Publikasjoner
NIBIOs ansatte publiserer flere hundre vitenskapelige artikler og forskningsrapporter hvert år. Her finner du referanser og lenker til publikasjoner og andre forsknings- og formidlingsaktiviteter. Samlingen oppdateres løpende med både nytt og historisk materiale. For mer informasjon om NIBIOs publikasjoner, besøk NIBIOs bibliotek.
2018
Sammendrag
Bark beetles and their symbiotic bluestain fungi kill more trees than all other natural factors and cause great economic losses in Norway spruce and other conifers. The tree's natural defenses are the most important factor maintaining bark beetle-fungus complexes at low, endemic levels. Spraying Norway spruce trees with the plant hormone methyl jasmonate (MeJA) primes tree defenses without eliciting notable induced defenses, but enables the trees to respond much more quickly and strongly when challenged by bark beetles or fungi several weeks after treatment. This phenomenon, known as defense priming, is a form of acquired resistance that enables cost-effective and vigorous defense responses. In field experiments with 50-year-old clonal spruce trees terpene concentrations in the bark increased 60-fold within 24 h after mechanical wounding of MeJA primed trees, compared with a 13-fold increase in unprimed control trees. We also observed altered transcriptional patterns in primed trees using Illumina deep transcriptome sequencing. When wounded, primed trees launched vigorous induced defenses with significant differential regulation of gene transcripts, such as those involved in phenylpropanoid synthesis leading to lignification. Resistance-like genes, such as the NB-LRR coding genes, are also more rapidly induced in primed than in unprimed trees. Transcriptome results from primed but unwounded trees indicate an alteration in the state of the chromatin, resembling changes associated with the activity of the epigenetic machinery creating long-lasting epigenetic marks. We do not know yet how long the primed state is activated in Norway spruce, but our data so far indicate that it may last for at least 3 years.
Forfattere
Pieternella C. Luttikhuizen Freek H. M. van den Heuvel Celine Rebours Harry J. Witte Judith D. L. van Bleijswijk Klaas TimmermansSammendrag
Kelp aquaculture is globally developing steadily as human food source, along with other applications. One of the newer crop species is Saccharina latissima, a northern hemisphere kelp inhabiting temperate to arctic rocky shores. To protect and docu-ment its natural genetic variation at the onset of this novel aquaculture, as well as increase knowledge on its taxonomy and phylogeography, we collected new geneticdata, both nuclear and mitochondrial, and combined it with previous knowledge to estimate genetic connectivity and infer colonization history. Isolation-with- migration coalescent analyses demonstrate that gene flow among the sampled locations is vir -tually nonexistent. An updated scenario for the origin and colonization history of S. latissima is developed as follows: We propose that the species (or species complex) originated in the northwest Pacific, crossed to the northeast Pacific in the Miocene, and then crossed the Bering Strait after its opening ~5.5 Ma into the Arctic and northeast Atlantic. It subsequently crossed the Atlantic from east to west. During the Pleistocene, it was compressed in the south with evidence for northern refugia in Europe. Postglacial recolonization led to secondary contact in the Canadian Arctic. Saccharina cichorioides is shown to probably belong to the S. latissima species com -plex and to derive from ancestral populations in the Asian North Pacific. Our novel approach of comparing inferred gene flow based on coalescent analysis versus Wright’s island model suggests that equilibrium levels of differentiation have not yet been reached in Europe and, hence, that genetic differentiation is expected to in -crease further if populations are left undisturbed.
Forfattere
Victor Phani Vishal S. Somvanshi Rohit N. Shukla Keith Davies Uma RaoSammendrag
Background: Southern root-knot nematode Meloidogyne incognita (Kofoid and White, 1919), Chitwood, 1949 is a key pest of agricultural crops. Pasteuria penetrans is a hyperparasitic bacterium capable of suppressing the nematode reproduction, and represents a typical coevolved pathogen-hyperparasite system. Attachment of Pasteuria endospores to the cuticle of second-stage nematode juveniles is the first and pivotal step in the bacterial infection. RNA-Seq was used to understand the early transcriptional response of the root-knot nematode at 8 h post Pasteuria endospore attachment. Results: A total of 52,485 transcripts were assembled from the high quality (HQ) reads, out of which 582 transcripts were found differentially expressed in the Pasteuria endospore encumbered J2 s, of which 229 were up-regulated and 353 were down-regulated. Pasteuria infection caused a suppression of the protein synthesis machinery of the nematode. Several of the differentially expressed transcripts were putatively involved in nematode innate immunity, signaling, stress responses, endospore attachment process and post-attachment behavioral modification of the juveniles. The expression profiles of fifteen selected transcripts were validated to be true by the qRT PCR. RNAi based silencing of transcripts coding for fructose bisphosphate aldolase and glucosyl transferase caused a reduction in endospore attachment as compared to the controls, whereas, silencing of aspartic protease and ubiquitin coding transcripts resulted in higher incidence of endospore attachment on the nematode cuticle. Conclusions: Here we provide evidence of an early transcriptional response by the nematode upon infection by Pasteuria prior to root invasion. We found that adhesion of Pasteuria endospores to the cuticle induced a downregulated protein response in the nematode. In addition, we show that fructose bisphosphate aldolase, glucosyl transferase, aspartic protease and ubiquitin coding transcripts are involved in modulating the endospore attachment on the nematode cuticle. Our results add new and significant information to the existing knowledge on early molecular interaction between M. incognita and P. penetrans.
