Seminar on Forest and Plant Health April 6th, 2022

1. Seminar on Forest and Plant Health
April 6th
, 2022
Natural Resources Institute Finland, Viikki, Helsinki
Strawberry plant with healthy leaves.
Mild powdery mildew symptoms with upward curling of leaflet margins and
sporulation. Photos: Tuuli Haikonen

2. Seminar on Forest and Plant Health, April 6th
, 2022
Natural Resources Institute Finland, Helsinki
Future biodiversity and ecosystem services levels given scenarios
of future land-use
Tord Snäll
Swedish University of Agricultural Sciences, Uppsala, Sweden
Email: Tord.Snall@slu.se
Global policy for future ecosystem services and biodiversity conservation is ultimately
implemented at landscape and local scales. In parallel, green infrastructure planning needs to
account for socioeconomic dynamics at national and global scales. Progress towards policy
goals must, in turn, be evaluated at the landscape scale. Moreover, to reach the Paris
Agreement, societies need to increase the global terrestrial carbon sink. There are many climate
change mitigation solutions (CCMS) for forests, including focusing on developing the
bioenergy, bioeconomy or protection. Bioenergy and bioeconomy solutions use climate-smart,
intensive management to generate high quantities of bioenergy and bioproducts. Protection of
(semi-)natural forests is a major component of ‘natural climate solution’ (NCS), since they
store carbon in standing biomass and soil.
I will present some of our work on investigating how ecosystem services and biodiversity may
respond to these external drivers and strategies. This includes evaluating three management
scenarios for a 100,000 hectare boreal forest landscape in the coming 100 years in terms of
their effects on the future habitat suitability/occupancy of four bird species, six wood-decaying
fungi and one lichen, most of them red-listed. Moreover, I will present joint impacts of CCMS
and different climate scenarios on future wood ES, non-wood ES, and regulating ES for
Sweden for 2020-2100.
The landscape-scale scenarios optimize financial returns and account for downscaled projected
global demand of wood given a middle-of-the road Shared Socioeconomic Pathway. We
contrast a reference scenario meeting the wood demand against an economy scenario with no
upper harvest limit, and a green infrastructure scenario optimizing the levels of environmental
indicators. In the green infrastructure scenario, the species increased the most, followed by the
reference scenario, and the economy scenario. All bird species increased in the green
infrastructure scenario, while in the other scenarios, future developments varied. Most fungi
increased in the production forest of the green infrastructure scenario but decreased in the
economy scenario. In all scenarios, the lichen Lobaria pulmonaria increased, owing to host
tree retention.
If time allows I will also go into our more detailed work on investigating the mechanisms
underlying the observed and simulated fungal and lichen colonization-extinction dynamics. I
will also show that in the long run, fulfilling the increased wood demand through bioenergy

3. and bioeconomy solutions will decrease future ES multifunctionality, but the increased tree
growth induced by rising greenhouse gas concentrations may partially offset these negative
effects. Adopting bioenergy and bioeconomy solutions will have a greater negative impact on
ES supply than adopting NCS. NCS can be considered an adaptation measure to offset negative
climate change effects on the future supplies of non-wood ES. Therefore, CCMS, with
increasing wood demand, will reduce forest ES multifunctionality but NCS has the potential to
cushion this negative impact, increasing the capacity of the forest to supply multiple ES in
synergy.
Further information
Belinchón R, Harrison PJ, Mair L, Várkonyi G, Snäll T (2017). Local epiphyte establishment
and future metapopulation dynamics in landscapes with different spatiotemporal
properties. Ecology 98: 741–750.
Henckel L, Bradter U, Jönsson M, Isaac NJB, Snäll T (2020). Assessing the usefulness of
Citizen Science Data for habitat suitability modelling: opportunistic reporting versus
sampling based on a systematic protocol. Diversity and Distributions 26: 1276–1290.1
Eggers J, Räty M, Öhman K, Snäll T (2020). How well do stakeholder-defined forest
management scenarios balance economic and ecological forest values? Forests 11: 86.
Mazziotta et al. In preparation. Increased future synergies and alleviated trade-offs between
forest ecosystem services under climate change mitigation solutions with more natural
climate solutions.
Moor H, Eggers J, Fabritius H, Forsell N, Henckel L, Bradter U, Mazziotta A, Nordén J,
Snäll T (2022). Rebuilding green infrastructure in boreal production forest given future
global wood demand. Journal of Applied Ecology in press.
Moor H, Nordén J, Penttilä J, Siitonen J, Snäll T (2021). Long-term effects of colonization-
extinction dynamics of generalist versus specialist wood-decaying fungi. Journal of
Ecology 109: 491–503.
1
The publisher Wiley has informed us that this is a ‘Top Cited Article 2020-2021’ in Diversity and
Distributions.

