Evaluation and yield comparison of new sugar beet hybrids of rhizomania tolerance to deficit and optimum irrigation.

Rhizomania is known as the most destructive disease of sugar beet in the world. Most sugar beet soil born pathogens are developed by soil moisture and heat. One of the recommended ways to reduce disease damage in the infested areas is avoiding of excessive moisture which provides favorable conditions for disease development. It is essential to conduct experiments to evaluate the relationships between water consumption, sugar beet yield, and rhizomania damages. Therefore, this experiment was performed in an infested field at Zarghan station of Fars Research Center for Agriculture and natural Resources in 2009-2010. The research was conducted in the form of a split plot experimental design with the base of randomized complete block design with three replications. Main plots were sugar beet cultivars including cultivar 28064, 28058, 28928, Zarghan, Jam, and Rasool (control treatment). Subplots were applying three levels of irrigation regimes using line source sprinkler system. Irrigation regimes were set up based on the distance from the lateral tube and distance of four meters was considered for irrigation pipes. Data analysis was performed using SAS software and Duncan's multiple range tests was used to compare the treatment means. Results of annual and combined data analysis showed that hybrid 28928 had better performance compared to the other cultivars. Results of cultivar yield stability evaluation in different irrigation levels also indicated hybrids 28928 and 28064 had the higher yield in optimum and deficit condition compared to the cultivar average yield in different environments. Zarghan cultivar had the lower yield in deficit irrigation condition while, its yield was higher in normal irrigation condition. Regression analysis showed that the relation between White sugar content and water consumption was a polynomial faction so that sugar contact decreased in the range of 400-1000 millimeters irrigation while, sugar contact increased for treatments receiving irrigation water of less than 400 millimeters and more than 1000 millimeters. Since deficit irrigation decreased sugar beet yield, it could not be recommended in sugar beet production in spite of increasing sugar contact. Deficit irrigation apparently did not reduce disease damage but, Elyza test and OD (Optical Density) determination showed that deficit irrigation reduced OD and increased healthy roots. In this experiment, hybrids 28928, 28058 and Zarghan were proposed for the future study in this area.