Effect of Topping on Yield and Qualitative Characteristics of Autumn Sugar Beet (Beta vulgaris L.) Cultivars in Gorgan Condition

Leaves are one of the most important organs of plants where food (starch and sugar) are produced. These materials are used to maintain plant tissues, growth and production of new leaves. In order to evaluate the commercial fall growing cultivars of sugar beet, their potential to produce new leaves, a factorial experiment based on randomized complete block design was conducted with three replications at Varsan Agricultural Research Station (Gorgan), during 2018 growing season. The first factor consisted of 6 commercial sugar beet cultivars (5 foreign cultivars and Sharif, domestic) and the second factor of two times at toppings in May (middle stage of growth) and June (final stage of growth). Sugar beet root yield and some important quality characteristics were measured after harvesting. The results showed that the commercial cultivars showed significant differences in terms of yield and percentage of sugar (grade) at the one percent level of probability. Highest root yield was obtained from Jrakavas and lowest from veles cultivar. The highest percentage of sugar was due to veles and lowest to Rosagold cultivars. Topping reduced borb quantity and quality of sugar beet root, while May and June toppings reduced quality and yield of sugar beet root by 8.8% and 10.2% respectively as compared to the control treatment. The interaction effect of cultivar × topping was significant in all studied traits except root dry matter