Forfattere
Leonardo Ciaccheri Lorenza Tuccio Andrea A. Mencaglia Anna G. Mignani Ewelina Hallmann Kalina Sikorska-Zimny Stanislaw Kaniszewski Michel Verheul Giovanni AgatiSammendrag
Non-destructive tools for evaluating the lycopene content in tomatoes are of great interest to the entire fruit chain because of an increasing demand for beneficial health products. With the aim of developing compact low-cost reflectance sensors for lycopene determination, we compared Partial Least Squares (PLS) prediction models by using either directional or total reflectance in the 500–750 nm range. Directional reflectance at 45° with respect to the LED lighting direction was acquired by means of a compact spectrometer sensor. Total reflectance was acquired through a 50-mm integrating sphere connected to a spectrometer. The analysis was conducted on two hydroponic greenhouse cultivated red tomato varieties, namely the large round ‘Dometica’ (average diameter: 57 mm) and the small cherry ‘Juanita’ (average diameter: 26 mm). For both varieties, the spectral variance of directional reflectance was well correlated to that of total reflectance. The performances of the PLS prediction models were also similar, with R2 of cross-validation between 0.73 and 0.81. The prediction error, relative to the mean lycopene content of full ripe tomatoes, was similar: i.e. around 16–17% for both varieties and sensors. Our results showed that directional reflectance measured by means of portable, low-cost and compact LED-based sensors can be used with an adequate precision for the non-destructive assessment of lycopene in tomatoes.
Forfattere
Shinsaku Sasai Keisuke Tamura Motoaki Tojo Maria-Luz Herrero Tamotsu Hoshino Satoshi T. Ohki Tomofumi MochizukiSammendrag
We investigated virus infection in the oomycete Pythium polare from the Arctic. From 39 isolates investigated, 14 contained virus-like double-stranded RNA (dsRNA). Next generation sequencing revealed that the P. polare isolate OPU1176 contained three different virus-like sequences. We determined the full-length genome sequence of one of them. The 5397 nt-length genome had two overlapped open reading frames (ORFs) consistent with a toti and toti-like viruses, that we named Pythium polare RNA virus 1 (PpRV1). The ORF2 encoded an RNAdependent RNA polymerase (RdRp). The shifty heptamer motif and RNA pseudoknot were predicted near the stop codon of ORF1, implying that the RdRp could be translated as a fusion protein with the ORF1 protein. Phylogenetic analysis with deduced RdRp amino acid sequences indicated that oomycete virus PpRV1 was closely related to the unclassified arthropod toti-like viruses. The comparison of PpRV1-free and -infected lines suggested that PpRV1 infected in a symptomless manner.
Forfattere
Johannes Deelstra Sekhar Udaya Nagothu Krishna R. Kakumanu Yella R. Kaluvai Surresh R. KallamSammendrag
Saving water in irrigated agriculture is a high priority in areas with scarce water resources and impacted by climate change. This paper presents results of measurements on water Productivity (WP) under alternative rice growing practices such as alternating wetting and drying,direct seeded rice, modified systems of rice intensification and conventional paddy rice (NI)in two selected districts (Guntur in Andhra Pradesh and Nalgonda in Telangana, India). Under alternative practices, the yields varied from 5.72 to 6.11 t/ha compared with 4.71 t/ha under paddy rice. The average water application varied from 991 to 1494 mm under alternative practices while average application in conventional paddy rice was 2242 mm. Higher yield and lower water application led to an increase in WP varying from 0.45 to 0.59 kg/m3 under alternative practices compared with 0.22 kg/m3 under conventional paddy rice. The measurements showed that less water can be used to produce more crop under alternative rice growing practices. The results are important for water-scarce areas, providing useful information to policy makers, farmers, agricultural departments and water management boards in devising future climate-smart adaptation and mitigation strategies.
Forfattere
Tao Zhao Dineshkumar Kandasamy Paal Krokene Jingyuan Chen Jonathan Gershenzon Almuth HammerbacherSammendrag
The bark beetle Ips typographus carries numerous fungi that could be assisting the beetle in colonizing live Norway spruce (Picea abies) trees. Phenolic defenses in spruce phloem are degraded by the beetle's major tree-killing fungus Endoconidiophora polonica, but it is unknown if other beetle associates can also catabolize these compounds. We compared the ability of five fungi commonly associated with I. typographus to degrade phenolic compounds in Norway spruce phloem. Grosmannia penicillata and Grosmannia europhioides were able to degrade stilbenes and flavonoids faster than E. polonica and grow on minimal growth medium with spruce bark constituents as the only nutrients. Furthermore, beetles avoided medium amended with phenolics but marginally preferred medium colonized by fungi. Taken together our results show that different bark beetle-associated fungi have complementary roles in degrading host metabolites and thus might improve this insect's persistence in well defended host tissues.
