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Among the effective factors in sugar beet production, cultivar plays an important role. Rhizomania and rhizoctonia rot root are important challenges in spring sugar beet cultivation in Iran. About 40% of the sugar beet cultivation area is under the influence of these two diseases in Iran. Also, about 50% of the cultivation area is under the infection of rhizomania and nematode. Since the control of these soil-borne diseases is a difficult task, the use of resistant cultivars in infected fields is of special importance. Therefore, the use of dual resistance cultivar is the most efficient method of managing these diseases. To select a suitable cultivar, the field contamination, climatic condition, and quantitative and qualitative parameters of the cultivar should be considered. In all sugar beet growing countries, pilot trials comparing cultivars are conducted in the field. To compare both domestic and foreign sugar beet cultivars, the pilot trials were performed in the vicinity of sugar factories in Khoy, Piranshahr, and Naqadeh. Comparison of commercial sugar beet cultivars was performed in two separate trials on contaminated field. Two trials were performed in Khoybased on rhizomania-rhizoctonia (12 cultivars), and rhizomania-nematode (11 cultivars). However, only rhizomania-rhizoctonia (12 cultivars) trial was performed in Naghadeh and Piranshahr. In all trials, cultivars were randomly cultivatedin six rows with 30 m length without replication. Analysis of variance was performed using field data and laboratory results. Results showed significant difference among cultivars in three trials of rhizomania-rhizoctonia for all quantitative and qualitative traits. In rhizomania-rhizoctonia trial in three regions of Khoy, Naqadeh and Piranshahr, the mean root yield of Dena cultivar compared to Iranian cultivars Ekbatan and Sina were 60.87, 54.30 and 45.54 tons per hectare, respectively. Also, the mean root yield of Dena cultivar in three pilot experiments was superior to some foreign cultivars Anacond, Cadmus and Flores with yields of 56.05, 55.63 and 54.84 tons per hectare, respectively. Results showed significant difference among cultivars in one trial (rhizomania-nematode) for all quantitative and qualitative traits.The superiority of mean root yield of Kimia cultivar compared to Iranian cultivars Tara, Shokofa and Nika in Khoy pilot experiment was significant at 101, 71.52, 61.02 and 56.16 tons per hectare, respectively.
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