Killing two enemies with one stone? Genomics of resistance to two sympatric pathogens in Norway spruce

Abstract

Trees must cope with the attack of multiple pathogens, often simultaneously during their long lifespan. Ironically, the genetic and molecular mechanisms controlling this process are poorly understood. The objective of this study was to compare the genetic component of resistance in Norway spruce to Heterobasidion annosum s.s. and its sympatric congener Heterobasidion parviporum. Heterobasidion root‐ and stem‐rot is a major disease of Norway spruce caused by members of the Heterobasidion annosum species complex. Resistance to both pathogens was measured using artificial inoculations in half‐sib families of Norway spruce trees originating from central to northern Europe. The genetic component of resistance was analysed using 63,760 genome‐wide exome‐capture sequenced SNPs and multitrait genome‐wide associations. No correlation was found for resistance to the two pathogens; however, associations were found between genomic variants and resistance traits with synergic or antagonist pleiotropic effects to both pathogens. Additionally, a latitudinal cline in resistance in the bark to H. annosum s.s. was found; trees from southern latitudes, with a later bud‐set and thicker stem diameter, allowed longer lesions, but this was not the case for H. parviporum. In summary, this study detects genomic variants with pleiotropic effects which explain multiple disease resistance from a genic level and could be useful for selection of resistant trees to both pathogens. Furthermore, it highlights the need for additional research to understand the evolution of resistance traits to multiple pathogens in trees.

Integrative Pre-Breeding for Biotic Resistance in Forest Trees

“…GP may also go beyond pre-breeding efforts, and feedback on restoration optimization [84] and provenance characterization [85] (e.g., by predicting biotic resistance and yield) even across thousands of half-sib families that could hardly be tested at once in field and lab trials for pests and herbivore resistance [86]. Expectations within these half-sib families are likely similar to the ones previously discussed, which are as follows: (i) a nascent trend towards a more polygenetic architecture of the resistance, and (ii) the occurrence of pleiotropic genes in response to multiple biotic stresses despite the apparent absence of phenotypic correlations in the components of resistance [77].…”

“…A useful type of polygenic model, yet to be calibrated within an omnigenic framework [16], is genomic prediction (GP) [76]. Predictive breeding via GP allows assessing genetic estimated values (GEVs) for biotic stress resistance [77]. GP uses historical resistance data to calibrate marker-based infinitesimal additive predictive models [78], which provide a more comprehensive representation of a quantitative polygenic trait than traditional genetic mapping [79], a tendency that several biotic resistances have started exhibiting [80].…”

Genetic diversity of Norway spruce ecotypes assessed by GBS-derived SNPs

“…At present, the availability of genomic-based genotyping platforms offers vast opportunities to address specific Norway spruce research questions, such as identifying candidate genes associated with drought response 27 , wood formation 28 , disease resistance 29 , morphological characteristics 30 or local adaptations 31 .…”

Drought Stress Described by Transcriptional Responses of Picea abies (L.) H. Karst. under Pathogen Heterobasidion parviporum Attack

“…Rapid advancements in molecular research have provided insights into the Norway spruce-H. parviporum forestry pathosystem through various studies, such as pathogen characterization and detection [19], constructing gene expression libraries [20] and screening of resistant trees based on genetic components [21]. Norway spruce resistance against H. annosum s.l.…”

“…Norway spruce resistance against H. annosum s.l. is a quantitative trait [21][22][23] and is associated with several known genes (defense responses) with variation [21,24]. Signaling molecules are a group of plant secondary metabolites with a critical role in defense processes [25].…”