Evaluation of yield and resistance of sugar beet cultivars to fungal root rots under drought stress

There have been many reports of the high incidence of sugar beet root rot fungi following the drought stress periods in Iran. This study was conducted to evaluate the yield and resistance of sugar beet commercial cultivars to the fungal root rots after drought stress. Thirty cultivars were planted in randomized complete block design in two different fields over two consecutive years (2018–2019). In order to apply drought stress, an irrigation system was designed based on the evaporation of 180 mm water from the class (A) pan and compared with the stress-free plots. The area under the disease progress curve (AUDPC) was calculated based on the rate of plant loss progress in three monitoring dates after drought stress. Also, the final white sugar yield (WSY ha−1) was calculated after harvest. The results of AUDPC and WSY ha−1 (Year × Field) were obtained for each cultivar. Plant losses in drought stress plots were 23.05% more than stress-free plots. The high resistance to root rot (100   10). A significant relationship was observed between WSY ha−1 rates and resistant cultivars under drought stress and stress-free plots. The study confirmed the effect of drought stress on the predisposition of sugar beet commercial cultivars to fungal root rots. As a result, the most resistant and high-performance cultivars were identified under drought conditions for greater productivity.