Effects of different cultivation times on the marketable cob yield and quality of sweet corn cultivars

This study was conducted in 2022 and 2023 to examine the yield and quality characteristics of 17 different registered sweet corn (Zea mays L. saccharata) cultivars, including 14 with the sh2 gene and 3 with the su1 gene, under the conditions of Bilecik. The experiment was carried out in a randomized complete block design with split plots and three replications. The main crop sowing was conducted in early May, while the second crop sowing was performed in July after wheat harvest. The harvesting process of the cultivars used in the study was carried out separately for each cultivar by applying the finger test. All the traits examined in the study were significantly affected by cultivar, year × cultivar, and sowing time × cultivar interactions. The sucrose and total sugar contents of all cultivars carrying the sh2 gene were found to be higher than those of cultivars carrying the su1 gene. In contrast, the non-resistant and total starch contents of cultivars with the su1 gene were higher than those of all cultivars with the sh2 gene. Except for the sh2-carrying SF-1379 cultivar, all cultivars with the sh2 gene had a higher protein content and a lower soluble solid content than those with the su1 gene. In terms of husk-free fresh ear yield, the cultivars ranged between 1492.68 and 2494.49 kg da-1, with the lowest yield obtained from the Caramelo cultivar and the highest from the Sherbet F1 cultivar. The fresh kernel yield varied between 894.50 and 1634.11 kg da-1, with the lowest and highest yields observed in the Caramelo and Sherbet F1 cultivars, respectively. The soluble solid content ranged from 13.38 to 20.37° Brix, with the highest value in Sherbet F1 and the lowest in Vega-F1. The fructose content varied between 3.15 and 11.26 mg g-1, with the highest value observed in SF-1379 and the lowest in Luminox. Glucose content ranged from 6.89 to 17.34 mg g-1, with the highest value in Vega-F1 and the lowest in Luminox. The highest sucrose content was recorded in Caramelo (42.32 mg g-1), while the lowest was found in Calipos (7.9 mg g⁻¹). Total sugar content varied between 20.34 and 67.63 mg g-1, with the lowest in Calipos and the highest in SF-1379. In the main crop sowing period, the average fresh kernel yield, soluble solid content, and total sugar content of the cultivars were determined as 1864.87 kg da⁻¹, 1113.79 kg da-1, 13.95° Brix, and 48.95 mg g-1, respectively. In the second crop sowing period, these values were recorded as 2134 kg da-1, 1345.89 kg da-1, 16.18° Brix, and 47.99 mg g-1, respectively. According to the sowing time × cultivar interaction, the highest husk-free fresh ear yield, fresh kernel yield, soluble solid content, and total sugar content were recorded as follows: 2673 kg da-1 (second crop × SF-1280), 1687.33 kg da-1 (second crop × Sherbet F1), 21.25° Brix (second crop × Sherbet F1), and 70.74 mg g-1 (main crop × SF-1379). Conversely, the lowest values were recorded as follows: 1262 kg da-1 (main crop × Caramelo), 728.14 kg da⁻¹ (main crop × Caramelo), 11.83° Brix (main crop × Luminox), and 18.62 mg g⁻¹ (second crop × Calipos). The results of this study indicate that husk-free fresh ear yield and fresh kernel yield increased in the second crop sowing period. It is suggested that incorporating sweet corn cultivars into crop rotation and cultivating them as a second crop in regions with ecological conditions similar to Bilecik could help meet the demand for sweet corn and increase farmers' income. Furthermore, this study is expected to contribute to future breeding programs for sweet corn in the country.