Biology subjects

Witzell, J.

Publications and source records attributed to Witzell, J..

3 recordsLinked to original sources

bioRxiv2024

Evaluating the Biocontrol Potential of Pythium oligandrum and Serratia proteamaculans in Controlling Phytophthora plurivora in European beech (Fagus sylvatica)

In recent years, the plant pathogen Phytophthora plurivora has caused severe damage to beech forests in many European countries, including Sweden. In many affected areas, few protective measures are in place due to fears about potential negative impacts on the ecosystem or public health. The research presented in this article assesses the biocontrol potential of the oomycete Pythium oligandrum and the bacterium Serratia proteamaculans against P. plurivora, with experiments performed under both in vitro and greenhouse conditions, which could represent a step forward in developing a safe treatment for European beech forests. The in vitro results revealed that P. oligandrum and S. proteamaculans significantly inhibited pathogen growth and stimulated a shift in the hyphal growth pattern towards shorter, branched hyphae with many hyphal swellings and thickened cell walls. The experiments conducted in greenhouses showed that treating three-month-old beech seedlings with P. oligandrum and S. proteamaculans counteracts the P. plurivora pathogen and reduces disease symptoms on the aerial and underground parts of the plant. GC-MS analysis detected the volatile organic compounds alpha-pinene, 2,5-dimethyl-pyrazine, and 3-methyl-1-butanol from S. proteamaculans; these compounds have the potential to inhibit pathogen growth. The disease suppression demonstrated by these biocontrol agents could thus be related to the synergistic effect of competition for nutrients with the secretion of hydrolytic enzymes and VOCs; moreover, induced systemic resistance may be triggered under greenhouse conditions. In conclusion, using P. oligandrum and S. proteamaculans could represent an environmentally friendly strategy for effectively controlling the disease caused by P. plurivora in beech.

pathology↗

bioRxiv2020

Aspen leaves as a "chemical landscape" for fungal endophyte diversity - Can nitrogen and herbivory shape the community composition in controlled conditions?

AO_SCPLOWBSTRACTC_SCPLOWThe endophytic microbiome may influence the ecological performance of plants, including forest trees. Various abiotic and biotic factors may shape the endophyte communities directly but also indirectly, by modifying the quality of host plants as a substrate. We hypothesized that potentially antifungal or fungistatic condensed tannins (CTs) would determine the quality of aspen (Populus tremula) leaves as a substrate for endophytic fungi. By subjecting the plants to nitrogen fertilization (N) or herbivory (H; leaf beetles) we aimed to change the internal "chemical landscape", especially the CT levels, in aspen leaves. We expected that this would lead to changes in the fungal community composition, in line with the predictions of heterogeneity-diversity relationship hypothesis. To test this we conducted a greenhouse study where aspen plants were subjected to N and H treatments, individually or in combination. The chemical status of the leaves was analysed using GC/MS (114 metabolites), LC/MS (11 phenolics) and UV-spectrometry (CTs) and the endophytic communities were characterized using culture-dependent sequencing. Nitrogen treatment, alone or in combination with herbivory had a suppressing effect on the concentration and within-treatment variation in the CT precursors, catechins, and resulted in similar trend also in CTs. Nitrogen increased the concentration of certain amino acids, and it also tended to increase most of the analysed sugars sugars. Herbivory had a negligible effect on chemical traits. In N-treated plants, the endophyte richness and abundance were higher than in plants exposed to H, but in general, the diversity of the culturable endophytes remaind stable despite the subtle changes in leaf chemistry.

plant biology↗

bioRxiv2020

Structure of core fungal endobiome in Ulmus minor: patterns within the tree and across genotypes differing in tolerance to Dutch elm disease

Plants harbour a diverse fungal community with complex symbiotic interactions and significant roles in host physiology. However, the cues that steer the composition and structure of this community are poorly understood. Trees are useful models for assessing these factors because their large size and long lifespan give these ecosystems time and space to evolve and mature. Investigation of well-characterised pathosystems such as Dutch elm disease (DED) can reveal links between endomycobiome and pathogens. We examined the endophytic mycobiome across the aerial part of a landmark elm tree to identify structural patterns within plant hosts, highlighting not only commonalities but also the effect of local infections in some branches of the crown. We used a common garden trial of trees with varying levels of genotypic susceptibility to DED to identify associations between susceptibility and endomycobiome. Three families of yeasts were linked to higher DED tolerance: Buckleyzymaceae, Herpotrichiellaceae and Tremellaceae. Surveying a natural population with a gradient of vitality, we found some taxa enriched in declining trees. By combining all surveys and adding a further study in a distant natural population, we found evidence of a U. minor core mycobiome, pervasive within the tree and ubiquitous across locations, genotypes and health status.

microbiology↗