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Thèse soutenue le 12 décembre 2013
Financement :  INRA (Contrat Jeunes Scientifiques)
encadrement : Alain Baranger & Bernard Tivoli

Résumé :

Mycosphaerella pinodes is the causal agent of ascochyta blight, one of the most damaging foliar diseases in pea. Only partial resistance is available which underlying mechanisms are still unknown. Previous work has shown the effect of plant and canopy architectural traits on epidemics development, as plant height and leaf area index.  Moreover QTL mapping studies showed co-localizations between QTL of partial resistance and QTL controlling earliness, plant height and aerial biomass. Our main objective is to consider the potential link between architectural traits and partial resistance genetic control. Our strategy was to (i) conduct QTL analysis in a recombinant inbred line population derived from a cross between JI296 (susceptible) and FP (partially resistant) for several architectural traits (plant height, stipule size, number of branches and number of internodes) under controlled and field conditions; (ii) to select and map genes known to control earliness, ramification, plant height, senescence and foliar characteristics in pea; (iii) to screen architectural pea mutants for their ability to reduce ascochyta blight epidemics phenotyped in controlled conditions. Our results showed two major genomic regions of co-localizations on linkage groups V and VI between QTL controlling partial resistance to M. pinodes and QTL involved in stipule size, that could correspond to the ones observed previously. In addition 11 genes controlling architectural traits were mapped.  Among them, Ago1 was mapped on linkage group VI close to one of the two genomic regions of QTL co-localizations identified. At last architectural mutants for ramification, wax production and earliness showed significantly different disease levels.