Association genetics of phenolic needle compounds in Norway spruce with variable susceptibility to needle bladder rust

Abstract

Key messageAccumulation of phenolic needle metabolites in Norway spruce is regulated by many genes with small and additive effects and is correlated with the susceptibility against fungal attack.AbstractNorway spruce accumulates high foliar concentrations of secondary phenolic metabolites, with important functions for pathogen defence responses. However, the molecular genetic basis underlying the quantitative variation of phenolic compounds and their role in enhanced resistance of spruce to infection by needle bladder rust are unknown. To address these questions, a set of 1035 genome-wide single nucleotide polymorphisms (SNPs) was associated to the quantitative variation of four simple phenylpropanoids, eight stilbenes, nine flavonoids, six related arithmetic parameters and the susceptibility to infection by Chrysomyxa rhododendri in an unstructured natural population of Norway spruce. Thirty-one significant genetic associations for the flavonoids gallocatechin, kaempferol 3-glucoside and quercetin 3-glucoside and the stilbenes resveratrol, piceatannol, astringin and isorhapontin were discovered, explaining 22–59% of phenotypic variation, and indicating a regulation of phenolic accumulation by many genes with small and additive effects. The phenolics profile differed between trees with high and low susceptibility to the fungus, underlining the importance of phenolic compounds in the defence mechanisms of Norway spruce to C. rhododendri. Results highlight the utility of association studies in non-model tree species and may enable marker-assisted selection of Norway spruce adapted to severe pathogen attack.Electronic supplementary materialThe online version of this article (doi:10.1007/s11103-017-0589-5) contains supplementary material, which is available to authorized users.

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

“…Pinus cembra) instead of P. abies in particular areas. In addition, UAV flights could facilitate the identification and GPS localization of trees with enhanced resistance for breeding programmes (Ganthaler et al ., , ), which would be cheaper than using helicopter flights. Application on entire forest stands and larger regions would require more cost‐intensive professional UAVs, georeferencing and alignment of images (Getzin et al ., ; Di Gennaro et al ., ; Haghighattalab et al ., ).…”

“…Image acquisition was conducted on the study site Praxmar im Sellraintal (Tyrol, Austria; 1680 m a.s.l., 47°09′N 11°08′E), located near the alpine timberline and characterized by typical subalpine Norway spruce forests, which were repeatedly infected and damaged in the last decade by C. rhododendri . Individual trees showing different disease severities and the occurrence of putative resistant trees (Mayr et al ., , ; Ganthaler et al ., ) offered ideal conditions for comparisons. Furthermore, 3‐year‐old plants from vegetative reproduction of spruce clones with varying susceptibility to C. rhododendri were available.…”

“…The values are based on a visual estimate and do not include indications of the extent of symptom development, which can vary considerably between individual years, sites and specimens (Ganthaler et al ., ; Zottele et al ., ). In several physiological and biochemical studies, disease severity of individual trees was estimated via a semiquantitative method (Oberhuber et al ., ; Ganthaler et al ., ); the percentage of current‐year needles with disease symptoms was evaluated by visual assessment and using a discrete disease scale with five classes between 0% and 100%. However, visual estimation is always subject to an individual's experience and reduces the repeatability (Bock et al ., ).…”

The Resistance of Scots Pine (Pinus sylvestris L.) Half-sib Families to Heterobasidion annosum

“…The TPC concentration comparison with susceptibility indicators (incidence rate, spread, and mortality) shows that the half-sib families with lower susceptibility were characterized by the ability to increase TPC after inoculation compared to the control group. The variation between different provenances and significant genetic regulation was reported for several stilbenes and flavonoids [41,[70][71][72]. Venäläinen et al [32] indicated that there are pronounced and significant differences in the concentration of individual stilbenes (PS and PSM) between the resistant and susceptible Scots pine hardwood of two progeny in Finland.…”

“…Some authors report that variation of plant secondary metabolites depends upon both genetic and environmental factors [39][40][41]. In coniferous trees, associations have been reported for several phenotypic traits, including wood properties [42][43][44][45], growth and wood chemistry [46], serotiny [47], carbon isotope discrimination [48,49], cold hardiness, and bud set timing [50,51], but rarely for cellular phenotypes (e.g., metabolite concentrations) [52] or disease resistance [53].…”