Conservation of Malus Niedzwetzkyana Dieck Ex Koehne Genotypes From Kazakhstan Resistant to Scab and Fire Blight Diseases

Abstract Southeast Kazakhstan is part of the center of origin and the natural habitat of wild apple trees. Wild apples and their hybrids are involved in domestic apple breeding as a source of resistance to biotic and abiotic stress. Malus niedzwetzkyana is a valuable endemic apple species included in the Red Book of Endangered Species of Kazakhstan. The present study evaluated 23 M. niedzwetzkyana genotypes from different populations for their resistance to scab and fire blight diseases using SCAR markers. We determined that all 23 genotypes contained a 430 bp resistance allele for marker OPB19, and 5 of them also had a 799 bp resistance allele identified by marker OPB18 for scab resistance. For fire blight, seven genotypes contained a 375 bp resistance allele and one genotype had a 397 bp resistance allele for the QTL FBF7 locus identified by markers AE10-375 and GE-8019, respectively. Eight genotypes with double resistance to scab and fire blight were selected for further in vitro amplification to develop a genetic pool for biodiversity preservation, apple breeding, and wild apple population revival, among other purposes. All in vitro regenerants were analyzed for the presence of apple chlorotic leaf spot virus, apple mosaic virus, apple stem grooving virus, apple stem pitting virus, and tomato ringspot virus. For each of the eight genotypes with double resistance, genetic profiles were developed based on 12 SSR markers. These genetic passports allow us to maintain the purity of the genetic pool and improve MAS in apple breeding.