Foliar Phenolic Compounds in Norway Spruce with Varying Susceptibility to Chrysomyxa rhododendri: Analyses of Seasonal and Infection-Induced Accumulation Patterns

Abstract

Secondary phenolic metabolites are involved in plant responses to various biotic stress factors, and are apparently important for the defense against fungal pathogens. In this study, we investigated their role in defense against the rust Chrysomyxa rhododendri in Norway spruce. The fungal pathogen undergoes a seasonal lifecycle with host shift; after overwintering in rhododendron shrubs, it attacks the sprouting current-year spruce needles and causes needle fall in autumn. Repeated infections lead to reduced timber yield and severe problems with rejuvenation in subalpine Norway spruce forests. Trees with varying susceptibility to infection by C. rhododendri were selected and foliar phenolic composition was assessed using UHPLC-MS. We report on seasonal accumulation patterns and infection-related changes in the concentrations of 16 metabolites, including flavonoids, stilbenes, simple phenylpropanoids and the precursor shikimic acid, and their correlation with the infection degree of the tree. We found significant variation in the phenolic profiles during needle development: flavonoids were predominant in the first weeks after sprouting, whereas stilbenes, picein and shikimic acid increased during the first year. Following infection, several flavonoids and resveratrol increased up to 1.8 fold in concentration, whereas picein and shikimic acid were reduced by about 70 and 60%, respectively. The constitutive and early stage infection-induced concentrations of kaempferol, quercetin and taxifolin as well as the late stage infection-induced concentrations of stilbenes and picein were negatively correlated with infection degree. We conclude that a combination of constitutive and inducible accumulation of phenolic compounds is associated with the lower susceptibility of individual trees to C. rhododendri. The potentially fungicidal flavonoid aglycones may limit hyphal growth and prevent development of infection symptoms, and high levels of stilbenes may impede the infection of older needles. The presented results underline a highly compound-specific seasonal accumulation and defense response of Norway spruce and may facilitate the selection of promising trees for breeding programs.

In Vivo Antimicrobial and Wound-Healing Activity of Resveratrol, Dihydroquercetin, and Dihydromyricetin against Staphylococcus aureus, Pseudomonas aeruginosa, and Candida albicans

“…The combination of Resveratrol and benzoyl peroxide showed a high initial antibacterial activity and sustained bacterial growth inhibition. Some authors reported that the concentrations of Resveratrol and some other phenolic compounds (kaempferol, quercetin, taxifolin, other stilbenes, and picein) in Picea abies (Norway spruce) change upon rust infection with Chrysomyxa rhododendri (class Pucciniomycetes) and increase plant resistance to phytopathogens [17].…”

Sprouts and Needles of Norway Spruce (Picea abies (L.) Karst.) as Nordic Specialty—Consumer Acceptance, Stability of Nutrients, and Bioactivities during Storage

“…The sprouts are especially rich in vitamin C and minerals [ 2 , 4 , 5 ]. The sprouts also have high contents of secondary metabolites such as flavonoids (e.g., kaempferol, quercetin, isorhamnetin, and myricetin), condensed tannins, stilbenes, and terpenoids [ 2 , 5 , 6 , 7 , 8 , 9 ]. Due to the richness of vitamin C and phenolics, sprouts and needles have shown antioxidative activity [ 9 , 10 , 11 ].…”

Using image analysis for quantitative assessment of needle bladder rust disease of Norway spruce

“…This may explain the discrepancy between needle counting and image analysis (slope of the linear relationship, b < 0.8) and may contribute to the deviation of individual values from linear regressions. However, the needle area with distinct symptoms may be a better reference value for physiological analyses like measurements of photosynthesis, biomass production, secondary compound accumulation and pathogen defence reactions (Oberhuber et al ., ; Plattner et al ., ; Ganthaler et al ., ), and may be more representative for estimations of the quantitative resistance of trees against needle bladder rust. Moreover, the determined slope of the linear regressions permits the comparison and conversion of values gained with one of the two methods.…”

“…During August, aeciospores are released and again infect rhododendron plants, while spruce needles with disease symptoms are shed by the tree at the end of summer. Infections by C. rhododendri can cause the loss of up to 90% of the current‐year foliage, as reported for subalpine spruce forest in Tyrol, Austria for the years 2011, 2012 and 2015 (Ganthaler et al ., ). Repeatedly attacked trees show several distinct anatomical, morphological and physiological modifications, such as reduced chlorophyll content and reduced net photosynthesis of the needles, diminished biomass accumulation by all plant organs, and lower annual ring width and height increment (Ganthaler et al ., ).…”