Early-stage performance of cocoa clones relative to their progenitor ortets: implications for large-scale clone selection.

摘要

Clone development in cocoa is an essential step and a long-term goal in crop improvement programs. Selection theory suggests that ortet selection within high-yielding families will lead to development of productive clones. The present study aims to verify the relationship between clones and their progenitor ortets and source families for yield. Eight clones obtained from four families (two ortets per family) and five clones used as parents for these families were evaluated at two locations. Though a positive correlation for tree vigor was observed between the two locations, genotype x location interaction was indicated by rank changes for two of the 13 clones. A significant genetic correlation (r_g=0.76) was observed between vigor and yield. Ranking of ortets and of source families for yield was different from that of their descendant clones; ranking for vigor was, however, consistent between clones and progenitor ortets. Ortets that had high juvenile-stage vigor produced clones with the highest bean yields. Clones descended from the same family were similar in both vigor and yield, indicating that within-family genetic variances were low. The present results provided evidence that ortet selection for yield will be more effective in families where the progenitor clones combine good phenotypic value and favorable general combining ability for vigor and yield. Selecting within families based solely on the yield ranking of the families without considering these attributes of the progenitor clones will lead to less than expected genetic gains.