Invasive Phytophthora species affecting broadleaved tree species in urban and landscape settings in Southern Sweden

Phytophthora translates to ‘plant destroyer’ and are fungal-like, hemibiotrophic plant pathogens. Phytophthora was discovered in the mid 19th century, as the causal agent of the widespread collapse of potato crops throughout Europe. Today, more than 150 Phytophthora species have been identified and they continue to cause massive problems, both in agriculture and forest ecosystems. There are many Phytophthoras species responsible for dramatic forest diebacks. In Europe, Phytophthoras are casual agents of oak decline, ink disease of chestnut, beech decline and dieback of alders. The aim of this study was to examine which forest Phytophthora species are present in southern Sweden. Symptomatic trees were identified in five urban forest settings in Southern Skåne. Stem tissue and soil surrounding symptomatic trees were collected. Phytophthora isolates were cultured on artificial media and their DNA sequenced by sanger-­sequencing. The obtained sequences were compared with the known reference sequences using the basic local alignment search tool (BLAST) at NCBI. Five Phytophthora species were identified: P. cactorum, P. cambivora, P. gonapodyides, P. plurivora and P. syringae. The result includes the first findings of P. gonapodyides causing stem lesions on trees in Sweden. Confirmation of pathogenicity of P. gonapodyides in an inoculation trial using obtained P. gonapodyides isolates confirmed that they were able to infect healthy beech seedlings, resulting in stem lesions. Many common tree species in Southern Sweden are susceptible to the Phytophthora species found in this study. Trade with nursery seedlings is an important pathway of dispersal and establishment of Phytophthoras in natural environments. There is no efficient treatment and it is practically impossible to eradicate Phytophthora once it has become established in a site. If the identified Phytophthora species become widely established in Sweden, they may cause severe damages to forest ecosystems as well as for the Swedish forestry sector

Mosstäcket ökar tillväxten hos Vaccinium myrtillus

Tillväxten i boreala skogsekosystem är kvävebegränsad. Tidigare studier har visat att mosstäcket i dessa ekosystem har en positiv inverkan på näringsstatus hos ljungväxter. Detta har förklarats med mosstäckets höga förmåga att ansamla näringsämnen och att ljungväxters ytliga rotsytem med erikoid mykorrhiza kan ackumulera organiska näringsämnen som frigörs från mosstäcket. Vi undersökte hur tillväxten hos Vaccinium myrtillus påverkas av ett mosstäcke dominerat av Pleurozium schreberi och hur tillväxten hos dessa arter påverkas av kvävetillförsel. Fältförsöket genomfördes 1998-2000 med följande behandlingar: kontroll, borttaget mosstäcke, intakt mosstäcke, borttaget mosstäcke +gödsel, intakt mosstäcke +gödsel. Kvävetillförseln motsvarade 10 kg N ha-1 år-1. För att bestämma tillväxten hos V. myrtillus insamlades årsskott där torrvikt, längd och bladantal bestämdes, för insamlade skott av P. schreberi bestämdes endast torrvikt. Ett intakt mosstäcke ökade tillväxten hos V. myrtillus då alla uppmätta variabler hos årsskotten påverkades positivt. Både V. myrtillus och P. schreberi ökade sin tillväxt vid kvävetillförsel, vilket visar på en kvävebegränsad tillväxt hos dessa arter. Det fanns ingen signifikant interaktion mellan mosstäckets och gödslingens positiva effekter på tillväxten hos V. myrtillus. Våra resultat tyder på att V. myrtillus, via sin erikoida mykorrhiza, har tillgång till näringsämnen som frigörs från mosstäcket.The growth in boreal forest ecosystem is nitrogen limited. Previous studies have shown that the moss layers in these ecosystems have a positive impact on the nutritional status of dwarf shrubs. This has been explained by the high bility of the moss layer to accumulate nutrients, and that dwarf shrubs shallow roots with ericoid mycorrhiza have the ability to utilize organic nutrients released from the moss layer. We examined how a moss layer dominated by Pleurozium schreberi affects the growth of Vaccinium myrtillus and how the growth of these species is affected by nitrogen supply. The field experiment was conducted 1998-2000 with the following treatments: control, removed moss layer, intact moss layer, removed moss layer+fertilization, intact moss layer+fertilization. The nitrogen supply corresponded to 10 kg N ha-1 yr-1. To determine the growth of V. myrtillus the annual shoots were collected and the dry weight, length and number of leaves was determined, while only the dry weight was determined for the shoots of P. schreberi. An intact moss layer increased the growth of V. myrtillus since all the measured variables of the annual shoots were positively affected. Both V. myrtillus and P. schreberi increased their growth due to the nitrogen addition, indicating a nitrogen-limited growth in these species. There was no significant interaction between the positive impacts of the moss layer and fertilization. Our results suggest that V. myrtillus, through its ericoid mycorrhiza, have access to nutrients released from the moss layer

