Evaluation of quantitative and qualitative characteristics of sugar beet cultivars in spring and autumn cultivation under conditions of rhizomania infection

Autumn cultivation of sugar beet is one of the strategies for increasing sugar beet production with minimum amount of water consumed due to the use of autumn and winter precipitation and avoiding the need for irrigation in very dry summer air. Rhizomania is recognized as the most destructive disease of sugar beet in the world. The aim of this study was to investigate the quantitative and qualitative characteristics and the effect of rhizomania viral disease on susceptible and tolerant cultivars of sugar beet in spring and autumn cultivation in polluted soil conditions of Torbat-e Jam region.

In this research, five domestic and foreign commercial cultivars including rhizomania-resistant and susceptible commercial cultivars were cultivated in spring and autumn in a field infected with rhizomania disease of Torbat-e Jam Sugar Factory. The experiment was conducted as split plot in a randomized complete block design with four replications in 2017-18 growing season as sowing time as main factor in two levels (spring and autumn) and cultivar as sub factor was considered at five levels (Giada, Dorothea, SBSI002, Monatunno and Rasoul). The traits studied in this study included root yield, sugar content, sugar yield, white sugar content, white sugar yield, sodium, potassium, trace nitrogen, sugar extraction coefficient, molasses sugar, disease severity and ELISA test index (OD). Analysis of variance was performed using SAS v.9.1 statistical software. Mean comparisons of traits were performed using LSD test at the probability level of 5 and 1%.

Analysis of variance showed that there was a significant difference between the two spring and autumn sowing times in terms of quantitative and qualitative yield and rhizomania damage. Also, for all studied traits, except for potassium and nitric oxide, there was a significant difference at 1% probability level between different sugar beet cultivars. The highest values were observed for root yield, sugar yield, white sugar yield and potassium, and the lowest values for severity of disease and ELISA index in Giada cultivar and autumn cultivation conditions. Whereas, Rasoul cultivar had the lowest values for sugar content, sugar yield, white sugar yield, potassium and nitrogen in spring cultivar and the highest values for disease severity and ELISA.

In general, the results showed that autumn sowing leads to improved quantitative and qualitative yield and reduced rhizomania damage in sugar beet. According to the results of this study, autumn cultivation of Giada is suitable in Torbat-e Jam region