4. Seminar on Forest and Plant Health, April 6th
, 2022
Natural Resources Institute Finland, Helsinki
Could pine wood nematode (Bursaphelenchus xylophilus) cause
pine wilt disease or even establish inside healthy trees in Finland
now – or ever?
Juha Tuomola1
, Hannah Gruffudd2
, Kimmo Ruosteenoja3
and Salla Hannunen1
1
Finnish Food Authority, Mustialankatu 3, FI-00790 Helsinki
2
Forest Research Agency, Environment Centre Wales, Ffordd Deiniol, Bangor LL57 2UW,
UK
3
Weather and Climate Change Impact Research, Finnish Meteorological Institute, P.O. Box
503, FI-00101 Helsinki, Finland
Email: Juha.Tuomola@ruokavirasto.fi
Pine wood nematode (PWN, Bursaphelenchus xylophilus) is the causal agent of pine wilt
disease (PWD) that can, in suitable conditions, lead to mass mortality of susceptible trees. In
the EU, PWN is a quarantine pest for which all member states must conduct annual surveys
and take eradication measures if the pest is detected.
To support PWN risk management, we assessed the likelihoods of PWD and PWN
establishment inside susceptible healthy trees in Finnish present and future climate. The former
assessment was done using the mean summer temperature concept (MST) presented by
Gruffudd et al. (2016). For the latter assessment we defined easily usable annual growing
degree day (SDD) intervals for predicting the likelihood of PWN extinction and establishment
inside healthy trees. The intervals were defined using previously published results on modelling
of PWN population dynamics in Germany (Gruffudd et al. 2019). Both assessments were done
using 10 × 10 km resolution climate data from 2000–2019 and climate change projections for
2030–2080 prepared specifically for Finland under three Representative Concentration
Pathway (RCP) scenarios, RCP2.6, RCP4.5 and RCP8.5.
Our results suggest that the present Finnish climate is far too cool for PWD in healthy trees and
for the long-term establishment of PWN populations inside healthy trees. Furthermore, our
results indicate that the climate in Finland is likely to become suitable for PWD and PWN
establishment inside healthy trees by 2080 only if the worst-case RCP scenario (RCP8.5) is
realized. Consequently, our results imply that PWN might not deserve top priority in Finland
when allocating the limited resources for phytosanitary activities.

5. Further information
Gruffudd HR, Jenkins TAR, Evans HF (2016). Using an Evapo-Transpiration Model (ETpN)
to predict the risk and expression of symptoms of Pine Wilt Disease (PWD) across
Europe. Biological Invasions 18: 2823–2840. https://doi.org/10.1007/s10530-016-1173-7
Gruffudd HR, Schröder T, Jenkins TAR, Evans HF (2019). Modelling Pine Wilt Disease
(PWD) for Current and Future Climate Scenarios as Part of a Pest Risk Analysis for Pine
Wood Nematode Bursaphelenchus xylophilus (Steiner and Buhrer) Nickle in Germany.
Journal of Plant Diseases and Protection 126: 129–144. https://doi.org/10.1007/s41348-
018-0197-x
Tuomola J, Gruffudd H, Ruosteenoja K, Hannunen S (2021). Could Pine Wood Nematode
(Bursaphelenchus xylophilus) Cause Pine Wilt Disease or Even Establish inside Healthy
Trees in Finland Now—Or Ever? Forests 12(12): 1679.
https://doi.org/10.3390/f12121679

