The current C32bc9 stock is a derivative of Steve Johnson's
inbred C32. (please note that this Johnson isolate of C32 is likely to be different than C32 stocks developed by Charline Walker at Oregon, due to differential assortment of haplotypes in different isolates of the stock and the finding that C32 was not completely inbred at the time the Johnson stock split from the Walker stock). Because Johnson's inbred C32 is currently not a vigorous line, we are in the process of introgressing genes for vigor into the inbred C32 genetic background. This is performed as follows.
Inbred C32 females from Johnson laboratory stocks were crossed to inbred SJD males, then the resulting hybrid females were backcrossed to inbred C32 males. Robust females were selected from progeny of this backcross and crossed again to inbred C32 males. Sequential backcrossing was repeated for a total of 9 generations; in each generation the most robust females were selected. After the ninth sequential backcross, we surveyed the stock with our first-pass mapping panel of SSLP markers (Rawls et al, 2003). This revealed that the stock at this generation still segregates with the SJD allele at more than 1/3 of its loci instead of the predicted ~0.5% of genomic markers with the residual SJD haplotype. The Johnson lab continues to backcrosses to reduce the SJD contribution. In the meantime the stock donated to the ZIRC may serve as the best representative of C32 for distribution.