Field investigation of consequences from the genetic modification resulting in the fire blight resistant cisgenic apple line C44.4.146

Apple cultivars resistant to diseases and pests can reduce the currently high chemical footprint of apple production. However, developing such cultivars by classical breeding is a challenging and lengthy process. The cisgenic approach can be used to amend a susceptible apple cultivar with apple-own resistance genes using genetic engineering. The cisgenic line C44.4.146 was generated by transferring the fire blight resistance gene FB_MR5 from Malus × robusta 5 to the susceptible cultivar ‘Gala Galaxy’. To assess whether unintended effects occurred during the generation of this line, a field trial was conducted over five years with trees of the cisgenic line C44.4.146 and multiple control cultivars. A total of 44 tree- and fruit-related traits were assessed and compared over several years in the field. No trait differed statistically significantly between C44.4.146 and its wild type, nor was outside the variation observed among the ‘Gala’ controls over all observation years. The effect of a diet amended with leaf powder of the different genotypes included in the field trial on the fitness of the arthropod decomposer species Drosophila melanogaster and Folsomia candida was also investigated. The leaf material of C44.4.146 did not adversely affect the survival, growth and fecundity of the two arthropods. Despite the fact that only a single cisgenic line was investigated, the results show that cisgenesis represents a good complementary approach to conventional breeding to develop high quality resistant cultivars.