Investigating agrotechnological features affecting sugar yield of Beta vulgaris L. in different planting dates for cultivar selection in northwest of Iran

In order to identify the agrotechnological features on sugar yield and determine the cause and effect relationships between them, 13 different domestic and foreign monogerm varieties of sugar beet were evaluated in a completely randomized design with four replications in terms of 11 important quantitative and qualitative traits in the station Miandoab Agricultural Research Station during three different harvest dates (October 15, October 30, and November 15) in the crop year 2017. The results of analysis of variance showed that the differences between the studied cultivars in terms of all evaluated traits were significant at p≤0.01. Phenotypic and genotypic diversity coefficients were high for most of the traits, which indicates relatively high diversity in the studied cultivars for the evaluated traits. The genetic correlation coefficients between the traits showed that the highest positive and significant correlation was between the sugar yield trait and the pure sugar yield traits (0.88), gross sugar percentage (0.71), and pure sugar percentage (0.65) in this order while there was a negative and significant correlation between the sugar yield trait and the traits of molasses sugar content (-0.62), alkalinity coefficient (-0.58), and root potassium content (-0.52). In the step-by-step multiple regression analysis, sugar percentage traits, gross sugar percentage, harmful nitrogen content and root yield were entered into the regression model in that order, which justified 84% of the total sugar yield. Based on the results of causality analysis, the traits of gross sugar percentage (1.12) and root yield (1.03) respectively had the most direct effect on sugar yield, so selection based on these traits can help us achieve the genotypes with high sugar yields.