Practical DNA markers to Estimate Apple (Malus x domestica Borkh.) Skin Color, Ethylene Production and Pathogen Resistance

Abstract

Determination of agronomically important traits with DNA markers in genetically segregating populations is a key to high-throughput breeding of apple trees. In the present report, we first estimated usefulness of four PCR-based DNA markers of apple in a set of 22 apple cultivars, which include popular cultivars in Japan such as ‘Fuji’, ‘Orin’, and ‘Shinano Gold’. The four DNA markers are reported to determine fruit storage life (ethylene production), fruit skin color, Alternaria resistance, and scab resistance. The target genes/locus of these DNA markers are MdACS1 gene, MdMYB1 gene, MdAlt locus, and MfVf gene. The types of these DNA markers are SSLP, dCAPS, allele-specific, and gene-specific, thus the markers were designated MdACS1-SSLP, MdMYB1-dCAPS(BstEII), MdAlt-AS, and MfVf-GS, respectively. DNA band patterns after gel electrophoresis were reasonable and consistent with previous reports for MdACS1-SSLP and MfVf-GS markers. On the contrary, band patterns of the MdAlt-AS marker were not necessarily consistent with Alternaria tolerance of the apple cultivars. It was also quite difficult to determine genotypes from the band patterns of the BstEII-based dCAPS marker MdMYB1-dCAPS(BstEII). Attachment of DS6 adaptor sequence to the forward primer improved genotype determinations, by making clear difference between the sizes of allelic DNA bands. Further improvement of this DNA marker was also achieved by the MdMYB1-CAPS(PmlI) marker, which is a PmlI-based CAPS marker. MdMYB1 genotypes determined by the MdMYB1-CAPS(PmlI) marker was consistent with apple skin colors and their genetic segregations.