Genetic control of susceptibility to fungal symbionts of juvenile Norway spruce (Picea abies (L.) H. Karsten) in relation to long-term growth performance

This study was carried out in order to reveal the degree to which host-tree factors influence the interaction between Norway spruce (Picea abies (L.) Karst.) and the endophytic (EN) and ectomycorrhizal fungi (EMF) found in their needles and roots, respectively. We also explored how susceptibility to fungal infection and the composition and functionality of associated fungal communities relates to seedling growth performance. In multiple glasshouse experiments, we challenged Norway spruce seedlings and clonal cuttings with pure culture and natural EMF inoculum. Clonal cuttings from healthy spruce were used to assess the heritability of EMF communities and needle endophytes. The relationship between the susceptibility to fungal infection and EMF community function with host-tree performance was studied using seedlings originating from families known to have different growth rates at later life stages. We also examined resource allocation and root architecture of the fast- and slow-growing Norway spruce seedlings. Hypotheses derived prior to and during this work were tested with molecular tools and appropriate statistical techniques. Host genotype partly controlled the colonization of EMF and EN species but future growth performance was not associated with susceptibility. Norway spruce seedlings originating from differently growing seed orchards were colonized similarly by EMF, and did not show any consistent bias in terms of infection rate or the function of single ectomycorrhizas. However, the short root architecture was found to be moderately heritable and varied consistently between the fast- and slow-growing origins. We observed seedlings of fast-growing origins to have sparse and widespread rootlets that enable a greater allocation of below-ground biomass and higher exoenzyme capacity compared to slow-growing seedlings. Norway spruce does not show a strong genetic signal for within-population selection towards its mutualistic fungi at the species level. Formation of the associated EMF community may be an effect rather than cause of seedling physiological state. The superior growth of fast-growing genotypes seems to be a consequence of resource allocation and optimal root structuring in the juvenile stage rather than the extent of colonization by fungal mutualists. We accept that root physiological factors may subsequently lead to a higher capacity for symbiotic interactions in heterogeneous forest soil and a higher diversity and functionality of associated EMF. An adequate and versatile means of nutrient acquisition is an important factor enabling fast growth, but might also provide the basis for positive feedback via enhanced relationships with mutualistic fungi.Työssä tutkittiin metsäkuusen (Picea abies (L.) Karst.) perimän vaikutusta taimivaiheen neulas- ja juurisieniyhteisöjen rakenteeseen, ja näiden sieniyhteisöjen yhteyttä isäntäpuun kasvuun, resurssien kohdentamiseen sekä juuriston rakenteeseen. Kuusen siementaimia ja klonaalisia pistokkaita altistettiin symbionttisille pintasienijuurisienille ja taudinaiheuttajasienille kasvihuonekokeissa, ja altistuksia seuranneita vuorovaikutuksia tutkittiin molekyylibiologisten ja tilastollisten menetelmien avulla. Klonaalisten pistokastaimien avulla tutkittiin kuusentaimien neulasendofyyttien ja pintasienijuurisienten yhteisörakenteen periytyvyyttä. Infektioalttiuden ja pintasienijuurten toiminnan yhteyttä kasvuun tutkittiin puolestaan eri alkuperää olevilla kuusen siementaimilla, jotka poikkesivat toisistaan myöhemmän kasvuvaiheen ilmiasultaan. Isäntäpuu sääteli osittain neulasendofyyttien ja pintasienijuurisienten kolonisaatiota mutta ei suoraan sienten lajimäärää tai infektioalttiutta. Myöhemmässä kasvuvaiheessa nopeasti ja hitaasti kasvavien kuusentaimien pintasienijuurisienten yhteisörakenteet olivat hyvin samanlaiset, eikä infektioherkkyydessä tai pintasienijuurten toiminnassa ollut eroja näiden taimiryhmien välillä. Suurimmat erot nopea- ja hidaskasvuisten kuusialkuperien siementaimien välillä ilmenivät juurten haarautumisessa ja resurssien kohdentamisessa. Hitaasti kasvavista alkuperistä peräisin olevat siementaimet kasvattivat tiheät juuristot, joissa oli paljon juurenkärkiä. Nopeakasvuisten alkuperien taimet kohdensivat enemmän resursseja maanalaiseen kasvuun, ja niiden juuret levittäytyivät hidaskasvuisia taimia laajemmalle, ja juuristotasolla niillä oli myös enemmän ravinteidenottopotentiaalia kuin hitaasti kasvavien alkuperien taimilla. Kuusi on elänyt miljoonia vuosia tiiviisti rinnakkain symbionttisten sientensä kanssa, ja tutkimustulostemme perusteella näyttää siltä, ettei kuusella esiinny voimakasta populaation sisäistä geneettistä valintaa sieniyhteisöjen lajeja kohtaan. Kuusen sieniyhteisöt eivät suoraan näytä säätelevän taimivaiheen elinvoimaisuutta, vaan ne saattavat pikemminkin heijastella isännän fysiologista tilaa. Hyvän kasvun salaisuus saattaa piillä resurssien kohdentamisessa oikeassa suhteessa maan alle erityisesti taimivaiheen aikana. Pitkällä aikavälillä riittävät juuriresurssit mahdollistavat kuuselle monipuolisen pintasienijuurisieniyhteisön kehityksen, joka puolestaan takaa monipuolisen toiminnan kautta riittävän veden ja ravinteiden saannin karussa metsämaassa. Hyvä ravinnetila voi edelleen johtaa kerääntyvän hyvän kierteeseen, joka voi olla yksi syy kuusen kasvueroihin

