Peroxidase isoenzyme genes in the identification of apple cultivars and Malus species

The peroxidase genotypes of 188 apple cultivars, rootstocks and Malus species were recorded. Four loci, PRX-2, PRX-3, PRX-4 and PRX-7 were involved including 15 alleles. Using this information a clear grouping of 83 cultivars, 46 rootstocks and 59 species was achieved through knowledge of the genetic basic of banding patterns, which consequently enabled secondary and inconsistent bands to be recognised and disregarded as relevant factors in identification. The possible selective advantage of the PRX-2e allele recognised in descendants of ‘Jonathan’ (PRX-2ce) is discussed. Triploid cultivars showed three different PRX-2 alleles including ‘Ashmead’s Kernel’ (PRX-2bce), providing further evidence of the triploid nature of this cultivar.