Publications
NIBIOs employees contribute to several hundred scientific articles and research reports every year. You can browse or search in our collection which contains references and links to these publications as well as other research and dissemination activities. The collection is continously updated with new and historical material.
2023
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Abstract
Phytophthora cactorum has two distinct pathotypes that cause crown rot and leather rot in strawberry (Fragaria × ananassa). Strains of the crown rot pathotype can infect both the rhizome (crown) and fruit tissues, while strains of the leather rot pathotype can only infect the fruits of strawberry. The genome of a highly virulent crown rot strain, a low virulent crown rot strain, and three leather rot strains were sequenced using PacBio high fidelity (HiFi) long read sequencing. The reads were de novo assembled to 66.4–67.6 megabases genomes in 178–204 contigs, with N50 values ranging from 892 to 1,036 kilobases. The total number of predicted complete genes in the five P. cactorum genomes ranged from 17,286 to 17,398. Orthology analysis identified a core secretome of 8,238 genes. Comparative genomic analysis revealed differences in the composition of potential virulence effectors, such as putative RxLR and Crinklers, between the crown rot and the leather rot pathotypes. Insertions, deletions, and amino acid substitutions were detected in genes encoding putative elicitors such as beta elicitin and cellulose-binding domain proteins from the leather rot strains compared to the highly virulent crown rot strain, suggesting a potential mechanism for the crown rot strain to escape host recognition during compatible interaction with strawberry. The results presented here highlight several effectors that may facilitate the tissue-specific colonization of P. cactorum in strawberry.
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2022
Authors
Ari Hietala Ahto Agan Nina Elisabeth Nagy Isabella Børja Volkmar Timmermann Rein Drenkhan Halvor SolheimAbstract
The populations of European ash and its harmless fungal associate Hymenoscyphus albidus are in decline owing to ash dieback caused by the invasive Hymenoscyphus fraxineus, a fungus that in its native range in Asia is a harmless leaf endophyte of local ash species. To clarify the behavior of H. albidus and its spatial and temporal niche overlap with the invasive relative, we used light microscopy, fungal species-specific qPCR assays, and PacBio long-read amplicon sequencing of the ITS1-5.8S-ITS2 region to examine fungal growth and species composition in attached leaves of European ash. The plant material was collected from a healthy stand in central Norway, where ash saplings in late autumn showed leaflet vein necrosis like that commonly related to H. fraxineus. For reference, leaflet samples were analyzed from stands with epidemic level of ash dieback in southeastern Norway and Estonia. While H. albidus was predominant in the necrotic veins in the healthy stand, H. fraxineus was predominant in the diseased stands. Otherwise, endophytes with pathogenic potential in the genera Venturia (anamorph Fusicladium), Mycosphaerella (anamorph Ramularia), and Phoma, and basidiomycetous yeasts formed the core leaflet mycobiome both in the healthy and diseased stands. In necrotic leaf areas with high levels of either H. albidus or H. fraxineus DNA, one common feature was the high colonization of sclerenchyma and phloem, a region from which the ascomata of both species arise. Our data suggest that H. albidus can induce necrosis in ash leaves, but that owing to low infection pressure, this first takes place in tissues weakened by autumn senescence, 1–2 months later in the season than what is characteristic of H. fraxineus at an epidemic phase of ash dieback. The most striking difference between these fungi would appear to be the high fecundity of H. fraxineus. The adaptation to a host that is phylogenetically closely related to European ash, a tree species with high occurrence frequency in Europe, and the presence of environmental conditions favorable to H. fraxineus life cycle completion in most years may enable the build-up of high infection pressure and challenge of leaf defense prior to autumn senescence.
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Authors
Heidi Udnes Aamot Hesam Mousavi Jafar Razzaghian Guro Brodal Michael Sulyok Rudolf Krska Simon G. Edwards Ingerd Skow HofgaardAbstract
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Authors
Heidi Udnes Aamot Simeon Rossmann Erik Lysøe Guro Brodal Birgitte Henriksen Ruth Dill-Macky Carl Gunnar Fossdal Ingerd Skow HofgaardAbstract
We used metabarcoding of ITS 1 and 2 to compare the mycobiome of Norwegian spring wheat seed lots of two commonly grown spring wheat varieties (Mirakel and Zebra) harvested in 2016 and 2017. The seed lots varied in germination and were grouped according to high and low germination (≥90% and <90% germinated seeds, respectively) determined by the ISTA germination method. In addition, the percentage of each seed lot infested by the most important wheat pathogens (Microdochium spp., Fusarium spp., and Parastagonospora nodorum) was determined using a plate-out test on PDA, and species-specific qPCR was used to quantify the amount of DNA of F. avenaceum, F. culmorum, F. graminearum, F. poae, M. majus, M. nivale, and P. nodorum. Our study indicated that the presence of Microdochium was most associated with poor germination (which is as expected), while P. nodorum; although present at relatively high levels, apparently had limited impact on germination. Among the species quantified by qPCR, M. majus was the most abundant, F. avenaceum was detected at low levels, whereas the other fusaria were barely detected. Metabarcoding data indicated a negative association between the presence of the fungal genus Neoascochyta and germination, while Pyrenophora and Alternaria species appeared positively associated with germination. Our results indicated some co-existence patterns between fungal species, including both pathogenic and non-pathogenic species, with some species combinations associated with the germination potential of wheat seed.
Abstract
No abstract has been registered