Abstract
Wild apples and their hybrids are valued as a source of genetic resistance to biotic and abiotic stress. Malus niedzwetzkyana is an endangered ornamental apple species endemic to Southeast Kazakhstan, the center of Malus domestication. To test the fire blight resistance of M. niedzwetzkyana, eight plant genotypes were inoculated with a local strain of Erwinia amylovora. The genotypes possess different genetic backgrounds, which was confirmed via SSR profiling. Four out of eight displayed moderate to severe symptoms of fire blight infection, while the three wild genotypes proved resistant. To search for the source of the resistance, the samples were tested for the presence of FBF7 QTL using SCAR markers, where seven genotypes tested positive for one of the markers (AE10-375) and one for the other (GE80-19). No correlation between resistance phenotype and FBF7 QTL was confirmed, indicating the source lies elsewhere. Developing detailed genetic and phenotypic profiles of wild apple species helps advance both the preservation efforts and marker-assisted selection in apple breeding.