Introduction
Autumn cultivation has been proposed as a strategy to take advantage of seasonal rainfall and reduce irrigation water consumption. However, this approach has faced major challenges, particularly the incidence of Cercospora leaf spot disease and bolting, across different regions.
 Materials and Methods
Considering the adverse effects of bolting and Cercospora leaf spot disease on both the quantitative and qualitative yield of autumn-sown sugar beet, this study was conducted to evaluate the performance of 16 sugar beet cultivars in terms of bolting resistance, Cercospora resistance, and yield potential. The experiment was carried out during the 2022–2023 growing season using a randomized complete block design with four replications in two regions: Khuzestan province (Dezful) and Golestan province (Gonbad-e Kavus). In the Dezful region, the bolting percentage was zero for all cultivars; therefore, this trait was excluded from the analysis of variance for that location.
 Results and Discussion
In Dezful region, analysis of variance indicated significant differences among cultivars for all measured traits, except bolting and sugar content. Mean comparisons showed that the highest white sugar yield was obtained from the Vanilla (10.60 t ha⁻¹) and Volga (9.49 t ha⁻¹) cultivars. The highest root yield was recorded for Vanilla (83.10 t ha⁻¹) and Sibelius (79.81 t ha⁻¹). The highest white sugar content was observed in Volga (13.77%), Flixter (13.36%), and Algar (13.26%). Regarding root impurities, Volga (1.83 meq 100 g⁻¹ pulp) and Balzan (1.89 meq 100 g⁻¹ pulp) had the lowest sodium content, while Volga (2.55 meq 100 g⁻¹ pulp) and Allegra (2.56 meq 100 g⁻¹ pulp) had the lowest potassium levels.The lowest amino nitrogen content was found in Allegra (2.94 meq 100 g⁻¹ pulp), Algar (3.43), Pegaz (3.35), and Contenta (3.09). Sugar extraction efficiency was highest in Volga (86.46%), followed by Balzan (83.36%) and Lodata (83.33%). Among the evaluated cultivars, only Casablanca exhibited a semi-resistant reaction to Cercospora leaf spot (score 3.88 out of 9), while the remaining cultivars ranged from semi-sensitive to sensitive (scores >4). No bolting was observed in any cultivar in Dezful, whereas the sensitive control exhibited 36.84% bolting. This suggests that although conditions were partially favorable for bolting, the tested cultivars expressed resistance, likely influenced by climatic conditions during the growing season.
In the Gonbad-e Kavus region, analysis of variance showed that cultivar effects were significant for all traits except root yield and sodium content. Mean comparisons showed that the highest white sugar yield was obtained from Volga (10.26 t ha⁻¹) and Algar (9.21 t ha⁻¹). The highest sugar content was recorded in Volga (17.33%), Contenta (17.28%), Sy_muse (17.24%), Vanilla (17.13%), and Flickster (17.11%). The highest white sugar content was observed in Volga (14.87%), Sy_muse (14.27%), Vanilla (13.96%), and Contenta (13.94%). Regarding root impurities, Volga (4.73 meq 100 g⁻¹ pulp) had the lowest potassium content, while other cultivars showed higher potassium levels (>5 meq 100 g⁻¹ pulp). Except for Oxalide (2.03 meq 100 g⁻¹ pulp), Laudata (1.72), and Balzan (1.77), which showed relatively high amino nitrogen levels, the remaining cultivars had low amino nitrogen content (<1.5 meq 100 g⁻¹ pulp). The highest sugar extraction efficiency was observed in Volga (85.56%). Most cultivars showed resistance to semi-resistance against Cercospora leaf spot, with Balzan and Vanilla showing complete resistance. The lowest bolting percentages were observed in Balzan (3.32%), Oxalide (3.62%), Sibelius (3.96%), and Cardamone (4.14%), whereas the sensitive control showed a bolting rate of 93.41%.
Conclusion
Overall, the environmental conditions of Dezful were more favorable for the development and establishment of Cercospora leaf spot disease than those of Gonbad-e Kavus. In contrast, environmental conditions in the Gonbad-e Kavus region were more conducive to bolting than in Dezful. These findings indicate that successful autumn cultivation of sugar beet depends not only on selecting cultivars resistant to bolting and Cercospora leaf spot but also on careful consideration of regional environmental conditions.