Oomycetes in rhizosphere soil of ornamental plants from retail nurseries in Southern Sweden

Trade of herbaceous and woody ornamental plants is recognized as a principal pathway for the introduction of alien plant pathogens, such as soil-borne Phytophthora and Pythium species (oomycetes). The rhizosphere soil of container-grown plants obtained from 13 nurseries and garden centres in southern Sweden were sampled and the presence of Phytophthora and Pythium species determined using traditional baiting and isolation. DNA sequencing of isolates revealed five Phytophthora taxa including P. cinnamomi, P. citricola s.l., P. plurivora, P. undulata and a non-identified Phytophthora sp., as well as Phytopythium cf. citrinum and several species of Pythium. Phytophthora cinnamomi was detected on two different ornamental plants at the same nursery and is a first record of P. cinnamomi in Sweden. The survey revealed that a diversity of potentially pathogenic oomycetes is associated with ornamental plants available for sale in Sweden and emphasizes the need to recognize potential risks if these organisms get introduced in nature

Oomycete Soil Diversity Associated with Betula and Alnus in Forests and Urban Settings in the Nordic-Baltic Region

For about 25 years, forest managers in Sweden have been treating stumps following harvesting with Phlebiopsis gigantea, retailed as Rotstop®S gel, against spore infections of Heterobasidion, which cause root rot in order to minimize losses in timber production. However, not all forest managers trust the efficacy of stump treatment and this fact has hindered widespread adoption of stump treatment using P. gigantea. In this study, we evaluated stump treatment in the field during commercial thinning operations across 15 sites, by assessing the degree of stump coverage and subsequent infection levels in stump discs. In total, 45 % of all stumps were infected with Heterobasidion spp.. Nineteen percent of all stumps were considered to have full (100 %) coverage by Rotstop®S but contractors failed to achieve the manufacturers stipulated minimum coverage (85 %) in approximately 1/3 of all stumps. Using PCR, we could only detect the presence of P. gigantea in 73 % of the tested stumps. Large variation occurred between stump coverage and the recovery of P. gigantea in wood chip samples collected from stump discs across sites. In the worst case, we detected P. gigantea in only three out of ten treated stumps at one site. Despite this discrepancy we saw a clear reduction of the size of Heterobasidion infections on stumps where stump treatment coverage was more than 85 % of the stump surface.Our results suggest that forest operators in Sweden repeatedly fail to either apply a spore solution of P. gigantea or cover enough of the stumps to provide the desired protection. The outcome of such sub-standard application, could further undermine the usage of biological control agents in forestry and limit any potential control against Heterobasidion spp.

The digitalisation of the Nordic bioeconomy and its effect on gender equality

With digitalisation, the male-dominated bioeconomy sector becomes intertwined with the male-dominated tech sector. We focus on the effects on gender equality within the bioeconomy sector when these two gender unequal sectors are merged. We review the existing literature by studying three concepts - bioeconomy, digitalisation and gender - as a way to highlight the current state of knowledge on gender in the Nordic digitalised bioeconomy. Through this investigation we provide directions for future research and suggest actions to be taken. The contemporary literature discusses two major areas of focus: the impact of history on today's situation and gender inequality as a women's issue. We propose four areas of future research focus: moving beyond a historical perspective, understanding the effectiveness of women-only activities, focusing on men's role in gender equality work, and developing sustainability. We identify four points of action for practitioners in the literature: female role models, mentorship programmes, networks for young professionals and students and incorporating gender into bioeconomy-related education. However, together with the proposed future research, we suggest two considerations when practitioners in the Nordic digitalised bioeconomy take action: being mindful of the purpose and structure of women-only activities and including men when working with gender issues

