Relationship among the Rate of Female Flowers, Dry Matter Production, and Fruit Yield in Long-term Zucchini (Cucurbita pepo L.) Production

Abstract

Zucchini is a unisexual plant that produces both male and female flowers, and the number of female flowers is higher in the upper node. Because the rate of female flower production increases over the long term, the number of fruits harvested and the yield can increase. Therefore, we investigated the relationship between the rate of female flowers, dry matter production, and fruit yield in long-term production over 168 days (from 7 Oct. 2020 to 24 Mar. 2021). The proportion of female flowers with nodes higher than the 40th was 86.2%, which was reduced to 67% or 50% by trimming the young female flowers. No significant difference in total dry matter production or the fraction of dry matter distributed to the fruit was observed between the untreated control and the 67% of female flower plants at the end of the experiment. The light extinction coefficient of the zucchini canopy was k = 1.05. The photosynthetically active radiation intercepted by the plants was estimated from the light extinction coefficient, leaf area index (LAI), and light use efficiency (LUE). The fresh fruit yield was the highest in the control plants and was 6.9 ± 0.2 kg·m⁻² at the end of the experiment. Although fresh fruit yield decreased in the 50% female-flower restricted plants, a difference in fresh fruit yield between the control and 50% female-flower restricted plants was not observed until 126 days after transplanting (DAT), i.e., 10 Feb. 2021. Therefore, the excess female flower rate in the upper node did not increase the fresh fruit yield under lower solar radiation. In this study, we estimated the values required to develop a model to predict fruit yield and a potential increase in yield during long-term zucchini production.