Anatomy and physiology of strawberry flowers determine fruit set

Commercial strawberry cultivars are often self-compatible, however most still depend on pollinators to achieve a marketable fruit set. To identify factors influencing fruit development in the absence of pollinators, this study examined the anatomical and physiological characteristics of flowers in four strawberry cultivars. The analyses focused on floral structure, pollen traits, and fruit outcomes. Micro-CT imaging was used to analyze floral morphology. Pollen quantity and viability were assessed using impedance flow cytometry. Mature viable pollen was quantified at 0, 1, 2, and 3 days after anthesis. Cultivars that produced heavier fruit with a higher ratio of fertilized achenes tended to exhibit a greater filament-to-receptacle height ratio and a shorter stamen-to-stigma distance. These traits were especially pronounced in cultivars with tall stamens positioned closer to the stigma. Additionally, greater pollen quantity and sustained pollen viability over time were positively correlated with fruit weight and the fertilized achene ratio across all stamen types. Despite these favorable traits, all fruit developed without pollinators showed signs of malformation. These deformities, along with reduced fertilized achene ratios, were linked to cultivar-specific anatomical and physiological limitations. The findings underscore the importance of supplemental pollination for achieving high-quality strawberry production in indoor vertical farming systems.