Characterisation of indigenous apple accessions with respect to polymorphism of ACS1 and ACO1 genes

Ethylene is the simplest signalling molecule with a hormone-like function that plays a major role in many developmental processes, including ripening of climacteric apple fruit. The allelic polymorphisms of ACS1 and ACO1 genes, encoding for ACC synthase and ACC oxidase, which catalyse the last two steps in the ethylene biochemical pathway, were analysed in nineteen indigenous apple accessions grown in individual growers' orchards in the regions of central and southwestern Serbia. A polymorphism was detected using the polymerase chain reaction (PCR) for the ACS1 gene and the additional enzymatic digestion of the PCR product with BamH1 and RsaI for the ACO1 gene. The ACS1-1 and ACS1-2 alleles of the ACS1 gene, as well as the a and c alleles of the ACO1 gene were identified. The polymorphisms observed upon PCRs and digestion with restriction enzymes were generated in two genotypes for both genes, i.e. the ACS1 gene - ACS1-1/1 and ACS1-1/2, and the ACO1 gene - aa and ac. Out of nineteen apple accessions, sixteen were homozygous for the allele ACS1-1 and three were heterozygous (ACS1-1/2); regarding the ACO1 genotype, fourteen were homozygous for the allele a and five were heterozygous (ac allelic constitution). The molecular survey in the current study provides an increase in the number of apple accessions with potential to be used as parents in breeding programmes, aiming to obtain high quality cultivars that retain fruit texture during long storage. Therefore, the heterozygous accessions for the ACS1 gene - 'J-LuN/1', 'Kraljica' and 'Šumatovka', may have an important position in future breeding programmes.