General and Specific Combining Ability for Resistance to Bolting and Cercospora Leaf Spot, Technological Traits and Yield in Sugar Beet Lines Using Diallel Cross Analysis

To evaluate general and specific combining ability for resistance to bolting and Cercospora leaf spot, 36 hybrids derived from crosses between 9 sugar beet lines along with four checks were planted in Safiabad Agricultural Research Center (Dezful) in 2008-2009. The experimental design was a triple lattice design with three replications. Analysis of variance showed significant differences among genotypes for all of the traits with exception of sugar content, sodium, white sugar content and purity. Analysis of combining ability using Griffing's method II indicated that general combining ability of the lines was significant for all of the traits in probability level of 1%. Also, specific combining ability was significant for root yield, sugar yield, white sugar yield and potassium in probability level of 1% and for resistance to bolting and Cercospora leaf spot in probability level of 5%. In general, both additive and non-additive effects were effective in controlling the resistance to Cercospora and bolting, root yield, sugar yield and white sugar yield. However, resistance to bolting, root yield, sugar yield and white sugar yield were found to be mainly determined by the non-additive gene effects. The best parent for resistance to Cercospora and bolting was RR607, however, its root yield was not suitable. The best hybrid for resistance to Cercospora, root yield, sugar yield and white sugar yield was F1 of RR607×452. Furthermore, the best cross for resistance to bolting was SB-FIROZ×261. Nonetheless, cross of RR607×436 produced the best hybrid for resistance to bolting and Cercospora.