Examination of Maximilian Sunflower (Helianthus maximiliani Schrad.) Ideotypes with Restricted Branching.

Perennial grains have been suggested as a potential route for enhancing the sustainability of agricultural systems through the contribution of new crop ecosystem services. Efforts are underway to develop new perennial crops forms and breeding strategies for perennial grains and oilseeds follow two main paths: I: the perennialization of existing crops and II: the neo-domestication of wild perennial species.  The neo-domestication of wild species requires the development and identification of suitable plant ideotype models for agricultural production.

Maximilian sunflower (Helianthus maximiliani Schard.) is perennial wild crop relative of domesticated sunflower (Helianthus annuusL) and a candidate perennial oilseed species. Wild type morphotypes exhibit indeterminate flowering and extensive branching posing potential obstacles to crop maturity and mechanical harvest. Restricted branching and unihead morphotypes, which exhibit strong apical dominance and determinate flowering akin to domesticated sunflower, pose a potential ideotype for meeting these challenges. 

F₂ populations between wild and restricted branching morphotypes segregating for apical dominance were generated to examine genetic correlations between yield contributing traits and degree of apical dominance. Employing correlation and principal component analysis relationships were examined between variables including head diameter and head count, head diameter and plant height, branch length and branch count and interbranch length and flowering synchronicity.

Productivity per branch was estimated using average head diameter, head count and total branch count. The average potential seed output per branch expressed as (head diameter)(head count) is maximized at 5 branches per plant and decreases with the addition or loss or branches. This suggests the ideotype for determinate flowering Maximilian sunflower is a plant exhibiting a compact branching pattern with 5 branches to maximize seed production per branch while maintaining a degree of uniform flowering and maturity relative to the wild type.