The F-2 and F-3 generations of two crosses (6123 x 13083 and 6123 x 14
4, with 6123 the regenerating parent) were evaluated for callus growth
and regeneration capacity. Based on joint scaling tests and variance
partitioning, neither callus growth nor regeneration fitted a simple a
dditive-dominant genetic model. Heritability estimates obtained rom pa
rent-offspring regression analyses ranged from 0.65 to 0.77 for callus
growth and from 0.19 to 0.46 for regeneration, with the range in both
influenced by the cross and numerical scale employed, Members of two
F-3 families exhibited much more vigorous and prolific regeneration th
an the regenerating parental genotype. Because many individuals in the
segregating generations showed no evidence of regeneration, populatio
n distributions for this trait were severely truncated, or censored. R
egression-order analysis was used to estimate means and variances of t
hese censored populations. The association between poor callus growth
and high regeneration capacity observed in the parental lines tvas abs
ent from the F-2 and F, generations, indicating that no association be
tween callus growth and regeneration was present.