Category: MycoKeys

New fungus found to cause cankers and declines in pistachio trees in Sicily, Italy

Starting in the spring of 2010, farmers from Sicily – the major pistachio production area of Italy – have been reporting a previously unknown disease on the trees. Characterised by cankers and declines, it sometimes leads to the collapse of the entire plant.

When the research team led by Salvatore Vitale, Centro di Ricerca Difesa e Certificazione, Italy, studied plants from a total of 15 pistachio orchards in Catania, Agrigento and Caltanissetta provinces, they identified cankers associated with vascular necrosis and tree decline on twigs, branches and stems, alongside abundant gummosis. There were also localised, sunken lesions with several central cracks. These lesions would deepen into the woody tissue, where discolouration and necrotic tissue were also present.

Additionally, the scientists conducted a series of pathogenicity tests on 5-year-old potted pistachio plants (Pistacia vera), which successfully reproduced the field observations. As a result, a previously unknown pathogenic fungus, which colonises the woody plant tissue, has been isolated.

*Timelapse of the symptoms reproduced in a potted plant.*

The aetiology of the disease and the description of the new species, named Liberomyces pistaciae, are published in the open access journal MycoKeys. Despite cankers and subsequent decline of pistachio trees having been observed in Sicily for several years, the paper is the first work to successfully determine the causal agent.

“On the basis of the high disease incidence and the frequency of this species observed in several orchards in the last years, we believe that L. pistaciae represents amenace to pistachio production in Sicily,” say the researchers.

*Symptoms caused by the newly described pathogenic fungus observed in the field.*

Out of the 15 surveyed orchards, the scientists detected the presence of the fungus in ten of them. Most of the observations occurred in the winter period and during late spring, but the authors found the pathogen in asymptomatic trees as well, which suggests that the fungus has a dormant growth phase.

When already symptomatic, the plants begin to exudate gum. Often, the bark on their trunks and/or branches would scale, appearing as if cracking and peeling. The initial pale circular areas present in the bark turn dark and sunken with time. Later, the infected patches were seen to expand in all directions, yet faster along the main axis of the stems, branches and twigs. When the scientists examined beneath the bark, they saw discoloured and necrotic tissues. Once the trunk of the tree is encircled by a canker, they report, the whole plant collapses.

Other symptoms include canopy decline as well as wilting and dying inflorescences and shoots growing from infected branches or twigs.

The newly described fungus is characterised with slowly growing colonies. With time, they turn from white to pale to dark brown with a whitish slightly lobed margin.

The researchers warn that essential hazard for the further spread and promotion of the infection is the use and distribution of infected propagation material taken from nurseries and mechanical injuries or pruning wounds.

Further research and studies are currently in progress aiming to extend the survey to other areas in order to eventually formulate effective disease management strategies.

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Original source:

Vitale S, Aiello D, Guarnaccia V, Luongo L, Galli M, Crous PW, Polizzi G, Belisario A, Voglmayr H (2018) Liberomyces pistaciae sp. nov., the causal agent of pistachio cankers and decline in Italy. MycoKeys 40: 29-51. https://doi.org/10.3897/mycokeys.40.28636

The Alps are home to more than 3,000 lichens

Historically, the Alps have always played an emblematic role, being one of the largest continuous natural areas in Europe. With its numerous habitats, the mountain system is easily one of the richest biodiversity hotspots in Europe.

Lichens are curious organisms comprising a stable symbiosis between a fungus and one or more photosynthetic organisms, for example green algae and/or cyanobacteria. Once the symbiosis is established, the new composite organism starts to function as a whole new one, which can now convert sunlight into essential nutrients and resist ultraviolet light at the same time.

A common fruticose lichen in the Alps (Flavocetraria nivalis). Photo: Dr Peter O. Bilovitz — *A common fruticose lichen in the Alps (Flavocetraria nivalis).*
*Photo: Dr Peter O. Bilovitz*

Being able to grow on a wide range of surfaces – from tree bark to soil and rock, lichens are extremely useful as biomonitors of air quality, forest health and climate change.

