Fourthly, our results indicated that parental selection is
critically important for the success of a BC breeding program.
While widely adaptable superior commercial lines should be
used as recurrent parents, the choice of donors of target traits
may bemore difficult. In this study, the japonica donor, C418 was
apparently a better donor than the two tropical indica donors
(IR64 and AT354) in contributing promising DT and HY progeny
in Hainan. This was surprising since none of the donors was superior for the target traits. In two separate experiments, we
found that indica donors tend to contribute more trait enhancing
alleles for DT and CT than japonica lines [16,22]. Thus,
exploiting the genetic diversity in the subspecific gene pools
using BC breeding will be of great importance for future genetic
improvement of complex traits in rice.