Dry Matter Production and Fruit Sink Strength Affect Fruit Set Ratio of Greenhouse Sweet Pepper

Abstract

We investigated the relationships among the fruit set, dry matter production, and source-to-sink ratio of sweet pepper (Capsicum annuum) plants grown in a greenhouse. We quantified daily fruit sink strength per stem (st) at m days after transplanting (SSTm_st) by modeling the fruit growth curve. The daily total dry matter production (TDMm_st) was calculated and defined as the source strength. During an experiment lasting ≈250 days, the fruit set ratio [number of fruit harvested/number of flowers (FSRm)] decreased significantly with increases in both the weekly average SSTm_st from 9 days before anthesis (DBA) to 13 days after anthesis (DAA) and the weekly average fruit number (FRNm_st) from 9 to 1 DBA. FSRm increased significantly with increases in both the weekly average TDMm_st from 1 to 13 DAA and the weekly average source-to-sink ratio [source strength/fruit sink strength (SSRm_st)] from 5 DBA to 13 DAA. During the whole experimental period, significant positive correlations with FSRm were observed for TDMm_st and SSRm_st, and significant negative correlations with FSRm were observed for SSTm_st and FRNm_st. FSRm increased until approximately the time when the weekly average SSRm_st at 1 to 7 DAA (anthesis to 156°C⋅d−1) ranged from 1.0 to 4.0; then, it showed a saturation curve at SSRm_st values more than 4.0 (R2 = 0.81). These results suggest that it is possible to moderate the fluctuations in sweet pepper yield by monitoring the SSRm_st and the number of fruit set.

Modeling Short-term Yield Changes in Sweet Pepper Based on Dry Matter Production and Fruit Growth

“…6). Daily dry matter partitioning to fruits also cyclically fluctuated during cultivation (Homma et al 2022(Homma et al , 2024. The peaks and troughs of fresh weight yields were accurately predicted for model 2, but not for model 1, during this experiment.…”

“…Fluctuations in the fresh weight yield of sweet pepper have been reported to be closely related to the following three major factors: assimilate supply (Homma et al 2022), fruit load (Wien et al 1989), and fruit size (Wubs et al 2009b). During this study, the assimilate supply was calculated as the production of the total dry matter by considering the yield components (Eqs.…”

“…Similar to other horticultural crops such as tomato (Solanum lycopersicum) and cucumber (Cucumis sativus), sweet pepper is characterized by large fluctuations in the fruit set and fresh weight yields (Higashide 2009;Marcelis 1994;Marcelis et al 2006). For sweet pepper, this might be closely related to the cyclic fluctuation in dry matter partitioning to vegetative and generative organs (Homma et al 2022(Homma et al , 2024. Additionally, the number of peaks and amplitude of fluctuations in fresh weight yields are different in cultivars with different fruit sizes (Wubs et al 2009b).…”

“…For randomly selected plants in each plot at 0 DAT (a total of 8 plants of 'Nagano', 'Nesbitt', and 'Trirosso' and 12 plants of 'Artega'), the dates of anthesis and abortion at each node on the main stem during 0 to 230 DAT were continuously recorded twice per week. The dates of anthesis were defined as the days when the petals had completely opened, and pollen was considered to have been produced (Homma et al 2022;Wubs et al 2011). Mature fruits of the selected plants were regularly harvested once or twice per week until the end of cultivation; then, fruit fresh and dry weights (g/fruit) of each fruit were measured.…”

“…Large fluctuations in fruit set and fresh yield are issues associated with the production of sweet pepper (Capsicum annuum), even when plants are grown in optimal environments (Homma et al 2022;Ma et al 2011). This phenomenon is called flush, and alternating high and low fresh yields are caused by high and low fruit sets, respectively (Abdel-Mawgoud et al 2008;Al-Halimi and Moussa 2015;Heuvelink et al 2004).…”