Temperature is an important environmental factor influencing phenological development and productivity of sweet corn through heat unit accumulation. This study evaluated heat unit accumulation, heat use efficiency (HUE), yield components, and sweetness of seven commercial sweet corn cultivars grown under tropical lowland conditions during one growing season. The experiment was arranged in a randomized complete block design with seven cultivars and three replications. Heat unit accumulation was calculated using growing degree days (GDD) with a base temperature of 10°C. Phenological stages, plant height, cob yield components, total soluble solids (°Brix), and HUE were recorded. Significant differences among cultivars were observed in GDD required to reach vegetative emergence, tasseling, and silking, whereas GDD at the milk stage and HUE did not differ significantly. Exsotic F1 produced the highest cob weight with husk (354.88 g), cob weight without husk (264.16 g), cob length (20.37 cm), and cob diameter (60.27 mm), while Hibrix 72 F1 exhibited the highest total soluble solids (15.11 °Brix). Pcobson correlation analysis showed that HUE was positively associated with cob weight and cob size, whereas °Brix was negatively correlated with cob yield components. Principal component analysis separated cultivars according to phenological, yield, and quality traits. Under the environmental conditions of this study, commercial sweet corn cultivars differed in thermal requirements, yield characteristics, and sweetness, providing comparative information on cultivar performance under tropical lowland conditions.
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