Priming of Resistance-Related Phenolics: A Study of Plant-Associated Bacteria and Hymenoscyphus fraxineus

Abstract

European ash (Fraxinus excelsior) is highly affected by the pathogenic fungus Hymenoscyphus fraxineus in all of Europe. Increases in plant’s secondary metabolite (SM) production is often linked tol enhanced resistance to stress, both biotic and abiotic. Moreover, plant-associated bacteria have been shown to enhance SM production in inoculated plants. Thus, our hypothesis is that bacteria may boost ash SM production, hence priming the tree’s metabolism and facilitating higher levels of resilience to H. fraxineus. We tested three different ash genotypes and used Paenibacillus sp. and Pseudomonas sp. for inoculation in vitro. Total phenol (TPC), total flavonoid (TFC) and carotenoid contents were measured, as well as the chlorophyll a/b ratio and morphometric growth parameters, in a two-stage trial, whereby seedlings were inoculated with the bacteria during the first stage and with H. fraxineus during the second stage. While the tested bacteria did not positively affect the morphometric growth parameters of ash seedlings, they had a statistically significant effect on TPC, TFC, the chlorophyll a/b ratio and carotenoid content in both stages, thus confirming our hypothesis. Specifically, in ash genotype 64, both bacteria elicited an increase in carotenoid content, TPC and TFC during both stages. Additionally, Pseudomonas sp. inoculated seedlings demonstrated an increase in phenolics after infection with the fungus in both genotypes 64 and 87. Our results indicate that next to genetic selection of the most resilient planting material for ash reforestation, plant-associated bacteria could also be used to boost ash SM production.

Phenolic and Antioxidant Compound Accumulation of Quercus robur Bark Diverges Based on Tree Genotype, Phenology and Extraction Method

“…can produce different amounts of phenols, flavonoids, and photosynthesis pigments [ 31 ]. Furthermore, we observed the same tendencies in ash, spruce, and pine trees as well as blueberries and lingonberries [ 32 , 43 , 47 , 53 , 54 ]. All these examples align perfectly with the findings of this study, whereby we observed statistically significant differences in the amounts of TPC, TFC and antioxidant scavenging capacity diverging in different half-sib families grown in the same site and belonging to the same population.…”

High Variability of Fungal Communities Associated with the Functional Tissues and Rhizosphere Soil of Picea abies in the Southern Baltics

“…in Europe and is not associated with P. abies. The detection of H. fraxineus in different samples of the study was probably due to the presence of its propagules on the surface of different tissues (needles, shoots, or roots) and in the soil as the surface of our samples was not sterilised, and the disease caused by this fungus is active in the area [107]. The soil and tree roots were commonly colonised by mycorrhizal fungi (Table 4, Figure 7), which may also have limited the occurrence and activity of pathogenic fungi [108].…”

Genotype-Dependent Jasmonic Acid Effect on Pinus sylvestris L. Growth and Induced Systemic Resistance Indicators

“…It is worth noting that the five tested Pinus sylvestris half-sib families exhibited different responses to JA application. Previous related studies show that different genotypes from the same species can exhibit varied production of secondary metabolites, antioxidant activity and growth [ 15 , 16 ]. Similar variations were observed in Norway spruce as well [ 42 ].…”

“…Non-enzymatic antioxidants include ascorbate, glutathione and photosynthesis pigments, such as carotenoids [ 12 , 13 , 14 ]. Additionally, plant response indirectly could be indicated through other photosynthesis pigments (i.e., chlorophylls) [ 15 , 16 , 17 ].…”