Yield gap Analysis of Hybrid seed Production in Sugarbeet Fields: Ardabil Province of Iran

High-quality seeds with superior genetic potential are fundamental to achieving optimal performance in field crops. Hybrid seed production in sugarbeet is a complex, multi-stage process that begins with breeding parental lines and culminates in commercial hybrid seed production through crossing male-sterile single crosses with pollinators. In Iran, commercial sugarbeet hybrid seeds are produced almost exclusively in the Ardabil agricultural region. Given the substantial economic value of both basic and commercial sugarbeet seeds, this study aimed to identify yield-limiting factors in seed production fields. We collected 224 variables—including soil properties, field management practices, phenological characteristics, weather data, and seed yield—from 90 farms (98.8 hectares) during the 2022 growing season (March–September). Quantile regression analysis at τ = 0.9 identified five major yield-limiting factors: (1) number of days with relative humidity < 20% during the reproductive period, (2) number of days with relative humidity < 30% during vegetative growth, (3) field cover percentage, (4) sunshine duration during flowering, and (5) number of irrigations during vegetative growth. Collectively, these factors, identified during the 2022 production season, accounted for approximately 40% of the observed yield gap. Random forest analysis independently validated these five factors, with all ranking in the top 15 most important variables and collectively explaining 37.4% of model importance. Optimizing irrigation schedules during vegetative growth, combined with favorable humidity and sunshine conditions during flowering could substantially narrow the yield gap in sugarbeet seed production fields.