Evaluation of resistance of sugar beet commercial varieties to rhizomania and rhizoctonia root rot diseases

Rhizomania is one of the most destructive diseases of sugar beet which leads to severe losses in root yield and sugar content. Rhizoctonia root rot is another important disease prevailent in most beet production areas of Iran. These soilborne diseases could be effectively controlled by using disease resistant varieties. In this research, some foreign and domestic commercial sugar beet varieties were investigated in 2009. Four rhizomania experiments were carried out in randomized complete block design with 4 replicates in two naturally infected locations (Mahsad and Shiraz) and one rhizoctonia experiment was conducted in three naturally infected locations (Mahsad, Kerman and Uromie). In each experiment, yield and quality characteristics were measured in addition to disease resistance assessement. In the rhizomania experiments of Mashad, six varieties (F-20727, F-20706, F-20703, F-20704, F-20705 and F-20739) produced the highest white sugar yield compared with the mean of disiease resistant checks. They were also superior in quality characters. The disease scores of these varieties (assessed on a 1-9 scale) were less than 5 indicating that they could be classified as resistant varieties. In the rhizomania experiments of Shiraz, 9 varieties (F-20727, F-20722, F-20734, F-20668, SR87, F-20655, F-20726, F-20712, F-20707, F-20698) produced the highest 59 white sugar yield compared with the mean of disiease resistant checks. The disease scores of these varieties were less than 2.5 indicating that they could be classified as resistant varieties. In total, in the four experiments of Shiraz and iMashad, the cultivar F-20727 was superior to other cultivars. In the rhizoctonia experiment of Kerman, 9 varieties (F-20680, F-20695, F-20719, F-20669, F-20733, F-20722, F-20675, F-20714, F-20693) produced the highest white sugar yield compared with the mean of disiease resistant checks. They were also superior in quality characters. In the rhizoctonia experiments of Mashad and Uromei, the cultivars F-20714 ans F-20698 respectively were found to be better than the resistant checks with respect to white sugar yield and quality characters. In conclusion, F-20727 and F-20714 could be recommended for rhizomania and rhizoctonia infected areas, respectively.