Estimation of Gene Action and Genetic Parameters of Some Quantitative and Qualitative Characteristics of Sugar Beet (Beta Vulgaris L.) by Line × Tester Analysis

In crop breeding programs, comprehensive information is needed regarding the genetic structure of plant materials and their combinability. In this regard, the present study was carried out with the objectives of evaluating the general combining ability of parents and the specific combining ability of crosses, determining the nature and extent of gene action, and finally estimating the heritability of quantitative and qualitative traits of sugar beet hybrids by the analysis of line-tester crosses.

The study was conducted as a line-tester crossing using nine lines and two testers of sugar beet. For this purpose, maternal lines were planted in the middle lines and pollinator lines were cultivated in two lateral lines and all the crossings were done by observing the points related to isolation. A number of 18 hybrids obtained from the line-tester cross were cultivated and investigated in the agricultural research station of Shiraz in randomized complete block design with four replications during the crop season of 2019-2020.

The results of analysis of variance of root yield, sugar yield, white sugar yield, sugar content, white sugar content, sodium, potassium, harmful nitrogen, alkalinity coefficient, extraction coefficient of sugar and molasses sugar percentage showed that among studied hybrids, there is a significant difference at the 1% probability level in terms of all the traits except the two traits of sugar content and white sugar content. Line-tester analysis confirmed that the additive and non-additive effects of genes are involved in the expression and inheritance of root yield and sugar yield; However, in the genetic control of white sugar yield, sugar content, white sugar content, sodium, potassium, nitrogen, alkalinity coefficient, extraction coefficient of sugar and molasses sugar percentage, genes with non-additive effect have not played a role, and according to the significance of the general combining ability effect of the line or tester for the mentioned traits, only genes with additive effect are involved in the control. In total, from the used lines in the present study, 950123 and from the experimental testers, F-21121 had positive effects with regard to the improvement goals of sugar beet. S1-24 and F-21122 were associated with negative effects and caused a decrease in the breeding value of the traits.

Overall, obtained results showed the existence of diversity among hybrids derived from crossing between lines and testers. Based on the results, genes with both additive and non-additive effects are involved in the control of root yield and sugar yield, but in the inheritance of sugar yield, sodium, potassium, harmful nitrogen, alkalinity coefficient, extraction coefficient of sugar, and molasses sugar percentage, only genes with additive effect are involved. Considering that general combinability shows the additive effects of genes, so parents with high general combining ability also have a large additive effect that can be used in cultivar production.