Effect of phenology on susceptibility of Norway spruce (Picea abies) to fungal pathogens

Abstract

Ceratocystis polonica and Heterobasidion parviporum are important fungal pathogens in Norway spruce (Picea abies). Tree susceptibility to these pathogens with respect to phenology was studied using artificial fungal inoculations at six stages of bud development, and assessed by measuring phloem necroses in the stems of 2-and 8-year-old trees. Tree capacity for resistance was assessed by measuring phloem nonstructural carbohydrates at each stage. Phloem necroses were significantly larger in trees with fungal versus control inoculations and increased significantly over time. Changes in nonstructural carbohydrates occurred in the trees; a significant decline in starch and a slight but significant increase in total sugars occurred over time. These results suggest that susceptibility to fungal pathogens and carbohydrate levels in the stems of the trees were related to fine-scale changes in bud development. A trade-off may occur between allocation of starch (the major fraction of the stem carbohydrate pool) to bud development ⁄ shoot growth versus defence of the stem. Previous tests of plant defence hypotheses have focused on herbivory on plants growing under different environmental conditions, but the role of phenology and the effect of pathogens are also important to consider in understanding plant resource allocation patterns.

Genetic variation, inheritance patterns and parent–offspring relationships after artificial inoculations with <i>Heterobasidion parviporum</i> and <i>Ceratocystis polonica</i> in Norway spruce seed orchards and progeny tests

“…The heritability is somewhat lower than the estimates found for flushing scores in other progeny tests (e. g. Hannerz et al 1999;Skrøppa and Steffenrem 2015). The observed genetic correlation between the timing of flushing and C. polonica lesion lengths corresponds to what was found by Krokene et al (2012) who concluded that the level of susceptibility to this pathogen is related to tree phenology.…”

“…C. Moreau) has not been conducted, both due to limited information about genetic variation in resistance to the fungi and due to lack of reliable selection techniques. During the last 20 years several studies have demonstrated the presence of a genetic component in susceptibility to Heterobasidion, based on variation in lesion lengths after stem inoculation with the fungus Stenlid 1996, 1997;Swedjemark and Karlsson 2004;Swedjemark et al , 2001Arnerup et al 2010;Krokene et al 2012;Skrøppa et al 2014). Most of these studies were based on differently aged clonal material.…”

Genetic parameters for wood quality traits and resistance to the pathogens Heterobasidion parviporum and Endoconidiophora polonica in a Norway spruce breeding population

“…data). The seasonal growth rhythm stage at the time of inoculation, indicated by the phenology of apical meristems, is known to influence the results and could cause differences in observed variances and GxE interactions (Krokene et al 2012;Skrøppa et al 2015b;Swedjemark and Stenlid 1996). This vulnerability to environmental factors acting on the inoculum batch itself, or the trees tested, makes it important to design studies that include more than one test site, both parents and offspring, or different inoculum, to obtain an estimate of the repeatability of the results.…”

Defence reactions of mature Norway spruce (Picea abies) before and after inoculation of the blue-stain fungus Endoconidiophora polonica in a drought stress experiment

“…Inoculation of E. polonica is a frequently applied method for testing the capacity of trees to avert biotic invaders and to mobilise defences (Lieutier et al 2003;Krokene et al 2012). The long co-evolution of this pathogen with Norway spruce is substantiated by local and systemic induction of resistance marker genes in response to infection (Fossdal et al 2012).…”