Twenty-nine full-sib crosses were used in an in vitro adventitious shoot production trial with Pinusradiata D. Don. Analyses with four pairs of reciprocal crosses showed that seed-size effects are significant for seed weight prior to tissue culture and embryo weight after 6 days in vitro. However, no significant influence of initial seed size was found on any other interim tissue-culture trait or on final shoot production. Narrow-sense heritabilities, calculated using nine half-sib families each comprising two full-sib crosses, were high for most tissue culture traits. For number of shoots per embryo they were 0.53 ± 0.22 based on individuals and 0.94 based on family means. Subsets of the families used in the tissue-culture study were represented in two field trials. One included parents of 11 of the control-pollinated families, and one included offspring from 13 of the control-pollinated families. Nine families were common to both field trials. Pearson correlation coefficients were determined between each of 13 in vitro traits and six field characteristics measured in one trial and seven traits in the other trial (five traits in common between the two field trials). Almost all correlations were nonsignificant. The significant correlations found were fewer than the number to be expected by chance alone when calculating such a large number of correlations. Thus, this study provides no evidence for significant associations between the in vitro traits measured, including frequency of highly proliferative embryos and shoot production per embryo, and the field characteristics assessed, including diameter, straightness, malformation, branch habit, needle retention, percent acceptable stems, Dothistroma resistance, and pilodyn rating.
Adventitious Shoot Production from a Vireya Hybrid of Rhododendron
