Ravi L. C. Wijesundera

Bio: Ravi L. C. Wijesundera is an academic researcher from University of Colombo. The author has contributed to research in topics: Plant use of endophytic fungi in defense & Sodium bicarbonate. The author has an hindex of 13, co-authored 23 publications receiving 2358 citations.

Global diversity and geography of soil fungi

Abstract: Fungi play major roles in ecosystem processes, but the determinants of fungal diversity and biogeographic patterns remain poorly understood. Using DNA metabarcoding data from hundreds of globally distributed soil samples, we demonstrate that fungal richness is decoupled from plant diversity. The plant-to-fungus richness ratio declines exponentially toward the poles. Climatic factors, followed by edaphic and spatial variables, constitute the best predictors of fungal richness and community composition at the global scale. Fungi show similar latitudinal diversity gradients to other organisms, with several notable exceptions. These findings advance our understanding of global fungal diversity patterns and permit integration of fungi into a general macroecological framework.

New species from the Fusarium solani species complex derived from perithecia and soil in the old World tropics.

Abstract: A large collection of strains belonging to the Fusarium solani species complex (FSSC) was isolated from soil and perithecia in primary forests in Sri Lanka (from fallen tree bark) and tropical Australia (Queensland, from fallen tree fruits and nuts). Portions of the translation elongation factor 1-alpha (tef1) gene, the nuclear large subunit (NLSU) and internal transcribed spacer regions (ITS) of the nuclear ribosomal RNA genes were sequenced in 52 isolates from soil and perithecia. The FSSC was divided previously into three clades with some biogeographic structure, termed Clades 1, 2 and 3. All Sri Lankan and Australian soil isolates were found to be members of Clade 3, most grouping with the cosmopolitan soil-associated species F. falciforme. All but two Sri Lankan perithecial isolates were associated with a set of five divergent phylogenetic lineages that were associated with Clade 2. Australian perithecial isolates resided in a subclade of Clade 3 where most of the previously defined mating population...

Effect of ammonium carbonate and sodium bicarbonate on anthracnose of papaya

Abstract: Colletotrichum gloeosporioides is the causal organism of anthracnose inCarica papaya L. (papaya, papaw). The effect of ammonium carbonate (3%) or sodium bicarbonate (2%) in aqueous solution or when incorporated into a wax formulation on anthracnose severity in inoculated or naturally infected fruits was examined. Both salts had significant effects, but that of ammonium carbonate was greater than that of sodium bicarbonate in controlling anthracnose. Ammonium carbonate (3%) incorporated into the wax formulation effectively reduced anthracnose incidence by 70% in naturally infected papaya and extended the storage life by maintaining the firmness, color and overall quality of the fruit in low temperature storage (13.5°C) and 95% r.h. for 21 days followed by 2 days under marketing conditions. The mode of action of ammonium carbonate on the control of anthroacnose appears to bevia complete inhibition of radial mycelial growth and conidia germination.

Helvolic acid, an antibacterial nortriterpenoid from a fungal endophyte, Xylaria sp. of orchid Anoectochilus setaceus endemic to Sri Lanka.

Abstract: An endophytic fungus was isolated from surface sterilized leaf segments of Anoectochilus setaceus, an orchid endemic to Sri Lanka, and was identified as Xylaria sp. by morphological characters and DNA sequencing. Bioassay-guided chromatographic fractionation of the organic extract of a laboratory culture of this fungus led to the isolation of the known antibacterial helvolic acid. Helvolic acid was active against the Gram-positive bacteria, Bacillus subtilis [minimal inhibitory concentrations (MIC), 2 μg mL−1] and methicillin-resistant Staphylococcus aureus (MIC, 4 μg mL−1).

Embracing the unknown: disentangling the complexities of the soil microbiome.