Nevertheless, while the Alps are one of the best studied parts of the world in terms of their biogeography, no overview of the Alpine lichens had been provided up until recently, when an international team of lichenologists, led by Prof. Pier Luigi Nimis, University of Trieste, Italy, concluded their 15-year study with a publication in the open access journal MycoKeys.

Sunrise in the Julian Alps. Photo: Dr Pier Luigi Nimis — *Sunrise in the Julian Alps.*
*Photo: Dr Pier Luigi Nimis*

The scientists’ joint efforts produced the first ever checklist to provide a complete critical catalogue of all lichens hitherto reported from the Alps. It comprises a total of 3,138 entries, based on data collected from eight countries – Austria, France, Germany, Italy, Liechtenstein, Monaco, Slovenia and Switzerland. In their research paper, the authors have also included notes on the lichens’ ecology and taxonomy.

A common lichen in the Alps (Xanthoria elegans). Photo: Dr Tomi Trilar — *A common lichen in the Alps (Xanthoria elegans).*
*Photo: Dr Tomi Trilar*

They point out that such catalogue has been missing for far too long, hampering research all over the world. The scientists point out that this has been “particularly annoying”, since the data from the Alps could have been extremely useful for comparisons between mountainous lichen populations from around the globe. It turns out that many lichens originally described from the Alps have been later identified in other parts of the world.

“It was a long and painstaking work, which lasted almost 15 years, revealing a surprisingly high number of yet to be resolved taxonomic problems that will hopefully trigger further research in the coming years,” say the authors.

“We think that the best criterion to judge whether a checklist has accomplished its task for the scientific community is the speed of it becoming outdated,” they conclude paradoxically.

The new checklist is expected to serve as a valuable tool for retrieving and accessing the enormous amount of information on the lichens of the Alps

A widespread alpine lichen (Thamnolia vermicularis). Photo: Dr Peter O. Bilovitz — *A widespread alpine lichen (Thamnolia vermicularis).*
*Photo: Dr Peter O. Bilovitz*

that has accumulated over centuries of research. It offers a basis for specimen revisions, critical re-appraisal of poorly-known species and further exploration of under-explored areas. Thus, it could become a catalyst for new, more intensive investigations and turn into a benchmark for comparisons between mountains systems worldwide.

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Original source:

Nimis PL, Hafellner J, Roux C, Clerc P, Mayrhofer H, Martellos S, Bilovitz PO (2018) The lichens of the Alps – an annotated checklist. MycoKeys 31: 1-634. https://doi.org/10.3897/mycokeys.31.23568

Lichenologists at work in the Carnic Alps. Photo: Dr Pier Luigi Nimis — *Lichenologists at work in the Carnic Alps.*
*Photo: Dr Pier Luigi Nimis*

Underwater mushrooms: Curious lake fungi under every turned over stone

While fungi are well known for being essential in cycling carbon and nutrients, there are only about 100,000 described species in contrast to the 1.5 to 3 millions, assumed to exist on Earth. Of these, barely 3000 fungi belong to aquatic habitats. In fact, freshwater fungi have been researched so little, it is only now that an international research team provide the first lake-wide fungal diversity estimate in the open access journal MycoKeys.

Over the spring and the early summer of 2010, a large team of scientists, led by Dr Christian Wurzbacher and Dr Norman Warthmann, affiliated with the Leibniz-Institute of Freshwater Ecology and Inland Fisheries and the Berlin Center for Genomics in Biodiversity Research, Germany (currently at University of Gothenburg, Sweden, and the Australian National University, Australia, respectively), collected a total of 216 samples from 54 locations, encompassing eight different habitats within Lake Stechlin in North-East Germany.

Having recovered samples on three occasions over the course of the study, their aim was to test how habitat specificity affects the fungal community and whether fungal groups would reflect the availability of particulate organic matter as substrate. Unlike previous studies of aquatic fungi that compared water samples among different lakes or seasons, theirs would compare the diversity among habitats within a single lake. This included the study of fungi living in the water and the sediments, as well as fungi living on the surfaces of plants and other animals.

