Identification of avirulent alleles of pathogen effector genes in UK Leptosphaeria maculans (phoma stem canker) populations

Project: Other

Project Details


Phoma stem canker, caused by the fungal pathogen Leptosphaeria maculans, is a damaging disease on oilseed rape in the UK and can cause yield losses up to 50% if the disease is not controlled (Fitt et al., 2011). Use of effective host resistance to control this disease is becoming ever more important. Resistance against L. maculans relies on major resistance (R) gene-mediated resistance and quantitative resistance (Delourme et al., 2006; Rouxel et al. 2003; Huang et al., 2015). R gene-mediated resistance to L. maculans is associated with a gene-for-gene interaction in which the product of a pathogen Avr gene (i.e. effector gene) is recognized by the product of a host R gene so that the pathogen is unable to infect the host (i.e. resistant reaction). Therefore, R gene-mediated resistance to L. maculans is single-gene race specific resistance that is effective in protecting plants only if the corresponding avirulent allele (of the Avr gene) is predominant in the local L. maculans population. R gene-mediated resistance against L. maculans is often rendered ineffective after 2-3 years due to L. maculans population changes from avirulent to virulent (Rouxel et al., 2003; Sprague et al., 2006). Therefore, detection and identification of new virulent races of L. maculans is crucial for effective deployment of R gene-mediated resistance. The proposed student bursary project will screen UK L. maculans populations from different regions for avirulent alleles of Avr genes.
1. Identification of Avr genes in L. maculans isolates from different regions: Isolates of L. maculans collected in autumn 2015 from different regions in the UK will be cultured to make conidial suspensions and to harvest mycelium for DNA extraction. The conidial suspensions will be used to inoculate a differential set of cultivars with known R genes to determine the virulent/avirulent alleles of the corresponding Avr genes. The DNA of each isolate will be used to amplify the virulent/avirulent alleles of the corresponding Avr genes for further investigation of mechanisms leading to changes from avirulent to virulent in L. maculans isolates.
2. Assessment of phoma stem canker severity in field experiments. To help the student understand the importance of the disease, the student will learn how to recognize the disease symptoms and assess the severity of stem canker in field experiments at 3 sites. Stems of cultivars with different resistance will be sampled for DNA extraction. Amount of L. maculans DNA in the stem samples will be quantified using qPCR to investigate the relationship between the pathogen biomass and severity of phoma stem canker.
Effective start/end date20/06/1631/12/16


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