A randomly amplified polymorphic DNA (RAPD) marker tightly linked to the scab-resistance gene V(f) in apple

Almost 200 random sequence decamer primers were used to screen a pair of bulked samples of apple (Malus x domestica Borkh.) DNA and that of the donor parent Malus floribunda Sieb. clone 821 for molecular markers linked to the V(f) gene conferring resistance to apple scab [Venturia inaequalis (Cke.) Wint.]. Identified was a single primer that generated a polymerase chain-reaction (PCR) fragment, OPAR4/1400, from the donor parent M. floribunda clone 821 and the scab-resistant selections/cultivars bulk, but not from the scab-susceptible recurrent-parent bulk. Cosegregation analysis using a segregating apple progeny and polymorphism analysis of individual scab-resistant selections/cultivars confirmed that this marker was linked to the scab-resistance gene V(f). OPAR4/1400 was then cloned and sequenced. Sequence-specific primers of 25 oligonucleotides based on the marker were developed and used to screen further M. floribunda clone 821, scab-susceptible apple cultivars, scab-resistant apple cultivars, and scab-resistant Purdue, Rutgers, and Univ. of Illinois apple breeding program selections. The sequence-specific primers identified polymorphisms of OPAR4/1400 based on the presence or absence of a single band. This molecular marker is at a distance of about 3.6 cM from the V(f) gene.