As a result, the scientists concluded that every type of habitat, i.e. sediments, biofilms, and submerged macrophytes (large aquatic plants), has a specific fungal community that varies more than initially expected. Of these, lake biofilms, representing a group of microorganisms, whose cells stick to each other, and cling together to a surface, turned out to be the hotspots for aquatic fungi.

“Our study provides the first estimate of lake-wide fungal diversity and highlights the important contribution of habitat heterogeneity to overall diversity and community composition,” the scientists summarise. “Habitat diversity should be considered in any sampling strategy aiming to assess the fungal diversity of a water body.”

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Original source:

Wurzbacher C, Warthmann N, Bourne EC, Attermeyer K, Allgaier M, Powell JR, Detering H, Mbedi S, Grossart H-P, Monaghan MT (2016) High habitat-specificity in fungal communities in oligo-mesotrophic, temperate Lake Stechlin (North-East Germany). MycoKeys 16: 17-44. https://doi.org/10.3897/mycokeys.16.9646

Top 50 most wanted fungi: New search function zooms in on the dark fungal diversity

There are many millions of undescribed fungi, and public DNA sequence databases contain thousands of fungal sequences that cannot be assigned to any known fungal group with confidence. Many of these sequences have defied robust taxonomic assignment for more than 10 years.

Frustrated at this situation, an international group of researchers presents a search functionin the UNITE database for molecular identification of fungi. Its aim is to highlight the fungi we know the least about, and invite the scientific community to resolve their taxonomic affiliation. The effort seeks to bridge the substantial knowledge gap between fungal taxonomy and molecular ecology through a list, the authors refer to as the “50 Most Wanted Fungi”. Their work is presented in a new research paper published in the open-access journal MycoKeys.

Some 100,000 species of fungi have been described formally, although current estimates put the number of extant fungal species to at least 6 million. There is clearly no shortage of research venues in the study of fungi – but are there other shortages? The vast dark fungal diversity unravelled with molecular techniques hints that the interaction between fungal taxonomy and DNA sequencing of environmental substrates such as soil and water is not necessarily optimal.

“There is no taxonomic feedback loop in place to highlight the presence of these enigmatic lineages to the mycological community, and they often end up in sequence databases for years without attracting significant research interest,” explain the authors. “More than 10 years in some cases, as a matter of fact.”

Therefore, the researchers, led by Dr Henrik Nilsson, University of Gothenburg, now present a search function that produces lists of approximately genus-level clusters of fungal DNA sequences whose taxonomic affiliation we know next to nothing about. These lists are recomputed on a monthly basis, accounting for any updates and additions contributed by the scientific community in between each iteration. Community participation is encouraged, and the UNITE database has extensive support for third-party annotation.

By putting the spotlight on these fungal lineages, Dr Nilsson and colleagues hope to speed up the study and formal description of the underlying species. To support researchers focusing on select groups of fungi or environments, a set of keyword-filtered lists is provided. This allows researchers to zoom in on unknown fungi recovered, for example, from the built environment or aquatic habitats.

Commenting on their choice of a name for the list, the researchers clarify that the underlying fungi are not guilty of any crime. “Indeed, nothing can be said of the way they make a living. It is simply not known. We make no claim as to the importance of these fungi from whatever point of view – ecological, economic, or otherwise,” they stress. “We do make claim to their uniqueness, though, because it is frustrating, in the year 2016, not to be able to assign a name to a fungal sequence even at the phylum level.”

“We hope that the present publication will serve to put the spotlight on these uncharted parts of the fungal tree of life, and we invite the reader to examine them through our online tools or otherwise,” they conclude.

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Original source:

Nilsson RH, Wurzbacher C, Bahram M, Coimbra VRM, Larsson E, Tedersoo L, Eriksson J, Duarte Ritter C, Svantesson S, Sánchez-García M, Ryberg M, Kristiansson E, Abarenkov K (2016) Top 50 most wanted fungi. MycoKeys 12: 29-40. doi: 10.3897/mycokeys.12.7553