Heritability estimates for callus growth and regeneration in desmodium

The F2 and F3 generations of two crosses (6123×13083 and 6123×144, 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 additive-dominant genetic model. Heritability estimates obtained from parent-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 F3 families exhibited much more vigorous and prolific regeneration than the regenerating parental genotype. Because many individuals in the segregating generations showed no evidence of regeneration, population distributions for this trait were severely truncated, or censored. Regression-order analysis was used to estimate means and variances of these censored populations. The association between poor callus growth and high regeneration capacity observed in the parental lines was absent from the F2 and F3 generations, indicating that no association between callus growth and regeneration was present.