S03 - Session O1 - Factors limiting seed yields in hybrid carrot

Authors: Alistair Gracie *, Angus Dunbabin, Amy Lucas, Joanna Jones, Cameron Spurr

Hybrid carrot seed yields vary substantially. The causes of this variation in seed yield among carrot seed parent lines are not well understood. In this study, six commercial inbred lines were used; three pollen-donor 'male' lines and three male sterile 'female' lines. The carrot lines were selected to provide a wide range in seed yield based on prior commercial knowledge. Three commercial production sites located approximately 3km apart were used and a single male genotype and the three 'female' genotypes were grown at each site in a randomised design to create 9 separate hybrids. Key phases of pollination and fertilisation were studied in detail. We provide evidence that seed set and yield are predominantly controlled by the male sterile line (female line) in a hybrid carrot seed system. Post pollination, the female line had the greatest effect on seed set and that this effect was largely due to its role in governing pollen tube growth down the style independent of the male pollen line. This conclusion was based on controlled hand pollination experiments where different male genotype pollen was applied in similar quantiles and quality to the female genotypes.