One of the most important factors influencing the economic income of grape producers is the cultivar type, the timing of market entry, and the growing environment. Low income among vineyard owners is often attributed to factors such as improper grape cultivars, unsuitable market prices at harvest, water shortages, inappropriate training systems, and high sensitivity of shoots and fruits to fungal diseases. Grapes grown in open fields with trailing systems frequently suffer greater damage from spring frost and fruit rot caused by late summer rains, compared to other training methods. To enable off-season grape production and increase growers’ income in North Khorasan province, a study was conducted during the 2019–2023 cropping seasons. Four grape cultivars—Yaghouti, Kandori, Flame Seedless, and Khalili Siah—were evaluated using a bilateral cordon trellis system in multi-span greenhouses with 5-year-old vines. Results showed that greenhouse cultivation significantly improved grape yield and price compared to open-field conditions. All cultivars grown in greenhouses exhibited increased yield and market price, as well as reduced fruit rot and higher sugar content. The highest fruit yield was recorded for the Flame Seedless cultivar at 65,702 kg/ha, while the lowest was for Khalili Siah at 38,403 kg/ha—an increase of 27,292 kg/ha (71% higher yield). Despite its lower yield, Khalili Siah had the highest economic return due to its early ripening (by one month), resistance to fungal diseases, and higher market price (120,000 IRR per kg) compared to the other cultivars.
)
)