Forfattere
Shota Masumoto Motoaki Tojo Satoshi Imura Maria-Luz Herrero Masaki UchidaSammendrag
The parasitic fungus Rhytisma polare is a common parasite on leaves of the polar willow (Salix polaris) in the high-Arctic polar semi-desert of Spitsbergen, Norway. Because Rhytisma spp. generally requires saturation with free water to develop ascospores, it is unclear how R. polare has ecologically adapted to the Arctic desert, where such water is very limited. In this study, the response of R. polare to diferent water conditions on Spitsbergen was investigated during the summer months of June–August in 2012. Field and laboratory experiments demonstrated that free water availability from rainfall or snowmelt is essential to facilitate ascostromal maturation and ascospore dispersal in R. polare. The feld experiments also revealed that the dispersal of ascospores produced on fallen leaves did not extend beyond a few meters. These results suggest that the free water requirement combined with the short spore-dispersal distance constrains the local occurrence of R. polare in the Arctic desert to locations where free water from rainfall and snowmelt is present.
Forfattere
Andre Acksel Luise Giani Carolin Stasch Peter Kühn Sebastian Eiter Kerstin Potthoff Tom Regier Peter LeinweberSammendrag
Some previous studies showed that the formation of several deep dark humus-rich topsoils in Northern Europe was strongly influenced by the application of different organic materials by anthropogenic activities in former times. Such topsoils classified as plaggic Anthrosols also occurred in the Jæren region in SW Norway. However, source material and formation time of these Plaggic Anthrosols have not yet been clarified. Close to this region we found further humus-rich topsoils in the Karmøy municipality (2 sites at main island of Karmøy and 1 site at Feøy). These soils show a thick humus-rich topsoil up to 30 cm, and their formation cannot only be explained by natural conditions. We analyzed the molecular signature of the soil organic matter (SOM) by benzene polycarboxylic acids (BPCA), non-targeted bulk SOM mass spectrometry, δ34S and 14C AMS dating in order to determine source materials and the age of the SOM. The black carbon (BC) contents of the plaggic soils in Jæren (mean 3.4 g kg−1) deliver clear evidence for inputs of combustion residues from ancient fire management and/or from settlements. The C-XANES and Py-FIMS-spectra reveal relative enrichments of aromatic C and heterocyclic N compounds in the plaggic soils corresponding to the BC contents. In contrast, the humus-rich topsoils in Karmøy seem to be unaffected by fire management due to the low BC contents (mean 0.6 g kg−1) and the relative low portions of aromatic C and heterocyclic N compounds from C-XANES and Py-FIMS. The δ34S isotope signature of the SOM ranged from 10.6 to 15.2‰ in the soils at the islands and 10.0 to 13.5‰ in Jæren, corresponding to the Anthrosols in the Baltic Sea region (Median: δ34S = 11.5‰) and suggest an input of marine biomass (δ34S of seaweed = 20‰). The AMS 14C dating and complementary archaeological literature implied that the soils in Jæren and Karmøy have been formed between the Roman Iron Age (500 BC to AD 500) and the Viking Age (AD 800 to AD 1,000). Our results provide strong evidence for an anthropo-pedogenesis of the humus-rich topsoils in Karmøy and indicate parallels to the plaggic soils in Jæren as well as to Anthrosols in the Baltic Sea region. Therefore, we propose to classify the humus-rich topsoils in Karmøy as Anthrosols.
Forfattere
Marie-Laure Desprez-Loustau Marie Massot Maude Toïgo Tania Fort Ayse Gülden Aday Kaya Johanna Boberg Uwe Braun Xavier Capdevielle Thomas Cech Anne Chandelier Petya Christova Tamara Corcobado Tugba Dogmus Cyril Dutech Olivier Fabreguettes Julie Faivre d'Arcier Andrin Gross Marilia Horta Jung Eugenia Iturritxa Thomas Jung Corina Junker Levente Kiss Kaloyan Kostov Asko Lehtijarvi Aneta Lyubenova Benoit Marçais Jonas Oliva Funda Oskay Martin Pastirčák Katarína Pastircakova Dominique Piou Gilles Saint-Jean Arnaud Sallafranque Slavtcho Slavov Jan Stenlid Venche Talgø Susumu Takamatsu Ayco JM. TackSammendrag
The spatial distribution and niche differentiation of three closely related species (Erysiphe alphitoides, Erysiphe quercicola and Erysiphe hypophylla) causing oak powdery mildew was studied at scales ranging from the European continent, where they are invasive, to a single leaf. While E. alphitoides was dominant at all scales, E. quercicola and E. hypophylla had restricted geographic, stand and leaf distributions. The large-scale distributions were likely explained by climatic factors and species environmental tolerances, with E. quercicola being more frequent in warmer climates and E. hypophylla in colder climates. The extensive sampling and molecular analyses revealed the cryptic invasion of E. quercicola in nine countries from which it had not previously been recorded. The presence of the three species was also strongly affected by host factors, such as oak species and developmental stage. Segregation patterns between Erysiphe species were observed at the leaf scale, between and within leaf surfaces, suggesting competitive effects.