6. Seminar on Forest and Plant Health, April 6th
, 2022
Natural Resources Institute Finland, Helsinki
Survey programmes and contingency plans for forest pests
Liisa Vihervuori
Finnish Food Authority, Mustialankatu 3, FI-00790 Helsinki
Email: Liisa.Vihervuori@ruokavirasto.fi
In the European Union, Survey programmes for forest pests started in 2015. In Finland, 2016.
Their aim is to prohibit spreading of quarantine pests to EU. Multiannual survey programmes
and annual surveys of each priority pest shall be carried out. Priority pests include several forest
(tree) pests: Agrilus anxius and A. planipennis, Anoplophora glabripennis and chinensis,
Bursaphelencus xylophilus and Dendrolimus sibiricus. Each member state shall draw up and
keep up to date a contingency plan for each priority pest capable of entering and becoming
established in its territory.
The non-annual surveyed forest pests include quarantine species, for example: Polygraphus
proximus, Monochamus spp. (as vector for B. xylophilus), non-European Pissodes and
Atropellis pinicola and A. piniphila.
Recently, A. planipennis has been found in Moscow and in St. Petersburg. After the two
separate outbreak spots in St. Petersburg were found in 2020, we started intensive survey in
southern Finland. About 20 traps were installed to host trees (Fraxinus sp., Juglans sp. and
Pterocarya sp.) in risky sites such as parks and seaport areas. If an official positive finding will
be found less than 100 kilometres from the EU border, official procedures including moving
ban of host plants and wood will begin in this buffer area.

7. Seminar on Forest and Plant Health, April 6th
, 2022
Natural Resources Institute Finland, Helsinki
Two types of resistance against a major wheat disease Septoria
Tritici Blotch
Petteri Karisto
Natural Resources Institute Finland (Luke), Tietotie 4, FI-31600 Jokioinen, Finland
Email: petteri.karisto@luke.fi
Septoria tritici blotch (STB) caused by fungus Zymoseptoria tritici is a major disease of wheat
in Europe. Breeding for quantitative resistance promises to lead to more durable disease control
but is limited by difficulties in measuring quantitative differences between cultivars in a
reproducible manner. We used automated image analysis on a collection of 21 420 leaves from
335 elite European winter wheat cultivars naturally infected by a diverse local population of Z.
tritici. We obtained precise, objective and reproducible quantitative measures of conditional
STB intensity that allowed us to separate resistance affecting host damage from resistance
affecting pathogen reproduction. The cultivar rankings differed between the two measures,
indicating that the two types of resistance should be considered separately in breeding
programs. The different forms of resistance are under separate genetic control, enabling them
to be recombined to form new cultivars that are highly resistant to STB. We showed that
measures of pathogen reproduction early in the season were the best predictors of host damage
late in the season, illustrating the importance of breeding for resistance against pathogen
reproduction in order to suppress epidemics and minimize yield losses caused by STB. These
data can already be used by breeding programs to choose wheat cultivars that are broadly
resistant to naturally diverse Z. tritici populations according to the different classes of
resistance.
Further information
Karisto P, Hund A, Yu K, Anderegg J, Walter A, Mascher F, McDonald BA, Mikaberidze A
(2018). Ranking quantitative resistance to Septoria Tritici Blotch in elite wheat cultivars
using automated image analysis. Phytopathology 108: 568–581.
https://doi.org/10.1094/PHYTO-04-17-0163-R
Yates S, Mikaberidze A, Krattinger SG, Abrouk M, Hund A, Yu K, Studer B, Fouche S,
Meile L, Pereira D, Karisto P, McDonald BA (2019). Precision phenotyping reveals novel
loci for quantitative resistance to Septoria Tritici Blotch. Plant Phenomics: 3285904.
https://doi.org/10.34133/2019/3285904

