Ecology and diversity of leaf litter fungi during early-stage decomposition in a seasonally dry tropical forest

Bottlebrush and Myrtle twig canker caused by Neopestalotiopsis species: an emerging canker-causing group of fungi in Italy

Pestalotioid fungi were isolated in pure culture from symptomatic plants of Callistemonlaevis, C.viminalis, Lumaapiculata (marketed as "Myrtusluma"), Myrtuscommunissubsp.tarentina, and M.communisvar.microphylla (M.communis 'Microphylla'), showing twig canker, dieback and defoliation. The isolates were identified to species by ITS, tef1 and tub2 sequences, which revealed the presence of six species of Neopestalotiopsis (N.camelliae-oleiferae, N.hispanica, N.iberica, N.rosae, N.rosicola, and N.zakeelii) and one species of Pestalotiopsis (P.biciliata). While most species were isolated only once or twice, the majority of isolates belonged to N.rosae (13) and N.hispanica (8). Pathogenicity was investigated by pathogenicity tests on all hosts, which confirmed the pathogenicity of all Neopestalotiopsis species on at least some of the hosts tested, while P.biciliata did not cause any disease symptoms. Neopestalotiopsishispanica and N.rosae caused symptoms in all hosts of the present study, while the other Neopestalotiopsis species tested showed no symptoms on Lumaapiculata.

Tree phylogeny predicts more than litter chemical components in explaining enzyme activities in forest leaf litter decomposition

Litter decomposition is an important process in ecosystem and despite recent research elucidating the significant influence of plant phylogeny on plant-associated microbial communities, it remains uncertain whether a parallel correlation exists between plant phylogeny and the community of decomposers residing in forest litter. In this study, we conducted a controlled litterbag experiment using leaf litter from ten distinct tree species in a central subtropical forest ecosystem in a region characterized by subtropical humid monsoon climate in China. The litterbags were placed in situ using a random experimental design and were collected after 12 months of incubation. Then, the litter chemical properties, microbial community composition and activities of enzyme related to the decomposition of organic carbon (C) and nitrogen (N) were assessed. Across all ten tree species, Alphaproteobacteria, Gammaproteobacteria, and Actinobacteria were identified as the predominant bacterial classes, while the primary fungal classes were Dothideomycetes, Sordariomycetes and Eurotiomycetes. Mantel test revealed significant correlations between litter chemical component and microbial communities, as well as enzyme activities linked to N and C metabolism. However, after controlling for plant phylogenetic distance in partial Mantel test, the relationships between litter chemical component and microbial community structure and enzyme activities were not significant. Random forest and structural equation modeling indicated that plant phylogenetic distance exerted a more substantial influence than litter chemical components on microbial communities and enzyme activities associated with the decomposition of leaf litter. In summary, plant phylogenic divergence was found to be a more influential predictor of enzyme activity variations than microbial communities and litter traits, which were commonly considered reliable indicators of litter decomposition and ecosystem function, thereby highlighting the previously underestimated significance of plant phylogeny in shaping litter microbial communities and enzyme activities associated with degradation processes in forest litter.

Isolation and characterization of thermostable and alkali-tolerant cellulase from litter endophytic fungus Bartalinia pondoensis

Endophytic fungi in plant tissues produce a wide range of secondary metabolites and enzymes, which exhibit a variety of biological activities. In the present study, litter endophytic fungi were isolated from a fire-prone forest and screened for thermostable cellulases. Among nine endophytic fungi tested, two isolates, Bartalinia pondoensis and Phoma sp., showed the maximum cellulase activity. Bartalinia pondoensis was further selected for its cellulase production and characterization. Among the carbon and nitrogen sources tested, maximum cellulase production was observed with maltose and yeast extract, and the eucalyptus leaves and rice bran served as the best natural substrates. The cellulase activity increased with increasing temperature, with maximum activity recorded at 100 °C. The maximum CMCase activity was observed between pH 6.0 and 7.0 and retained 80% of its activity in the pH range of 8-10. Partially purified cellulase of B. pondoensis retained 50% of its activity after 2 h of incubation at 60 °C, 80 °C and 100 °C. These results suggest that litter endophytic fungus B. pondoensis is a potential source for the production of thermostable and alkali-tolerant cellulase.

Predicting global numbers of teleomorphic ascomycetes

Sexual reproduction is the basic way to form high genetic diversity and it is beneficial in evolution and speciation of fungi. The global diversity of teleomorphic species in Ascomycota has not been estimated. This paper estimates the species number for sexual ascomycetes based on five different estimation approaches, viz. by numbers of described fungi, by fungus:substrate ratio, by ecological distribution, by meta-DNA barcoding or culture-independent studies and by previous estimates of species in Ascomycota. The assumptions were made with the currently most accepted, “2.2–3.8 million” species estimate and results of previous studies concluding that 90% of the described ascomycetes reproduce sexually. The Catalogue of Life, Species Fungorum and published research were used for data procurement. The average value of teleomorphic species in Ascomycota from all methods is 1.86 million, ranging from 1.37 to 2.56 million. However, only around 83,000 teleomorphic species have been described in Ascomycota and deposited in data repositories. The ratio between described teleomorphic ascomycetes to predicted teleomorphic ascomycetes is 1:22. Therefore, where are the undiscovered teleomorphic ascomycetes? The undescribed species are no doubt to be found in biodiversity hot spots, poorly-studied areas and species complexes. Other poorly studied niches include extremophiles, lichenicolous fungi, human pathogens, marine fungi, and fungicolous fungi. Undescribed species are present in unexamined collections in specimen repositories or incompletely described earlier species. Nomenclatural issues, such as the use of separate names for teleomorph and anamorphs, synonyms, conspecific names, illegitimate and invalid names also affect the number of described species. Interspecies introgression results in new species, while species numbers are reduced by extinctions.

