Estimation of gene action and genetic parameters of some characteristics related to sugar beet (Beta vulgaris L.) seed germination by line × tester analysis

Background and objectives: The seed vigor, which shows influence of parents on the life cycle and survival of plants, is also very important in for creating food security for human society. The most important objectives of the present study were to evaluate the general compatibility of parents and the specific combining of crosses, determining the nature and degree of gene action, and finally estimate the heritability of quantitative and qualitative traits of sugar beet hybrids through line-tester analysis.
Materials and Methods: Eleven pollinator lines of sugar beet were crossed with three male sterile single crosses using controlled pollination in the form of line-tester. A total of 33 obtained hybrids were investigated in terms of different traits related to seed germination in both laboratory and greenhouse conditions. The existence of diversity among the crosses was confirmed, and the calculation of the combining ability of the parents and their genetic effects was done by line-tester analysis.
Results: The results under laboratory conditions showed that there is a significant difference between the crosses in terms of of different germination traits, non-germinated filled cluster, empty cluster and 1000 seed weight. The line had a significant effect on the characteristics of germination capacity, germination uniformity, empty cluster and 1000 seed weight. Tester mean square for germination rate, mean germination time, empty cluster and 1000 seed weight showed a significant difference. Line-tester interaction resulted in a significant difference for the mean germination time, empty cluster and 1000 seed weight. The results of analysis of variance of different traits in greenhouse conditions indicated significant differences between the crosses in terms of the traits of seedling emergence and mean shoot dry weight of a single seedling. The effect of line was significant only on the seedling emergence capacity. The tester factor had a significant effect on all studied traits. Line-tester interaction was significant only for seedling emergence capacity. The general combinability of lines 970023 and 970100 for germination capacity, lines 970038 and 970100 and all three experimental testers for germination rate and 970097 for germination uniformity was significant in positive direction. Line 970097 and tester 474*7112-36-6 decreased the mean germination time and Lines 970038, 970023, 970014, 970100 and tester MS KWS and 7112*SB36 caused a decrease in empty cluster. Testers MS KWS and 7112*SB36 caused the reduction of empty cluster with their negative effect. Regarding the 1000 seed weight, lines 970094, 970014 and 970031 and testers 7112*SB36 and MS KWS had positive and significant general combining ability. In the greenhouse experiment, in relation to the seedling emergence capacity, lines 970100, 970023 and 970038 and MS KWS tester and for seedling emergence rate, lines 970038, 970100 and three testers showed positive and significant general combining ability. For the mean shoot dry weight, line 970098 and tester 7112-36-6*474 had positive significant general combining ability, but tester SB36*7112 caused a decrease in mean shoot dry weight.
Conclusion: Considering that general combining ability shows the additive effects of genes, therefore, parents with high general combining ability also have a high additive effect that can be used in the production of synthetic cultivars. On the other hand, these parents can be used through recurrent selection in the development of inbred lines and also as testers to evaluate new inbred lines. According to the obtained results, the selection of useful compounds for the production of suitable hybrids is determined by the breeding goals. Therefore, by considering the positive or negative specific combining ability value of parental compounds for a trait, it is possible to increase genes with non-additive effect to produce hybrids.