8. Seminar on Forest and Plant Health, April 6th
, 2022
Natural Resources Institute Finland, Helsinki
Disease resistances from strawberry pre-breeding materials:
case powdery mildew
Tuuli Haikonen1
, Attiq Rehman1
, Marja Rantanen2
and Saila Karhu3
1
Natural Resources Institute Finland (Luke), Toivonlinnantie 518, FI-21500 Piikkiö, Finland
2
Natural Resources Institute Finland (Luke), Survontie 9, FI-40500 Jyväskylä, Finland
3
Natural Resources Institute Finland (Luke), Itäinen Pitkäkatu 4 A, FI-20520, Turku, Finland
Email: tuuli.haikonen@luke.fi
Production of our most important berry crop, garden strawberry (Fragaria×ananassa), is
challenged by stresses brought by climate change. At the same time, political and societal
awareness of environmental footprint of food production increases. New non-chemical means
of crop protection are better effective in such cultivars that have resistances to pests or
pathogens.
One of the economically most important diseases of strawberry, the leaf and fruit disease
powdery mildew (caused by Podosphaera aphanis) thrives in relatively dry conditions with
short leaf wetness duration. Many of our main cultivars are susceptible and regular applications
of pesticides are already required. Improving resistance in strawberry in traditional breeding is
difficult due to complex genetics and low variation of the trait. Hence, finding resistances from
new sources and developing genome-informed selection tools will improve substantially
breeding efforts for this trait.
In this work we have inspected resistances to powdery mildew and to other fungal leaf diseases
in a unique pre-breeding material. A population of re-constructed garden strawberry was
created by hybridization of selected accessions of its wild ancestor species, F. chiloensis and
F. virginiana, to introduce high underutilized diversity, prominent vigour, disease resistances
and resilience. The population with over 300 individuals has been SNP genotyped using a
strawberry 50K SNP array and established a replicated field trial from clonally propagated
materials. The severity of powdery mildew symptoms was recorded using Simpson’s scale with
time series observations during two growing seasons. Statistical analyses and genome-wide
association study were applied to discover genomic regions associated with resistances. Our
final aim is to accelerate strawberry breeding by informed selection of optimal alleles required
for healthy productive crop.

9. Seminar on Forest and Plant Health, April 6th
, 2022
Natural Resources Institute Finland, Helsinki
Intercropping, a potential countermove against ecosystem service
degradation in agricultural landscapes
Ari Järvinen
Natural Resources Institute Finland (Luke), Survontie 9, FI-40500 Jyväskylä, Finland
Email: ext.ari.jarvinen@luke.fi
The study explored cropping system diversification impacts on natural biological control and
pollination. The aim was to improve cropping system’s ecological sustainability and to reduce
reliance on external chemical inputs.
Two-year field experiment was conducted to study strip intercropping of two mass-flowering
crops: spring turnip rape and faba bean. Selected crops indicated complementary nutrient use
and ability to offer wide range of supplementary resources for beneficial arthropods. More pest-
prone turnip rape is a superb nectar source, while earlier faba bean facilitates nitrogen economy
and provides extrafloral nectar, for example.
The experimental setup consisted of three parallel 100 × 50 m treatments in five separate fields.
The treatments were pure stands of spring turnip rape and faba bean and intercropping of both
crop species in 5 meters wide strips. Beneficial insects were sampled with transect walks, pan
traps, and pit traps. The data was analysed with generalized linear mixed models in R.
Arthropod abundance, species richness, species diversity, and sample similarity were assessed.
Strip intercropping resulted in a characteristic pollinator assemblage and retained common
specialist pollinators of both crops. Pollinator abundance and species diversity increased with
the mass flowering progress. Unexpectedly, turnip rape monoculture attracted the most diverse
pollinator pool.
The total abundance and species diversity of arthropod predators were not significantly affected
by intercropping. The pest abundance followed host proportion, however, which improved
predator to prey ratio of intercropping treatment. The abundance of both predators and pests
decreased with sampling progress.
This study is a part of the project “Crop diversification and intercropping for ecological
intensification: maximizing natural biological control and pollination (LUMOTTU)” funded
by Finnish Cultural Foundation.