Diversity of saprotrophic filamentous fungi on Araucaria angustifolia (Bertol.) Kuntze (Brazilian pine)

The biodiversity of filamentous fungi and their ecological relationships in the context of decaying Araucaria angustifolia (an endangered conifer) substrates are still mostly unknown. The present study aimed to investigate the diversity of saprotrophic filamentous fungi, based on morphological identification, associated with A. angustifolia, in addition to assessing possible saprobic/plant affinity relationship, and verifying whether the study areas and substrates affect the composition of the mycobiota. A total of 5000 substrates (decaying needles and twigs) were collected during five expeditions (2014/2015) to two areas: São Francisco de Paula National Forest (FLONA-SFP) and São Joaquim National Park (PARNA-SJ), Brazil. A total of 135 species distributed among 85 genera, 40 families, nine classes, 24 orders, three subphyla, and two phyla were identified. One new genus and five new species that were previously described, and six rare species and five species with affinity for A. angustifolia were also recorded. The twigs showed a community of fungi with greater richness and dominance. Conversely, the values of abundance, Simpson's diversity index, and evenness were lower than those determined for needles. In terms of the study areas, FLONA-SFP showed higher values of richness, abundance, Simpson's diversity index, and evenness than PARNA-SJ. Principal coordinate analysis and similarity percentage analysis showed the influence of both substrate factors and areas in the composition of the fungal communities. The presence of new, rare, and affinity-related species reinforces the study of fungi in the context of the conservation of this conifer, as these species are threatened by co-extinction.

Role of Leaf Litter in Above-Ground Wood Decay

The effects of leaf litter on moisture content and fungal decay development in above-ground wood specimens were assessed. Untreated southern pine specimens were exposed with or without leaf litter contact. Two types of leaf litter were evaluated; aged (decomposed) and young (early stages of decomposition). The moisture content of specimens was monitored, and specimens were periodically removed for visual evaluation of decay development. In addition, amplicon-based sequencing analysis of specimens and associated leaf litter was conducted at two time points. Contact with either type of leaf litter resulted in consistently higher moisture contents than those not in contact with leaf litter. Visually, evident decay developed most rapidly in specimens in contact with the aged leaf litter. Analysis of amplicon-based sequencing revealed that leaf litter contributes a significant amount of the available wood decay fungal community with similar communities found in the litter exposed wood and litter itself, but dissimilar community profiles from unexposed wood. Dominant species and guild composition shifted over time, beginning initially with more leaf saprophytes (ascomycetes) and over time shifting to more wood rotting fungi (basidiomycetes). These results highlight the importance of the contributions of leaf litter to fungal colonization and subsequent decay hazard for above-ground wood.

Do Foliar Endophytes Matter in Litter Decomposition?

Litter decomposition rates are affected by a variety of abiotic and biotic factors, including the presence of fungal endophytes in host plant tissues. This review broadly analyzes the findings of 67 studies on the roles of foliar endophytes in litter decomposition, and their effects on decomposition rates. From 29 studies and 1 review, we compiled a comprehensive table of 710 leaf-associated fungal taxa, including the type of tissue these taxa were associated with and isolated from, whether they were reported as endo- or epiphytic, and whether they had reported saprophytic abilities. Aquatic (i.e., in-stream) decomposition studies of endophyte-affected litter were significantly under-represented in the search results (p < 0.0001). Indicator species analyses revealed that different groups of fungal endophytes were significantly associated with cool or tropical climates, as well as specific plant host genera (p < 0.05). Finally, we argue that host plant and endophyte interactions can significantly influence litter decomposition rates and should be considered when interpreting results from both terrestrial and in-stream litter decomposition experiments.

Characterization of an ionic liquid-tolerant β-xylosidase from a marine-derived fungal endophyte

Ionic liquids (ILs) are used in lignocellulosic biomass (LCB) pretreatment because of their ability to disrupt the extensive hydrogen-bonding network in cellulose and hemicellulose, and thereby decrease LCB recalcitrance to subsequent enzymatic degradation. However, this approach necessitates the development of cellulases and hemicellulases that can tolerate ∼20% (w/v) IL, an amount that either co-precipitates with the sugar polymers after the initial pretreatment or is typically used in single-pot biomass deconstructions. By investigating the secretomes from 4 marine-derived fungal endophytes, we identified a β-xylosidase derived from Trichoderma harzianum as the most promising in terms of tolerating 1-ethyl-3-methylimidazolium-dimethyl phosphate (EMIM-DMP), an IL. When tested with p-nitrophenyl-β-d-xyloside, this extracellular xylosidase retained ∼50% activity even in 1.2 mol·L–1 (20% w/v) EMIM-DMP after incubation for 48 h. When tested on the natural substrate xylobiose, there was ∼85% of the initial activity in 1.2 mol·L–1 EMIM-DMP after incubation for 9 h and ∼80% after incubation for 48 h. Despite previous findings associating thermostability and IL tolerance, our findings related to the mesophilic T. harzianum β-xylosidase(s) emphasize the need to include the marine habitat in the bioprospecting dragnet for identification of new IL-tolerant LCB-degrading enzymes.