Evaluation of drought tolerance in sugar beet test cross hybrids under water deficit stress

Introduction Plants encounter biological and non-biological stress at different stages of their development. In this regard, drought stress is the most important non-seismic factor that, with global warming and the increased likelihood of drought, it is anticipated that by 2050, the performance of agricultural products in 50 percent of the world's agricultural land would be at serious risk. This will lead to a significant reduction in the production of food products. The dry and semi-arid climate of the country has become inevitable the cultivation and production of crops under the conditions of environmental stresses (drought, salinity and heat).Crops are show different reactions against these stresses. The occurrence of any of the stresses, or a combination of them, leads to a reduction in production. Sugar beet is one of the plants that tolerates these stresses. The aim of this research was to evaluate the tolerance of sugar beet test cross hybrids under non-stress and water deficit stress conditions in Khorasan Razavi province in order to select promising and drought tolerant hybrids. Materials and methods This experiment was conducted to evaluate the drought tolerance of sugar beet test cross hybrids (57 hybrids) with seven controls including IR7, Mandarin, Jolgeh, Paya, Fotora, SC (7112*SB36) and origin population) in Khorasan Razavi Agricultural and Natural Resources Research and Education Center in two separate experiments under field conditions with unbalanced lattice design (8*8) with four replications in 2016. Irrigation was done routinely up to the thinning. Subsequent irrigations were done after 90 mm and 200 mm evaporation from the class A evaporation pan in non-stress and water deficit stress conditions, respectively. In this research, traits such as root yield, sugar content, sugar yield, Na, K, N, alkalinity, molasses sugar, white sugar content, white sugar yield and extraction coefficient of sugar were measured. Analysis of variance, estimation of correlations and step wise regression were performed with SAS 9.1 software and also path analysis was done using Amos v19 software. Results and discussion Combined analysis of variance showed that there was a significant difference (p≤0.01) among studied genotypes and different irrigation regimes for all traits. The highest white sugar yield in non-stress and water deficit stress conditions were observed in (7112 * SB36) * S1 – 73 (13.34 ton / ha) and Mandarin (9.37 ton / ha), respectively. Correlation analysis revealed that the relationship between white sugar yield with root yield, sugar content, sugar yield, white sugar content and extraction coefficient of sugar was significantly positive in two conditions, while its correlation with Na, K, alkalinity and molasses sugar was significantly negative. According to the results of the stepwise regression analysis, more than 99 percent of white sugar yield variation was explained by sugar yield, extraction coefficient of sugar, root yield and sugar content in non-stress and drought stress conditions. Conclusions In general, the results showed that the genotypes 61 (Mandarin), 60 (IR7), 63 (Fotora), 51 (7112 * SB36) * S1 – 73), 40 (7112 * SB36) * S1 - 66) and 56 (7112 * SB36) * S1 - 72), which were superior in terms of stress tolerance index (STI) and also in terms of yield traits in stress condition, were introduced as the most drought tolerant genotypes.