10. Seminar on Forest and Plant Health, April 6th
, 2022
Natural Resources Institute Finland, Helsinki
New observations on the viruses HetPV13-an1 and HetPV15-pa1
in Heterobasidion annosum host strains
Elina Roininen, Tuula Piri, Eeva Vainio and Jarkko Hantula
Natural Resources Institute Finland (Luke), Latokartanonkaari 9, FI-00790 Helsinki, Finland
Email: ext.elina.roininen@luke.fi
Transmission experiments with the partitiviruses HetPV13-an1 and HetPV15-pa1 and
Heterobasidion ourmia-like-virus from different donors to altogether 15 Finnish
Heterobasidion annosum strains were conducted. Virus combination of donors and genotypes
of donor and recipient affected transmission frequency.
Growth experiment on agar plates was done to test phenotypic effects of HetPV15-pa1 and
coinfection of HetPV13-an1 and HetPV15-pa1. The growth of three H. annosum genotypes
was accelerated by viruses, and three genotypes showed no effects. Later, the growth of four
H. annosum genotypes was tested in billets, and no differences were detected in the growth
between virus infected and virus free strains.
In an in vivo experiment, HetPV13-an1 increased the efficacy of Phlebiopsis gigantea in pine
roots systems in restricting the growth of H. annosum. This suggests that the effects of these
viruses might become visible only in natural conditions.

11. Seminar on Forest and Plant Health, April 6th
, 2022
Natural Resources Institute Finland, Helsinki
Bacteria biota of Heterobasidion fruiting body and associated
decayed wood
Wenzi Ren1
, Reijo Penttilä2
, Risto Kasanen1
, Fred O. Asiegbu1
1
Department of Forest Sciences, University of Helsinki, Helsinki, Finland
2
Natural Resources Institute Finland (Luke), Helsinki, Finland
Email: wenzi.ren@helsinki.fi
The species Heterobasidion annosum and H. parviporum are causal agents of the most severe
root and stem rot disease of conifer trees with estimated annual economic loss of 800 million
euros in Europe. Despite extensive research on the genetics and infection biology, very little is
however known of the microbiome inhabiting its fruiting body. An understanding of the
fruiting body bacteria biota could provide insight on the crucial functional roles they play in
the sporocarp growth, nutrition, development and other metabolic processes, such as adaption
to the environment and even pathogenesis. In this study, using next generation sequencing of
the 16S region, we investigated the bacteria biota of the Heterobasidion fruiting body and its
adhering deadwood. There was a total of 7,462 OTUs found in both materials, and an average
of 52.6% of bacteria biota in fruiting body were shared with the associated dead wood. The
overall and unique OTUs had decreasing trend from decay classes one to three but increasing
in decay class four. Fruiting body had the comparable OTU numbers at the beginning and the
end of the decay, while wood had 50% less OTU numbers in the decay class four compared to
decay class one. The bacteria genera Burkholderia, Sphingomonas, and Pseudommonas were
more abundant in the fruiting body and the phylum Firmicutes was more dominant in wood
tissue. FAPROTAX functional structure analysis revealed the differentiation between the two
materials happened in the third decay class. Our results also showed that bacteria communities
in both substrates experienced a process of a new community re-construction with progress of
decay. The bacteria community was highly dynamic, the microbiota activeness, community
stability, and functions changed with the decay process. The third decay class was an important
turning point for community re-structuring, physical-chemical changes of fruiting body and
wood probably had strong effects. Bacteria community in fruiting body attached to the living
standing tree was suppressed compared to those associated with dead wood. Bacteria appear to
spread from wood tissue of standing living tree to fruiting body, but after the tree is killed,
bacteria moved from fruiting body to wood. Bacteria inhabiting fruiting body and wood has
diverse functions, they could be beneficial, harmful or opportunistic, most likely environmental
factors and community structure jointly influence the result. Future studies may wish to
investigate if the fruiting body microbiome have the ability to enrich their host genome with
complementary functional genes which could help to improve the utilization of nutrients that
are lacking on the hosts and result to shift in the ecology and community assembly of the
species.