Boreal soil microbial diversity and seed onion mycorrhizal colonization is unaffected by preceding one season crop cultivation

Arbuscular mycorrhizal fungi (AMF) enhance plant phosphorus uptake, increase soil water holding abilities, reduce soil erosion and can protect their hosts from soil-borne pathogens. Hence, AMF play an important part in improving sustainable agricultural practices, and information about the effects of different preceding crop species on the following crop's AMF well-being is crucial for designing crop rotations. We studied onion root and soil microbial diversity and onion root AMF colonization rates after being preceded by three AMF hosting and one non-hosting green manure crop species in a boreal climate organic field. One-season cultivation of different preceding green manure crops did not have a strong effect on AMF colonization or microbial diversity in onion roots nor in the surrounding soil. Onions had high AMF colonization and microbial diversity after all four preceding crops. The overall fungal and bacterial populations of the soil reacted more strongly to seasonal variations than preceding crops. The study suggests that one season is a too short time to influence the AMF community in boreal climate organic fields with conventional tillage. Thus, non-host preceding crops can also be used in rotations, especially together with AMF host crops.Peer reviewe

Fast and reliable method to estimate global DNA methylation in plants and fungi with high-pressure liquid chromatography (HPLC)-ultraviolet detection and even more sensitive one with HPLC-mass spectrometry

Abstract: DNA (Deoxyribonucleic acid) methylation is one of the epigenetic modifications of DNA, acting as a bridge between genotype and phenotype. Thus, disruption of DNA methylation pattern has tremendous consequences for organism development. Current methods to determine DNA methylation suffer from methodological drawbacks like high requirement of DNA and poor reproducibility of chromatograms. Here we provide a fast and reliable method using high-pressure liquid chromatography (HPLC)-ultraviolet (UV) detector and even more sensitive one with HPLC- mass spectrometry (MS) and we test this method with various plant and fungal DNA isolates. We optimized the preparation of the DNA degradation step to decrease background noise, we improved separation conditions to provide reliable and reproducible chromatograms and conditions to measure nucleotides in HPLC-MS. We showed that global DNA methylation level can be accurately and reproducibly measured with as little as 0.2 µM for HPLC-UV and 0.02 µM for HPLC-MS of methylated cytosine

Early root growth and architecture of fast- and slow-growing Norway spruce (Picea abies) families differ-potential for functional adaptation

The relationship between the growth rate of aboveground parts of trees and fine root development is largely unknown. We investigated the early root development of fast-and slow-growing Norway spruce (Picea abies (L.) H. Karst.) families at a developmental stage when the difference in size is not yet observed. Seedling root architecture data, describing root branching, were collected with the WinRHIZO (TM) image analysis system, and mixed models were used to determine possible differences between the two growth phenotypes. A new approach was used to investigate the spatial extent of root properties along the whole sample root from the base of 1-year-old seedlings to the most distal part of a root. The root architecture of seedlings representing fastgrowing phenotypes showed similar to 30% higher numbers of root branches and tips, which resulted in larger root extensions and potentially a better ability to acquire nutrients. Seedlings of fast-growing phenotypes oriented and allocated root tips and bio-mass further away from the base of the seedling than those growing slowly, a possible advantage in nutrient-limited and heterogeneous boreal forest soils. We conclude that a higher long-term growth rate of the aboveground parts in Norway spruce may relate to greater allocation of resources to explorative roots that confers a competitive edge during early growth phases in forest ecosystems.Peer reviewe