The potential of biological control against Heterobasidion root rot is not realized in practical forestry

For about 25 years, forest managers in Sweden have been treating stumps following harvesting with Phlebiopsis gigantea, retailed as Rotstop (R) S gel, against spore infections of Heterobasidion, which cause root rot in order to minimize losses in timber production. However, not all forest managers trust the efficacy of stump treatment and this fact has hindered widespread adoption of stump treatment using P. gigantea. In this study, we evaluated stump treatment in the field during commercial thinning operations across 15 sites, by assessing the degree of stump coverage and subsequent infection levels in stump discs. In total, 45 % of all stumps were infected with Heterobasidion spp.. Nineteen percent of all stumps were considered to have full (100 %) coverage by Rotstop (R) S but contractors failed to achieve the manufacturers stipulated minimum coverage (85 %) in approximately 1/3 of all stumps. Using PCR, we could only detect the presence of P. gigantea in 73 % of the tested stumps. Large variation occurred between stump coverage and the recovery of P. gigantea in wood chip samples collected from stump discs across sites. In the worst case, we detected P. gigantea in only three out of ten treated stumps at one site. Despite this discrepancy we saw a clear reduction of the size of Heterobasidion infections on stumps where stump treatment coverage was more than 85 % of the stump surface.Our results suggest that forest operators in Sweden repeatedly fail to either apply a spore solution of P. gigantea or cover enough of the stumps to provide the desired protection. The outcome of such sub-standard application, could further undermine the usage of biological control agents in forestry and limit any potential control against Heterobasidion spp.

Oomycetes in rhizosphere soil of ornamental plants from retail nurseries in Southern Sweden

Trade of herbaceous and woody ornamental plants is recognized as a principal pathway for the introduction of alien plant pathogens, such as soil-borne Phytophthora and Pythium species (oomycetes). The rhizosphere soil of container-grown plants obtained from 13 nurseries and garden centres in southern Sweden were sampled and the presence of Phytophthora and Pythium species determined using traditional baiting and isolation. DNA sequencing of isolates revealed five Phytophthora taxa including P. cinnamomi, P. citricola s.l., P. plurivora, P. undulata and a non-identified Phytophthora sp., as well as Phytopythium cf. citrinum and several species of Pythium. Phytophthora cinnamomi was detected on two different ornamental plants at the same nursery and is a first record of P. cinnamomi in Sweden. The survey revealed that a diversity of potentially pathogenic oomycetes is associated with ornamental plants available for sale in Sweden and emphasizes the need to recognize potential risks if these organisms get introduced in nature

Oomycete Soil Diversity Associated with <i>Betula</i> and <i>Alnus</i> in Forests and Urban Settings in the Nordic–Baltic Region

This study aimed to determine the differences and drivers of oomycete diversity and community composition in alder- and birch-dominated park and natural forest soils of the Fennoscandian and Baltic countries of Estonia, Finland, Lithuania, Norway, and Sweden. For this, we sequenced libraries of PCR products generated from the DNA of 111 soil samples collected across a climate gradient using oomycete-specific primers on a PacBio high-throughput sequencing platform. We found that oomycete communities are most affected by temperature seasonality, annual mean temperature, and mean temperature of the warmest quarter. Differences in composition were partly explained by the higher diversity of Saprolegniales in Sweden and Norway, as both total oomycete and Saprolegniales richness decreased significantly at higher longitudes, potentially indicating the preference of this group of oomycetes for a more temperate maritime climate. None of the evaluated climatic variables significantly affected the richness of Pythiales or Peronosporales. Interestingly, the relative abundance and richness of Pythiales was higher at urban sites compared to forest sites, whereas the opposite was true for Saprolegniales. Additionally, this is the first report of Phytophthora gallica and P. plurivora in Estonia. Our results indicate that the composition of oomycetes in soils is strongly influenced by climatic factors, and, therefore, changes in climate conditions associated with global warming may have the potential to significantly alter the distribution range of these microbes, which comprise many important pathogens of plants