Abstract
Lack of resistance to pink snow mould (Microdochium nivale) is a major constraint for adaptation of perennial ryegrass (Lolium perenne L.) to continental regions with long-lasting snow cover at higher latitudes. Almost all investigations of genetic variation in resistance have been performed using cold acclimated plants. However, there may be variation in resistance mechanisms that are functioning independently of cold acclimation. In this study our aim was to identify candidate genes involved in such resistance mechanisms. We first characterized variation in resistance to M. nivale among non-acclimated genotypes from the Norwegian cultivar ‘Fagerlin’ based on relative regrowth and fungal quantification by real-time qPCR. One resistant and one susceptible genotype were selected for transcriptome analysis using paired-end sequencing by Illumina Hiseq 2000. Transcriptome profiles, GO enrichment and KEGG pathway analysis indicate that defense response related genes are differentially expressed between the resistant and the susceptible genotype. A significant up-regulation of defense related genes, as well as genes involved in cell wall cellulose metabolic processes and aryl-alcohol dehydrogenase (NADP+) activity, was observed in the resistant genotype. The candidate genes identified in this study might be potential molecular marker resources for breeding perennial ryegrass cultivars with improved resistance to pink snow mould.
Highlights
Lack of resistance to pink snow mould (Microdochium nivale) is a major constraint for adaptation of perennial ryegrass (Lolium perenne L.) to continental regions with long-lasting snow cover at higher latitudes
Under gene ontology (GO) term actin nucleation, we found that genes encoding actin-related protein 2 (ARP2), importin-βand serine threonine-protein kinase (TOR) were over-represented in the R genotype during infection
Fagerlin were found to be significantly different in resistance, as measured by relative regrowth, and accumulation of M. nivale DNA, as quantified by real-time qPCR
Summary
Lack of resistance to pink snow mould (Microdochium nivale) is a major constraint for adaptation of perennial ryegrass (Lolium perenne L.) to continental regions with long-lasting snow cover at higher latitudes. The fungus Microdochium nivale (Fr.) Samuels & Hallet is considered to be the most widespread cause of biotic winter injury in these crops[4] It is an opportunistic species causing pink snow mould on winter cereals, turf and forage grasses at low temperatures, with or without a snow cover. Resistance to pink snow mould is enhanced by cold acclimation[2,3,4] During this process the plant undergoes numerous physiological and bio-chemical changes which are essential for winter survival[7]. Genetic variation in cold-induced resistance to pink snow mould in triticale has been shown to be associated with changes in physical and chemical properties of the leaf surface and cell walls[9], and with photosynthetic acclimation and peroxidase activity[10]. Inherent resistance that is independent of cold acclimation may be more specific to M. nivale than cold-induced disease resistance, and is likely to be important for preventing diseases caused by M. nivale during the growing season, such as microdochium patch and leaf www.nature.com/scientificreports/
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