Distribution of Viruses Inhabiting Heterobasidion annosum in a Pine-Dominated Forest Plot in Southern Finland

Jurvansuu

Hyder

et al. 2018

J Virol

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The fungal genus 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 (HetPV13-an1) is the main causal agent of severe phenotypic debilitation in the host fungus. Based on RNA sequencing using isogenic virus-infected and cured fungal strains, HetPV13-an1 affected the transcription of 683 genes, of which 60% were downregulated and 40% upregulated. Alterations observed in carbohydrate and amino acid metabolism suggest that the virus causes a state of starvation, which is compensated for by alternative synthesis routes. We used dual cultures to transmit HetPV13-an1 into new strains of and The three strains of that acquired the virus showed noticeable growth reduction on rich culturing medium, while only two of six isolates tested showed significant debilitation. Based on reverse transcription-quantitative PCR (RT-qPCR) analysis, the response toward HetPV13-an1 infection was somewhat different in and We assessed the effects of HetPV13-an1 on the wood colonization efficacy of in a field experiment where 46 Norway spruce trees were inoculated with isogenic strains with or without the virus. The virus-infected strain showed considerably less growth within living trees than the isolate without HetPV13-an1, indicating that the virus also causes growth debilitation in natural substrates. A biocontrol method restricting the spread of species would be highly beneficial to forestry, as these fungi are difficult to eradicate from diseased forest stands and cause approximate annual losses of €800 million in Europe. We used virus curing and reintroduction experiments and RNA sequencing to show that the alphapartitivirus HetPV13-an1 affects many basic cellular functions of the white rot wood decay fungus, which results in aberrant hyphal morphology and a low growth rate. Dual fungal cultures were used to introduce HetPV13-an1 into a new host species, , and field experiments confirmed the capability of the virus to reduce the growth of in living spruce wood. Taken together, our results suggest that HetPV13-an1 shows potential for the development of a future biocontrol agent against fungi.

Section: Discussionmentioning

confidence: 98%

Heterobasidion Partitivirus 13 Mediates Severe Growth Debilitation and Major Alterations in the Gene Expression of a Fungal Forest Pathogen

Jurvansuu

Hyder

et al. 2018

J Virol

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“…It is not known how often highly similar viruses' effects on their hosts differ. In this respect it is, however, interesting that the phenotypic effects of HetPV13-an2 ( H. annosum S45-8) with 97% nt RdRp/CP similarity to HetPV13-an1 (Kashif et al, 2015; Hyder et al, 2018) did not show similar negative effects on its native host.…”

Section: Discussionmentioning

confidence: 99%

“…Multiple virus infections are common among Heterobasidion strains (Vainio et al, 2012, 2013, 2015a,b; Kashif et al, 2015; Hyder et al, 2018) as well as other fungi such as Gremmeniella abietina (Tuomivirta and Hantula, 2005; Botella et al, 2013), Rhizoctonia solani (Lakshman et al, 1998), Helminthosporium victoriae (Ghabrial et al, 2013), Cryphonectria parasitica (Peever et al, 1997), and Sclerotinia sclerotiorum (Marzano et al, 2015). The interactions between co-infecting viruses and their hosts may have a major effect on the ecology of both fungi and their viruses.…”

Section: Introductionmentioning

confidence: 99%

Alphapartitiviruses of Heterobasidion Wood Decay Fungi Affect Each Other's Transmission and Host Growth

Kashif

Jurvansuu

Front. Cell. Infect. Microbiol.

et al. 2019

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Heterobasidion spp. root rot fungi are highly destructive forest pathogens of the northern boreal forests, and are known to host a diverse community of partitiviruses. The transmission of these mycoviruses occurs horizontally among host strains via mycelial anastomoses. We revealed using dual cultures that virus transmission rates are affected by pre-existing virus infections among two strains of H. annosum . The transmission efficacy of mycovirus HetPV15-pa1 to a pre-infected host was elevated from zero to 50% by the presence of HetPV13-an1, and a double infection of these viruses in the donor resulted in an overall transmission rate of 90% to a partitivirus-free recipient. On contrary, pre-existing virus infections of two closely related strains of HetPV11 hindered each other's transmission, but had unexpectedly dissimilar effects on the transmission of more distantly related viruses. The co-infection of HetPV13-an1 and HetPV15-pa1 significantly reduced host growth, whereas double infections including HetPV11 strains had variable effects. Moreover, the results showed that RdRp transcripts are generally more abundant than capsid protein (CP) transcripts and the four different virus strains express unique transcripts ratios of RdRp and CP. Taken together, the results show that the interplay between co-infecting viruses and their host is extremely complex and highly unpredictable.

“…Moreover, the rate of the fungal spread could slow down due to reduced vitality of the Heterobasidion mycelium, for example, due to aging [8] and/or virus infections [35][36][37]. As shown in an earlier study carried out on the same experimental site [19], 29% of the Heterobasidion genets and 22% of the isolates identified in the previous tree generation were infected by dsRNA viruses of the family Partitiviridae, which is a considerably higher prevalence of these viruses than is typically observed among isolates of Heterobasidion spp. in culture collections [38] but resembles our findings in H. parviporum genets at a spruce-dominated forest site heavily infested by the pathogen [39].…”

Section: Incidence Of Heterobasidion Root Rot In the Previous Scots Pine Rotationmentioning

confidence: 92%

“…Pine trees with thin or chlorotic crowns, reduced height growth, or distress cones were classified as infected by H. annosum s.s. In total, nine separated disease centers with one to nine mature trees in poor condition were found [19]. All dead and infected trees, as well as one or two of the nearest healthy-looking mature trees, were marked with a label below the stump height.…”

Section: Monitoring Heterobasidion Root Rot In the Previous Tree Generationmentioning

confidence: 99%

High Seedling Mortality of Scots Pine Caused by Heterobasidion annosum s.s.

Piri

Nuorteva

et al. 2021

Forests

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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-cutting area (c. 1.2 ha in size) after a pine generation that showed slight external symptoms of Heterobasidion root rot. The first dead seedlings were found five years after planting and during a nine-year monitoring period; nearly 600 seedlings were killed by H. annosum s.s. in 48 individual disease centers. Based on pairing tests of 482 isolates, 117 different H. annosum s.s. genotypes were identified. On average, 2.9 genotypes occurred in a single disease center. The extensive secondary spread of genotypes within root systems (up to 48 pine seedlings infected by the same genotype) resulted in annually expanding disease centers. In addition, more than half of the seedlings killed by H. annosum s.s. produced perennial fruiting bodies thus providing air-borne inoculum. The risk of spore infection should be taken into account in any type of cutting operation in young pine stands. Moreover, new control measures directed towards the secondary spread of H. annosum s.s. in pine regeneration are urgently needed in order to maintain the productivity of the pine forest on infested sites.