Evaluation of the Effective Drought Stress Level for Drought Tolerance of Sugar Beet Genotypes

Water scarcity is a major limiting factor for agriculture in all arid and semi-arid regions of the world. Identification of various genotypes to produce drought-tolerant cultivars requires an assessment of their sugar yield under deficit irrigation conditions. Implementation of irrigation system and an appropriate level of water stress are therefore absolutely necessary in assessing genotypes for drought tolerance. For this purpose, four genotypes under eight irrigation treatments in a split plot design based on a Randomized Complete Block with four replications during the years 1387 and 1388 the Research and Education Center for Agriculture and Natural Resources Hamadan were evaluated. Eight irrigation treatments consisted of three treatments of furrow irrigation after 80, 130 and 180 mm, two treatments of tape irrigation, including irrigation after 30 mm with 100% and irrigation after 30 mm with 50% supply of water requirement of sugar beet and three tape irrigation treatments including 80, 130 and 180 mm cumulative evaporation from the evaporation pan in main plots and four genotypes in sub plots. The results showed that the interaction between genotypes and irrigation for the drought susceptibility index (DSI) was significant at 5% probability level. Reduced sugar yield of sugar beet genotypes caused by reduction of the amount of water (30mm tape irrigation with 50% of supply of water requirement) was more severe than the different irrigation intervals. Furrow irrigation is not an efficient and effective method of evaluating drought tolerance of sugar beet genotypes. Therefore, in order to evaluate drought tolerance of genotypes in breeding programs and produce drought-tolerant genotypes, tape irrigation method after 30 mm cumulative evaporation with supplying 50% of the plant water requirement, is introduced and recommended as an appropriate method and drought stress level.