An important goal of apple breeding is the introduction of disease resistance in new varieties to reduce pesticide use in apple production. Such resistances are often found in wild apple relatives, but their introgression into new cultivars by classical breeding cannot be achieved rapidly. Cisgenesis however offers the possibility to improve market-established apple cultivars with same species resistance genes. Our work aims at investigating the first cisgenic fire blight resistant apple line (C44.4.146), carrying the FB_MR5 resistance gene of Malus × robusta 5, under field conditions. C44.4.146 is compared to its wild type Gala Galaxy to uncover if the obtained resistance or the transformation process affected important tree or fruit properties of the cultivar. The results are evaluated in the context of natural variation found in selected somatic mutants of 'Gala' (e.g. 'Royal Gala'), which are grown in the same plot. Our study includes the analysis of several agronomic and phenotypic parameters of C44.4.146 (tree, flower and fruit characteristics), as well as its molecular characterization using a multi-omics (DNA, RNA, proteins and metabolites) approach. We are also evaluating potential effects of a diet supplemented with leaf powder of C44.4.146 on selected arthropods. Finally, we verify if the previously observed fire blight resistance from shoot inoculation experiments is also observed when the trees are inoculated through the flowers. The design of the experiment, the conditions under which the field trial was conducted, and preliminary results of phenotypic evaluations in the field are presented. This project will provide evidence-based data to support discussions on cisgenesis in our agricultural food systems.
