Tuula Piri

Tuula Piri
Finnish Forest Research Institute | METLA · Vantaa Unit

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52
Publications
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Publications

Publications (52)
Article
Full-text available
Utilizing Heterobasidion partitivirus 13 strain an1 (HetPV13-an1) and 15 strain pa1 (HetPV15-pa1) in co-infection is considered a potential biocontrol approach against Heterobasidion root and butt rot. Both parti-tiviruses mediate debilitating effects in most Heterobasidion host isolates and are generally transmitted efficiently between host strain...
Article
Full-text available
Heterobasidion parviporum is a fungal pathogen that is drastically damaging Norway spruce ( Picea abies ) in Europe. The infections will result in root and stem rot, causing significant economic losses for forest owners. Previous studies have shown that the PaLAR3 gene, which encodes the leucoanthocyanidin reductase enzyme, can increase resistance...
Article
The combined use of Heterobasidion partitiviruses 13 and 15 (HetPV13-an1 and HetPV15-pa1) is considered a promising biocontrol approach against Heterobasidion root and butt rot. In a previous study, the transmission frequency of HetPV15-pa1 was found to be higher from a double partitivirus-infected donor than from a single partitivirus-infected don...
Article
Full-text available
Treatment of conifer stumps with a control agent effectively prevents Heterobasidion spore infections in summer cuttings and protects the residual stand and the next tree generation from damage caused by Heterobasidion root rot. Thus far, stump treatment experiments have been carried out in mineral soils, and no information is available on the effi...
Article
Full-text available
The most destructive root rot pathogen of Norway spruce (Picea abies) in Finland is Heterobasidion parviporum. After primary infection, this pathogen spreads from tree to tree through root contacts and eventually causes high levels of root and stem rot. Locus PaLAR3 has been associated with root rot resistance of Norway spruce, and higher resistanc...
Article
Full-text available
According to several earlier studies, the prevalence of Heterobasidion in peat soils is generally lower compared to mineral soils. However, in some Norway spruce (Picea abies (L.) Karst.) stands on drained peat soils in Latvia, serious damage caused by Heterobasidion root rot has been observed. To determine the spread of Heterobasidion spp. on peat...
Article
Full-text available
Heterobasidion species are highly destructive basidiomycetous conifer pathogens of the Boreal forest region. Earlier studies have revealed dsRNA virus infections of families Curvulaviridae and Partitiviridae in Heterobasidion strains, and small RNA deep sequencing has also identified infections of Mitoviridae members in these fungi. In this study,...
Article
Full-text available
This study provides new information on the infection biology and pathogenicity of an important root-rot fungus, Heterobasidion annosum sensu stricto (Fr.) Bref., through a detailed examination of the vegetative spread of clonal individuals and their capacity to produce fruiting bodies on young pine seedlings. The seedlings were planted in a clear-c...
Article
Full-text available
Root rot, caused by the decay fungus Heterobasidion annosum, damages both below- and above-ground parts of Scots pines (Pinus Sylvestris L.). The diseased pines are often first characterized by deteriorated crowns and they will eventually be killed by the infection, but the process is gradual and difficult to be observed before the symptoms are sev...
Article
Because intensive forestry favors the spread of Heterobasidion spp., increasing amounts of decayed Norway spruce (Picea abies) wood in forest stands should be taken into account in the management of commercial forests. Spruce wood colonized by Heterobasidion spp. ensures fruit body formation, which increases the risk of new infections by basidiospo...
Article
Full-text available
Afforestation of former agricultural lands is a common practice in several countries. This is beneficial for avoiding diseases carry-over from previous forest generations and to expand forest areas. However, several biotic and abiotic risks have been reported in such stands, including a higher risk of Heterobasidion root rot after thinning. Therefo...
Article
Full-text available
: Afforestation of former agricultural lands is a well-established practice in several countries. It is beneficial for avoiding previous-generation forest diseases and expanding forest areas. However, several biotic and abiotic risks have been reported for such stands as well as a higher risk of Heterobasidion root rot after thinning. Therefore, th...
Article
Full-text available
The boreal forests of Fennoscandia are largely dominated by Norway spruce and Scots pine. Conifer monocultures have been favoured in forest management during the last decades. Recently, concern has risen that forests consisting of only one tree species could be vulnerable to biotic damage. Additionally, environmental and societal changes are placin...