12. Seminar on Forest and Plant Health, April 6th
, 2022
Natural Resources Institute Finland, Helsinki
The dark septate endophyte suppresses conifer pathogen
transcripts and promotes root growth of Norway spruce in a
tripartite interaction
Kai Wang, Zilan Wen, Fred O Asiegbu
Faculty of Agriculture and Forestry, Department of Forest Sciences, University of Helsinki,
Finland
Email: kai.wang@helsinki.fi
Plant associated microbes play multiple functional roles in host fitness. Dark septate
endophytes (DSE) offer growth promotion and increased defence to forest trees. However, the
impact of the interaction on DSE transcriptome and metabolites during tripartite interaction
with host and pathogen is unknown. To reveal the tripartite interaction, seedlings of Norway
spruce were infected with DSE Phialocephala sphaeroides, or with conifer root rot pathogen
Heterobasidion parviporum, or with both. DSE showed lower but stable mapped transcripts in
tripartite system, while H. parviporum transcripts reduced largely. From RNAseq analysis,
DSE experienced a shift from cell growth to anti-stress and antagonistic responses, and it
repressed H. parviporum to access certain carbohydrate nutrients. The expression of genes
encoding plant growth promotion products were detected in both DSE and pathogen, which
was further supported by production of tryptophan-dependent indolic compounds in DSE
culture. DSE culture filtrate treatment exhibited enhanced Arabidopsis root hairs and spruce
primary root elongation. Taken together, these results exhibited that the endophyte had strong
repressive effect on pathogen H. parviporum in a tripartite interaction with host Norway spruce.

13. Seminar on Forest and Plant Health, April 6th
, 2022
Natural Resources Institute Finland, Helsinki
Norway spruce inoculated with Heterobasidion parviporum:
impact of different alleles in spruce root rot resistance locus
(PaLAR3)
Eeva Terhonen, Kashif Muhammad, Tuula Piri, Neea Hanström, Tuija Hytönen, Katri Leino,
Jarkko Hantula
Natural Resources Institute Finland (Luke), Latokartanonkaari 9, FI-00790 Helsinki, Finland.
Email: eeva.terhonen@luke.fi
Locus PaLAR3 has suggested to be a root rot resistance marker for Norway spruce (Picea
abies). PaLAR3 encodes leucoanthocyanidin reductase. Higher resistance in Norway spruce
against Heterobasidion parviporum was noted to associate when the rare allele B was found in
PaLAR3. In this study, we tested the spread of H. parviporum through root contacts in the field.
The aim was to see if trees with B-allele in PaLAR3 gene can resist the infection. Altogether,
72 10-year-old trees were cut down and the stumps were inoculated with mixture (four strains)
of H. parviporum. After three years the closest trees were cut down and the stumps collected.
After incubation in room temperature for 10 days the stumps were microscoped and infection
confirmed based on conidiospores. Forty percent (40%) of the trees were infected with H.
parviporum. B-allele was found to be rare (AB-allele combination 29% and BB-allele
combination 1%) There were no statistical backup found that certain allele could prevent the
infection (AA, AB and BB equally infected). Similarly, the distance from inoculated stump or
the diameter of the tree did not have impact for the infection to occur. Supporting results were
found from necrosis experiment, where 3-year-old trees were infected with two different H.
parviporum strains.