A new approach for early selection of short juvenile period in olive progenies

The purpose of this study was to evaluate the relationship between two types of vigor and architectural parameters (quantitative and qualitative) and the duration of juvenile period in olive and to test the effectiveness of three different strategies for an early elimination of seedlings with long juvenile period. Architectural parameters were evaluated in 794 one-year-old olive seedlings, and first flowering time for each seedling was then recorded the following three years. Among the quantitative parameters, 'Plant height' and 'Secondary shoots insertion angle' were those most correlated with the juvenile period duration. Among the qualitative parameters, 'Main vertical axis', 'Branching system', 'Preferential distribution of long shoots', 'Extreme leaf size', 'Branch orientation' and 'Branch bending' were also able to distinguish seedlings with different juvenile period duration. Four architectural types (defined on the basis of the qualitative parameters evaluated) were found in higher percentages in seedlings with short juvenile period. Finally, three new selection strategies based on the 'Branch orientation' (strategy I), the established architectural types (strategy II), and the association of 'Plant height' with architectural type (strategy III) all provided greater capacity for discarding seedlings with long juvenile period than did using only 'Plant height' method, the early selection criterion currently used for that purpose in breeding programs. The strategy based on combining a quantitative criterion (i.e. 'Plant height') and the qualitative architectural types, provided the most promising results from a practical point of view considering both ease of measurement and selection effectiveness.

Automated summary

This study evaluated the relationship between architectural parameters and vigor types in olive seedlings, finding that certain architectural types were more prominent in seedlings with short juvenile periods. Three selection strategies based on combining quantitative and qualitative parameters were more effective in early elimination of seedlings with long juvenile periods compared to using only height as a selection criterion.