Article
Full-text available
Treatment of freshly cut stumps with biological control agents containing Phlebiopsis gigantea spores effectively restricts the spread of new Heterobasidion infections in conifer forests. To test the control efficacy of different P. gigantea strains, conifer stumps or billets cut from tree stems can be artificially infected with asexual Heterobasid...
Article
Although impacts of intensive forest harvesting practices such as removing logging residue and stumps for bioenergy on forest ecosystem has been extensively studied, no information is available about the long-term effects of stump harvesting on the health status of young Norway spruce stands. In the present study, we surveyed damage caused by the l...
Article
Full-text available
Heterobasidion spp. cause economically important losses in conifer forests in the Northern Hemisphere, especially in Norway spruce stands. Freshly cut stumps are the main route for Heterobasidion spp. infection. Even small stumps of spruce seedlings are known to be susceptible to spore infection, however, very little is currently known about the su...
Article
The financial incentives to perform stump treatment against root and butt rot caused by fungal agent Heterobasidion annosum were analyzed by simulating multiple scenarios of primary and secondary infection rates in southern and central Finland. Forest dynamics of two Norway spruce (Picea abies) dominated stands were simulated with MOTTI and Hmodel...
Article
Full-text available
We investigated the diversity and spatial distribution of viruses infecting strains of the root rot fungus Heterobasidion annosum collected from pine stumps at a heavily infected forest site. Four different partitiviruses were detected in 14 H. annosum isolates at the study site, constituting approximately 29% of all Heterobasidion isolates investi...
Article
Full-text available
The fungal genus Heterobasidion includes some of the most devastating conifer pathogens in the boreal forest region. In this study, we showed that the alphapartitivirus Heterobasidion partitivirus 13 from Heterobasidion annosum (HetPV13-an1) is the main causal agent of severe phenotypic debilitation in the host fungus. Based on RNA sequencing using...
Article
We tested if root colonisation by ectomycorrhizal fungi (EMF) could alter the susceptibility of Norway spruce (Picea abies) seedlings to root rot infection or necrotic foliar pathogens. Firstly, spruce seedlings were inoculated by various EMF and challenged with Heterobasidion isolates in triaxenix tubes. The ascomycete EMF Meliniomyces bicolor, th...
Article
The Heterobasidion annosum species complex is a widely distributed group of fungal conifer pathogens causing root and butt rots. We studied the key processes of Heterobasidion epidemiology by compiling models that rely on biological processes. Models were included in the mechanistic model with stochastic elements, Hmodel, simulating the fungal dyna...
Conference Paper
Full-text available
Heterobasidion annosum viruses may disperse along with fungal hosts through the root systems to neighboring trees and next generation seedlings. Here, we describe the presence of viruses and their transmission frequencies in a fungal-infected pine forest site in southern Finland. In five fungal clones of the site, nearly 19% of H. annosum isolates...
Article
In boreal forests, stumps of Norway spruce are removed after clear cutting to gather wood for energy and, additionally, to reduce damage caused by the root rot fungus, Heterobasidion parviporum. In order to understand the behavior of H. parviporum at stump-harvested Norway spruce sites, the survival of Heterobasidion mycelia in buried root fragment...
Article
Fungal viruses (mycoviruses) with RNA genomes are believed to lack extracellular infective particles. These viruses are transmitted laterally among fungal strains through mycelial anastomoses or vertically via their infected spores, but little is known regarding their prevalence and patterns of dispersal under natural conditions. Here, we examined,...
Article
Full-text available
Heterobasidion annosum (Fr.) Bref. s.l., a group of fungi causing root rot, is a serious threat to Norway spruce (Picea abies (L.) Karst.) stands in northern Europe. A new stochastic spatial model (Hmodel) was developed to simulate H.annosum s.l. infection and spread within a stand. Hmodel was combined with the stand-level decision support system M...
Article
Full-text available
Notwithstanding Norway spruce (Picea abies (L.) Karst.) is highly prone to root rot caused by Heterobasidion parviporum Niemelä & Korhonen, but little is known about the epidemiology of Heterobasidion root rot in spruce stands applied to uneven-aged management. To get insight into the development of Heterobasidion infections in this type of forest,...
Article
We investigated the effects of two recently described dsRNA mycoviruses, HetRV3-ec1 and HetRV6-ab6, on Heterobasidion wood decay fungi. The viruses originally inhabited Heterobasidion ecrustosum and Heterobasidion abietinum, and were transferred in the laboratory into other Heterobasidion species. Isogenic virus-free and virus-infected Heterobasidi...
