Quantitative and qualitative plant-pathogen interactions call upon similar pathogenicity genes with a spectrum of effects
Résumé
Septoria leaf blotch is a foliar wheat disease controlled by a combination of plant genetic resistances and fungicides use. R- gene-based qualitative resistance durability is limited due to gene-for-gene interactions with fungal avirulence ( Avr ) genes. Quantitative resistance is considered more durable but the mechanisms involved are not well documented. We hypothesize that genes involved in quantitative and qualitative plant-pathogen interactions are similar. A bi-parental population of Zymoseptoria tritici was inoculated on wheat cultivar ‘Renan’ and a linkage analysis performed to map QTL. Three pathogenicity QTL, Qzt-I05-1, Qzt-I05-6 and Qzt-I07-13 , were mapped on chromosomes 1, 6 and 13 in Z. tritici , and a candidate pathogenicity gene on chromosome 6 was selected based on its effector-like characteristics. The candidate gene was cloned by Agrobacterium tumefaciens -mediated transformation, and a pathology test assessed the effect of the mutant strains on ‘Renan’. This gene was demonstrated to be involved in quantitative pathogenicity. By cloning a newly annotated quantitative-effect gene in Z. tritici that is effector-like, we demonstrated that genes underlying pathogenicity QTL can be similar to Avr genes. This opens up the previously probed possibility that ‘gene-for-gene’ underlies not only qualitative but also quantitative plant-pathogen interactions in this pathosystem.
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