Evaluation of sugar beet S1 pollinator lines using drought tolerance indices

Plants are encountered with biological and non-biological stress at different stages of their development. Drought stress is a serious threat to producing successful crops around the world, including Iran. One of the ways to select drought tolerant cultivars is to evaluate and determine their compatibility in two stressed and non-stressed environments. And also with using selectable indices, tolerant genotypes can be selected. The aim of this study was to evaluate of sugar beet S1 pollinator lines under non-stress and drought stress conditions in order to select promising and drought tolerant lines.

This experiment was conducted to evaluate the drought tolerance indices of 30 sugar beet genotypes (29 S1 pollinator lines with origin population) and their relationship with sugar yield in Khorasan Razavi Agricultural and Natural Resources Research and Education Center in two separate experiments under field conditions with randomized complete block design with three 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 drought stress conditions, respectively. Yield Stability Index (YSI), Stress Tolerance (TOL), Mean Productivity (MP), Geometric Mean Productivity (GMP), Stress Susceptibility Index (SSI), Stress Tolerance Index (STI), Drought Tolerance Index (DTI), Beet Tolerance Index (BTI), Harmonic Mean Index (HARM), Yield Index (YI), Reduction Yield Index (YR) , Drought Index (DI) indices were used to evaluate susceptibility and tolerance of the genotypes. To study the variables simultaneously, the relationship between the indices and the identification of tolerant genotypes was performed by the principal component analysis and the plot of the plot was plotted based on the first two components. Analysis of variance and estimation of correlations were performed with SAS 9.1 software and also analysis of the main components and plotting the biplot charts were done using Minitab 18.1 software.

Combined analysis of variance showed that there was a significant difference (p≤0.01) among studied genotypes and different irrigation regimes for sugar yield. The highest yield of sugar in non-stress and drought stress conditions were observed in S1-45 (8.98 ton / ha) and S1-3 (5.15 ton / ha), respectively. S1-80, S1-95, S1-45, S1-3, S1-13, S1-8 lines and origin population had sugar yield above average under both conditions of irrigation and they were in group A (high yield under non-stress and stress conditions) based on Fernandez' instructions. The study of correlation coefficients between sugar yield and tolerance indices in non-stress and drought stress conditions indicated the superiority of MP, GMP, STI, BTI and HARM indices.

In general, the results showed that S1-3, S1-45 and S1-80 lines, both in terms of MP, GMP, STI, and sugar yield indicators under stress conditions, they can be identified as the most susceptible genotypes to drought stress.