Article
Full-text available
Viruses infecting the conifer pathogenic fungus Heterobasidion annosum sensu lato are intracellular and spread via anastomosis contacts. In the laboratory, these viruses transmit readily even between somatically incompatible isolates, but their dispersal capacity in natural conditions has not been previously studied. We introduced a mycovirus to a...
Article
We describe a novel putative mycovirus infecting the conifer root-rot fungus Heterobasidion annosum sensu lato. This virus, designated as Heterobasidion RNA virus 6 (HetRV6), is taxonomically distant from all previously known viruses of Heterobasidion species, but somewhat related to the Curvularia thermal tolerance virus and the Fusarium graminear...
Article
The incidence of Heterobasidion root rot in the advance regeneration of Norway spruce (Picea abies (L.) Karst.) was studied in nine stands at four different localities in southern Finland. The mean age of the unthinned advance regeneration on the 17 sample plots ranged from 14 to 44 years. On infested plots, the proportion of Norway spruce infected...
Article
Full-text available
Root rot infections in Norway spruce (Picea abies (L.) Karst.) regeneration, planted after the clear-cutting of spruce on sites infested by Heterobasidion, were investigated on 21 experimental plots in eight 2- to 23-year-old plantations. Heterobasidion root rot became evident about 10 years after planting and the proportion of infected spruces inc...
Article
Full-text available
Genets of Heterobasidion were identified in eight 43- to 56-year-old Norway spruce (Picea abies (L.) Karst.) stands in southern Finland. Four of the stands had been thinned in winter ca. 10years prior to the study, and four had been left unthinned. It was hypothesized that the felling of decayed trees promotes the vegetative spread of the fungus fr...
Article
The occurrence of Heterobasidion annosum in stumps and growing trees was investigated on 15 forest sites in southern Finland where the previous tree stand had been Norway spruce (Picea abies) infected by H. annosum, and the present stand was either Scots pine (Pinus sylvestris), lodgepole pine (Pinus contorta), Siberian larch (Larix siberica), silv...
Article
Spatial distribution of Heterobasidion genets over a period of ca 50 years in two successive generations of Norway spruce (Picea abies) was unravelled. The genets were first identified in 1993 in a naturally regenerated 43-year-old spruce stand that had been thinned the previous winter. Heterobasidion parviporum was found in 17.5% of the old stumps...
Article
Full-text available
The incidence of Heterobasidion root rot in the advance regeneration of Norway spruce (Picea abies (L.) Karst.) was studied in nine stands at four different localities in southern Finland. The mean age of the unthinned advance regeneration on the 17 sample plots ranged from 14 to 44 years. On infested plots, the proportion of Norway spruce infected...
Article
The effects of compensatory fertilization on the infection and growth rate of Heterobasidion annosum were studied in a 40-yr-old, naturally regenerated Scots pine (Pinus sylvestris L.) stand in south-eastern Finland. The treatments were: (1) unfertilized control, (2) a compound fertilizer containing P, K, Ca, Mg, S, Cu, Zn and B, (3) as treatment 2...
Chapter
The effects of nutrient availability on the pest resistance of trees has been studied by surveying damage occurrence and pest populations in fertilised field experiments (population-level studies), and by rearing herbivores and pathogens on fertilised trees or cuttings in the laboratory (individual-level studies). These experiments have clearly sho...
Article
The effects of vitality fertilization on the growth of Heterobasidion annosum in roots of Norway spruce (Picea abies) were studied in a 53-year-old, naturally regenerated spruce stand in southern Finland. The fertilizer treatments were: (1), unfertilized control; (2), a compound fertilizer containing P, K, Ca, Mg, S, Cu, Zn and B; (3), as 2 with ad...
Article
Heterobasidion annosum isolates were collected from spruce, pine and mixed stands growing on forest and former agricultural soils. Intersterility groups of the isolates were identified. Pine was attacked by the P group only and spruce mostly by the S group. Frequency of the P group on spruce was higher on old forest soils and in mixed spruce and pi...
Article
The distribution of different clones (genotypes) ofHeterobasidion annosum was investigated in 34 clear‐cut pure and mixed Norway spruce stands. The proportion of admixed tree species, mostly birch and Scots pine, varied between 0 and 60%. The total area investigated was 35 ha. H. annosum was isolated from 13.1% of the spruces: the S intersterility...

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