Fig. 3 (a) RAPD amplification of six bean parents used for the development of four segregating common bean populations including the RI populations of Venezuela 44 x BAC 6 (VB), Belneb RR-1 x A55 (BA), and BAC 6 x HT 7719 (BH) and the BC₂F₃ population of PC 50 x BAC 6 (PB). Key to individuals: lane 1 a 100-bp molecular weight ladder, lane 2 `A55', lane 3 `Belneb RR-1', lane 4PC 50, lane 5 `Venezuela 44', lane 6 `BAC 6', and lane 7 `HT 7719'. The arrow indicates the RAPD band with molecular weight of approximately 1250 base pair (BC409.1250) which is only amplified in resistant parents, BAC 6 and Belneb RR-1. (b) Primer specific amplification of the BC409.1250 polymorphism based on PCR primers designed from the sequence of the RAPD fragment