Characterization of polyploidy in the resistance to Venturia inaequalis in susceptible and monogenic resistant Malus x domestica Borkh.Ilnikar, Kristina (Avtor) Štajner, Nataša (Mentor) De Storme, Nico (Komentor) PolyploidyMalus domesticaVenturia inaequalisapple scabplant resistancedifferential gene expressionApple (M. x domestica), belonging to Rosaceae family, is the third most important fruit worldwide in terms of production and consumption. During the growing season, apple is infected by Venturia inaequalis, causing apple scab, one of the most destructive disease in apple culture. The main approach for controlling this disease is by multiple fungicide applications, which has resulted in resistance of the fungus to various fungicides. One of the potential alternative strategies with improved resistance to apple scab could be growing polyploid apple cultivars. In several cases, polyploids were recognized as more resistant to different types of stress than their diploid counterparts. The main goal of this thesis is to test the effect of polyploidy on phenotypic resistance and expression of defense-related genes and genes involved in the synthesis of phenolic compounds in di- and tetraploid apple varieties ‘Gala’ (scab-susceptible) and ‘Makali’ (monogenic resistant) during infection with V. inaequalis races 1 and 6. During the inoculation process, chlorosis, necrosis and sporulation were visually evaluated according to Chevalier method, and quantification of the fungal DNA qPCR was performed. The severity of evaluated symptoms and concentration of fungal DNA were on average lower in tetraploid than in diploid variants. For gene expression, RT-qPCR was performed. Polyploidy significantly affected the expression of PR-2(b), MPK4, PAL, NCS, F4R and LR in ‘Gala’ and of PR-1, CERK1, NCS, LR and 4CL in ‘Makali’. CDPK, WRKY29, PR-2(a), F3H and CCoAMT were not affected by ploidy.[K. Ilnikar]20202020-08-30 07:15:22Magistrsko delo/naloga118673UDK: 634.11:631.527.7:631.524.86:632.4(043.2)VisID: 178705COBISS_ID: 27186435sl