Identification of molecular and chemical markers that correlate with conifer resistance against root and stem decay pathogens (Heterobasidion annosum s.l.)

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Title: Identification of molecular and chemical markers that correlate with conifer resistance against root and stem decay pathogens (Heterobasidion annosum s.l.)
Author: Liu, Mengxia
Other contributor: Helsingin yliopisto, maatalous-metsätieteellinen tiedekunta
Helsingfors universitet, agrikultur-forstvetenskapliga fakulteten
University of Helsinki, Faculty of Agriculture and Forestry
Kasvitieteen tohtoriohjelma
Doktorandprogrammet i botanik
Doctoral Program in Plant Sciences
Publisher: Helsingin yliopisto
Date: 2022-08-19
Language: en
Belongs to series: URN:ISSN:2342-5431
Thesis level: Doctoral dissertation (article-based)
Abstract: Norway spruce (Picea abies Karst) and Scots pine (Pinus sylvestris L.) are ecologically and economically important conifer species. The root and stem rot pathogens Heterobasidion annosum s.l. lead to severe diseases throughout European forests, resulting in an annual loss of approximately 50 million euros in Finland. In addition to chemical and biocontrol approaches, the application of resistant genotypes generated through breeding will play a potential role in controlling and managing the diseases. However, our understanding of the genetic factors that contribute to conifer resistance against Heterobasidion spp. is quite limited. The aim of this study was to identify molecular and chemical markers that correlate with phenotypic variation in disease resistance. Initially inducible defense mechanisms underlying resistance were evaluated through inoculating Norway spruce plants at three developmental stages (seedlings, young trees and mature trees) with H. parviporum. For constitutive resistance study, short-term resistance screening was conducted using needles of Norway spruce and Scots pine sampled prior to Heterobasidion spp. infection. Based on sapwood lesion area, resistant and susceptible genotypes were identified. The results revealed that conifer trees could initiate multiple defense responses against pathogen attacks, including necrosis and lesion formation together with increased cell death, increase of pH and peroxidase activity, and the induction of defense-related genes. Furthermore, certain monoterpene and sesquiterpene compounds affected inherent resistance. Monoterpenes such as bornyl acetate, camphene and β-pinene, and several sesquiterpenes were highly concentrated in resistant Norway spruce trees. Scots pine trees with enhanced resistance showed higher contents of 3-carene, whereas susceptible trees had higher α-pinene concentrations. RNA sequencing analysis showed that the expression of genes involved in lignin and flavonoid biosynthesis might influence resistance to H. parviporum in Norway spruce. Transcripts relevant to the abiotic and biotic stress interactions exhibited the possibility to increase susceptibility to H. annosum in Scots pine. The results revealed that even if Norway spruce and Scots pine share some common pathways in defense against necrotrophic Heterobasidion spp. infection, subtle inherent differences exist in their chemical and transcriptome response profiles. The results provide additional insights to serve as the foundation for future studies on the resistance of conifer trees to root rot pathogens.Tiivistelmää ei ole saatavana.
Subject: forest pathology
Rights: Julkaisu on tekijänoikeussäännösten alainen. Teosta voi lukea ja tulostaa henkilökohtaista käyttöä varten. Käyttö kaupallisiin tarkoituksiin on kielletty.

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