Jättiputket

Jättiputket valtaavat kasvutilaa muilta lajeilta, yksipuolistavat maisemaa ja ovat vaarallisia ihmisen terveydelle

Pheromone-based monitoring of invasive alien insects along the border of Finland and Russia – methods and unintentionally caught species

Global trade provides pathways for the spread of invasive species. To tackle the threat, many countries have designated surveys that are typically conducted at the probable ports of entry. For Finland, the most north-eastern region of the European Union (EU), such site is the border with Russia and the imports of coniferous roundwood and wood chips. In this paper, we describe the monitoring systems based on pheromone-trapping for three EU-wide quarantine pests: Dendrolimus sibiricus, Polygraphus proximus and Bursaphelenchus xylophilus. We also list the non-target species caught in an exploratory survey using pheromone traps. During the three years of survey, no quarantine pests were detected, but 30 other species of insects were caught. Therefore, the monitoring – despite not detecting the target pests – provided information about the abundance of other species. As insect diversity reflects the status of the surrounding environment, the value of such data should be increased via co-operation among research institutes

Defoliation of Tilia cordata trees associated with Apiognomonia errabunda infection in Finland

We investigated the causative agent of a disease outbreak affecting small-leaved limes (Tilia cordata Mill.) and resulting in darkening of the leaf petioles and excessive defoliation during summer 2016 in southern Finland. The fungal species composition of the symptomatic petioles was examined by culture isolation and molecular identification using ITS rDNA sequences, which revealed the most prevalent fungal species present in the petioles as Apiognomonia errabunda (Roberge) Hhn. Based on reviewing curated herbarium specimens deposited at the Universities of Helsinki and Turku, A. errabunda is native and widely distributed in small-leaved limes in Finland, and occasionally infects also other broadleaved trees, including Quercus robur L. and ornamental species of Tilia L. and Fagus L. The ITS sequence analysis conducted during this study revealed minor within-species polymorphisms similar to those observed earlier in the Central European and Russian populations of A. errabunda, and reports the first nucleotide sequences of this species from the Nordic countries.Peer reviewe

Long-term impacts of organic and conventional farming on the soil microbiome in boreal arable soil

Long-term effects of organic and conventional farming systems in parallel on the microbiota of boreal arable soil from forage and cereal crop fields were investigated. Microbial activity was measured as basal respiration and microbial biomass C and N were determined by fumigation extraction. Microbial abundance was determined by gene copy numbers from bacterial and archaeal specific 16S rRNA genes and the fungal ITS2 region with quantitative PCR. Microbial community composition for soil bacteria and fungi, including arbuscular mycorrhiza, were conducted by amplicon sequencing with richness assessed from OTU reads. We detected changes in both bacterial and fungal community composition between the farming systems. Microbial activity and biomass C and N were higher in the organic system for cereal crop rotation compared to the respective conventional system. In the autumn, organic systems had higher microbial richness. As fungi were more abundant in the autumn, they may be responsible for both higher microbial activity and C sequestration in their biomass after harvesting, especially in the organic system for cereal crop rotation. Also, crop type and cow manure explained changes in fungal community composition. The typical bacterial community of the organic system for cereal crop rotation included many soil and plant health promoting bacterial groups. Fungi benefiting from organic farming practices, other than manure, may include endophytic taxa with a variety of functions as well as pathogenic and mycotoxin producing species. Overall, the results suggest that farming practices typical of organic farming, such as use of green manure and continuous plant cover have induced changes in the soil microbiome

Impacts of coniferous bark-derived organic soil amendments on microbial communities in arable soil – a microcosm study

A decline in the carbon content of agricultural soils has been reported globally. Amendments of forest industry side-streams might counteract this. We tested the effects of industrial conifer bark and its cascade process materials on the soil microbiome under barley (Hordeum vulgare L.) in clay and silt soil microcosms for 10 months, simulating the seasonal temperature changes of the boreal region. Microbial gene copy numbers were higher in clay soils than in silt. All amendments except unextracted bark increased bacterial gene copies in both soils. In turn, all other amendments, but not unextracted bark from an anaerobic digestion process, increased fungal gene copy numbers in silt soil. In clay soil, fungal increase occurred only with unextracted bark and hot water extracted bark. Soil, amendment type and simulated season affected both the bacterial and fungal community composition. Amendments increased bacteria originating from the anaerobic digestion process, as well as dinitrogen fixers and decomposers of plant cells. In turn, unextracted and hot water extracted bark determined the fungal community composition in silt. As fungal abundance increase and community diversification are related to soil carbon acquisition, bark-based amendments to soils can thus contribute to sustainable agriculture