Mapping was performed in a population of 137 F6–8 recombinant inbred lines (RILs) developed from a cross of BTx623/IS3620C. BTx623 is an agronomically important inbred line that was derived from a cross between BTx3197, a kafir line, and SC170–6, a zera zera line. IS3620 C is a guinea line. It was originally collected in Gamjin, Nigeria, where it was known as ‘KO37 Canjin.’ The donor parent used for conversion of IS3620C to a short-day photoperiod was BTx406.

The BT×IS population has been mapped with a subset of 145 SSR/RFLP markers as previously described (Hart et al. 2001). The 145 BT×IS markers were a subset of a 2,926 marker high-density map (Bhattramakki et al. 2000; Menz et al. 2002). Additional 15 SSR and 17 new RFLP markers were mapped on the map as well. The marker and map data for this population are kindly provided by Drs. A. H. Paterson and F. A. Feltus.