Abstract: Soil microorganisms are clearly a key component of both natural and managed ecosystems. Despite the challenges of surviving in soil, a gram of soil can contain thousands of individual microbial taxa, including viruses and members of all three domains of life. Recent advances in marker gene, genomic and metagenomic analyses have greatly expanded our ability to characterize the soil microbiome and identify the factors that shape soil microbial communities across space and time. However, although most soil microorganisms remain undescribed, we can begin to categorize soil microorganisms on the basis of their ecological strategies. This is an approach that should prove fruitful for leveraging genomic information to predict the functional attributes of individual taxa. The field is now poised to identify how we can manipulate and manage the soil microbiome to increase soil fertility, improve crop production and improve our understanding of how terrestrial ecosystems will respond to environmental change.

Mycorrhizal ecology and evolution: the past, the present, and the future

Abstract: Almost all land plants form symbiotic associations with mycorrhizal fungi. These below-ground fungi play a key role in terrestrial ecosystems as they regulate nutrient and carbon cycles, and influence soil structure and ecosystem multifunctionality. Up to 80% of plant N and P is provided by mycorrhizal fungi and many plant species depend on these symbionts for growth and survival. Estimates suggest that there are c. 50 000 fungal species that form mycorrhizal associations with c. 250 000 plant species. The development of high-throughput molecular tools has helped us to better understand the biology, evolution, and biodiversity of mycorrhizal associations. Nuclear genome assemblies and gene annotations of 33 mycorrhizal fungal species are now available providing fascinating opportunities to deepen our understanding of the mycorrhizal lifestyle, the metabolic capabilities of these plant symbionts, the molecular dialogue between symbionts, and evolutionary adaptations across a range of mycorrhizal associations. Large-scale molecular surveys have provided novel insights into the diversity, spatial and temporal dynamics of mycorrhizal fungal communities. At the ecological level, network theory makes it possible to analyze interactions between plant-fungal partners as complex underground multi-species networks. Our analysis suggests that nestedness, modularity and specificity of mycorrhizal networks vary and depend on mycorrhizal type. Mechanistic models explaining partner choice, resource exchange, and coevolution in mycorrhizal associations have been developed and are being tested. This review ends with major frontiers for further research.

Microbial diversity drives multifunctionality in terrestrial ecosystems

Abstract: Despite the importance of microbial communities for ecosystem services and human welfare, the relationship between microbial diversity and multiple ecosystem functions and services (that is, multifunctionality) at the global scale has yet to be evaluated. Here we use two independent, large-scale databases with contrasting geographic coverage (from 78 global drylands and from 179 locations across Scotland, respectively), and report that soil microbial diversity positively relates to multifunctionality in terrestrial ecosystems. The direct positive effects of microbial diversity were maintained even when accounting simultaneously for multiple multifunctionality drivers (climate, soil abiotic factors and spatial predictors). Our findings provide empirical evidence that any loss in microbial diversity will likely reduce multifunctionality, negatively impacting the provision of services such as climate regulation, soil fertility and food and fibre production by terrestrial ecosystems.

Structure and function of the global topsoil microbiome.

Abstract: Soils harbour some of the most diverse microbiomes on Earth and are essential for both nutrient cycling and carbon storage. To understand soil functioning, it is necessary to model the global distribution patterns and functional gene repertoires of soil microorganisms, as well as the biotic and environmental associations between the diversity and structure of both bacterial and fungal soil communities1–4. Here we show, by leveraging metagenomics and metabarcoding of global topsoil samples (189 sites, 7,560 subsamples), that bacterial, but not fungal, genetic diversity is highest in temperate habitats and that microbial gene composition varies more strongly with environmental variables than with geographic distance. We demonstrate that fungi and bacteria show global niche differentiation that is associated with contrasting diversity responses to precipitation and soil pH. Furthermore, we provide evidence for strong bacterial–fungal antagonism, inferred from antibiotic-resistance genes, in topsoil and ocean habitats, indicating the substantial role of biotic interactions in shaping microbial communities. Our results suggest that both competition and environmental filtering affect the abundance, composition and encoded gene functions of bacterial and fungal communities, indicating that the relative contributions of these microorganisms to global nutrient cycling varies spatially.