Estimation of combining abilities and heterosis of Septoria tritici blotch resistance in wheat genotypes.

Septoria tritici blotch (STB), caused by Mycosphaerella graminicola (anamorph S. tritici) is currently the most serious foliar disease of wheat worldwide. An eight-parent half diallel set of crosses between wheat genotypes were planted in the field of agricultural research center of Gorgan, Golestan in a randomized complete block design (RCBD) with three replicates. Plants were inoculated in tillering, long stem and appearance of flag leaf stages. Disease rating was visually recorded by using the double-digit scale (00-99). Disease severity and its AUDPC (sAUDPC) were calculated. The analysis of variance for combining ability showed the significant variation for both characters, indicating a wide range of variability among the genotypes. High significant variation due to general combining ability and also specific combining ability indicated the importance of additive as well as non additive types of gene action in inheritance of these characters; however Baker ratio showed the more importance of additive effects than non-additive effects of genes for both traits. Some negative and significant heterosis and heterobeltiosis effects were emphasized the existing of dominance gene effects to control resistance to STB.