Identification and mapping of markers for resistance to apple scab from 'Antonovka' and 'Hansen's baccata #2'

Bulked segregant analysis identified several RAPD markers that display close linkage to the genes identified as V-a (from 'Antonovka' PI 172633) and V-b (from 'Hansen's baccata #2') that confer resistance to apple scab. B398(480) was the closest marker segregating with the resistance response from descendants of 'Antonovka' PI 172633 and UBC220(700) was the closest marker for resistance from 'Hansen's baccata #2'. V-a and V-b were found to share flanking markers with each other and with the V-f resistance gene from Malus floribunda 821 and map to the same region as V-f on linkage group 8 of 'Rome Beauty' x 'White Angel'. Our study emphasizes the importance of determining the clone to be used in breeding and the need for further allelism tests involving 'Antonovka', 'Hansen's baccata #2', 'Hansen's baccata jackii', and other lesser known sources of resistance. These studies are needed to determine whether resistance from 'Antonovka' and 'M. baccata #2' is distinct from that of V-f and whether they can be used in breeding for more durable resistance.