Effect of Day Length on Growth, Flowering, and Yield of Three Strawberry Varieties in a Tropical Climate

Light plays a vital role in plant growth and development, significantly affecting both the quality and quantity of strawberry fruit production. This study investigated the effects of day length on growth, flowering traits, and yield of selected strawberry cultivars by applying an environmental engineering approach. Conducted in a tropical greenhouse, the experiment involved supplemental LED lighting for three Japanese cultivars (‘Haruhi’, ‘KS75’, and ‘Sakura’). The findings revealed significant interactions between LED lighting and cultivar type in terms of growth parameters before and after fruiting. Specifically, crown height and crown diameter increased by 0.21 cm and 0.30 cm, respectively, under LED lighting. Compared to conventional (non-LED) lighting, LED exposure also resulted in reduced leaf temperature and plant height, by 1.37 ℃ and 2.58 cm, respectively. Flowering characteristics showed notable cultivar-specific responses to LED lighting. In ‘Sakura’, the number of flowers per plant and per bunch increased by 11.75 and 5.87, respectively. Furthermore, the cultivar ‘KS75’ exhibited significantly earlier flowering, by approximately 27 d, under LED treatment compared to non-LED conditions. While fruit yield characteristics did not show significant interactions between cultivars and lighting, independent statistical analysis indicated that ‘KS75’ produced the highest total yield (256.54 g), average fruit weight (9.88 g), fruit diameter (26 mm), and fruit dry weight (14.50 g). On the other hand, ‘Sakura’ had the highest number of fruits per plant, averaging 11.52 g per plant per month. These variations are attributed to the inherent genetic differences among cultivars. In conclusion, the application of LED lighting under a 12 h d length in tropical conditions significantly influenced specific growth and flowering traits in strawberry plants. ‘Sakura’ responded most favorably in terms of floral characteristics, whereas ‘KS75’ demonstrated superior performance in generative yield traits.