A genomic remnant of Malus floribunda clone 821 introgressed into the
cultivated apple M. x domestica Borkh. was identified using randomly a
mplified polymorphic DNA (RAPD) markers obtained by the polymerase cha
in reaction (PCR). Using a set of 59 oligonucleotide decamer primers,
polymorphic DNA markers were identified among three pooled DNA samples
. Based on the presence or absence of bands among bulked apple scab-re
sistant selections and cultivars, bulked scab-susceptible cultivars, a
nd a M. floribunda clone 821 sample, one primer, A15, identified ampli
fied fragments in the scab-resistant bulked sample that was also uniqu
e to the M. floribunda clone 821. The unique band from M. floribunda c
lone 821 was amplified in four out of 17 scab-resistant selections/cul
tivars. This RAPD, designated OA15(900), identifies an introgressed fr
agment that has as yet no known function.