting bodies and rapid spore deposition (lasting from 1 to 2 weeks), which occurred in the absence of rainfall events. For many species, the emergence of epigeous fruiting bodies was followed by a peak in the relative abundance of their airborne spores. There were significant positive relationships between fruiting body yields and spore abundance in time for five of seven fungal species. There was no relationship between fruiting body yields and their spore abundance at plot level, indicating that some of the spores captured in each plot were arriving from the surrounding areas. Differences in fungal detection capacity by spore trapping may indicate different dispersal ability between fungal species. Further research can help to identify the spore rain patterns for most common fungal species. IMPORTANCE Mushroom monitoring represents a serious challenge in economic and logistical terms because sampling approaches demand extensive field work at both the spatial and temporal scales. In addition, the identification of fungal taxa depends on the expertise of experienced fungal taxonomists. Similarly, the study of fungal dispersal has been constrained by technological limitations, especially because the morphological identification of spores is a challenging and time-consuming task. Here, we demonstrate that spores from ectomycorrhizal and saprotrophic fungal species can be identified using simple spore traps together with either MiSeq fungus-specific amplicon sequencing or species-specific quantitative real-time PCR. In addition, the proposed methodology can be used to characterize the airborne fungal community and to detect mushroom emergence in forest ecosystems.

Succession of arbuscular mycorrhizal fungi in a deflation hollow of the Słowiński National Park, Poland

In the years 1994-1995, the occurrence of arbuscular mycorrhizal fungi (AMF) and arbuscular mycorrhizae (AM) in eight successional stages of vegetation of a deflation hollow no. 12 of the Łeba Bar, Poland, was investigated. Early successional stages were colonized by members of the families Gramineae and Juncaceae, being gradually replaced by ericaceous plants in the middle and later stages and by trees in the most advanced stage corresponding to the <em>Empetro nigri-Pinetum</em> plant association. From the 96 soil samples collected, 21 species in three genera of AMF were recovered. The fungi most frequently found were members of the genus <em>Acaulospora</em>. The overall spore abundance, the species_ richness of AMF and the level of AM colonisation increased from stage 1 to reach a maximum in the middle stages and then gradually declined, being lowest in the forested stage 8. The values of the overall spore abundance and those of the abundances of the most frequently occurring AMF species strongly evidenced functioning in nature of the process of host-dependent differentiation of AMF communities. Of the five most numerously represented AMF species, the early colonizer and quickly diminishing in later successional stages was <em>Glomus</em> 107. The mid-late successor was <em>A. koskei</em>, and the latest - <em>Glomus aggregatum</em>. All measures of AMF presence negatively correlated with the content of organic C in the soil and most of them were negatively correlated with soil N-NO3 and P concentrations. In contrast, the occurrence of AMY and AM generally was positively correlated with soil pH and the K content of the soil.

Field Evaluation of Arbuscular Mycorrhizal Fungal Colonization in Bacillus thuringiensis Toxin-Expressing (Bt) and Non-Bt Maize

ABSTRACTThe cultivation of genetically engineeredBacillus thuringiensistoxin-expressing (Bt) maize continues to increase worldwide, yet the effects of Bt crops on arbuscular mycorrhizal fungi (AMF) in soil are poorly understood. In this field experiment, we investigated the impact of seven different genotypes of Bt maize and five corresponding non-Bt parental cultivars on AMF and evaluated plant growth responses at three different physiological time points. Plants were harvested 60 days (active growth), 90 days (tasseling and starting to produce ears), and 130 days (maturity) after sowing, and data on plant growth responses and percent AMF colonization of roots at each harvest were collected. Spore abundance and diversity were also evaluated at the beginning and end of the field season to determine whether the cultivation of Bt maize had a negative effect on AMF propagules in the soil. Plant growth and AMF colonization did not differ between Bt and non-Bt maize at any harvest period, but AMF colonization was positively correlated with leaf chlorophyll content at the 130-day harvest. Cultivation of Bt maize had no effect on spore abundance and diversity in Bt versus non-Bt plots over one field season. Plot had the most significant effect on total spore counts, indicating spatial heterogeneity in the field. Although previous greenhouse studies demonstrated that AMF colonization was lower in some Bt maize lines, our field study did not yield the same results, suggesting that the cultivation of Bt maize may not have an impact on AMF in the soil ecosystem under field conditions.