The benefits of increased hybrid vigor, which often occur crossing unrelated plants or animals, have been recognized for centuries. In this study, hexaploid oat genotypes E44, K1, and A52 belong to A. sativa and A45 belonging to A. byzantina species were crossed. Heterosis, heterobeltiosis and standard heterosis values were calculated for 11 traits on 12 hybrids belong to K1 x E44 cross (ten hybrids), K1 x A45 cross (one hybrid) and K1 x A52 cross (one hybrid) with the parents. According to the results, parents varied for all traits while hybrids were varied for flag leaf length (FLL), tiller number (TN), 1000-grain weight (1000-GW), grain number per panicle (GNP), grain weight per panicle (GWP), single plant grain yield (SPGY) and biomass (B). K1 x A52 cross had the highest plant height (PH, 201.0 cm), TN (22) and 1000-GW (47.1 g). On the other hand, the highest stem diameter (SD, 9.0 mm), flag leaf width (FLW, 4.0 cm), panicle length (PL, 53.0 cm), GNP(98.0) and GWP (3.2 g) were obtained from K1 x A45 cross. However, K1 x E44 cross had the highest FLL (42.7 cm), SPGY (42.6 g) and B (108.7 g) values. Heterosis values of the oat crosses were significant for all traits except stem diameter, flag leaf length and panicle length, while stem diameter and panicle length for heterobeltiosis and plant height and stem diameter for standard heterosis. Heterosis values were ranked between -26.8 and 282.3% while heterobeltiosis values were between -45.6 and 248.0%, and standard heterosis values were between -2.7 and 419.0%. The highest heterosis and standard heterosis values (282.3 and 419.0%, respectively) were determined for SPGY in K1 x E44 population, while the highest heterobeltiosis value (248.0%) was determined for biomass in K1 x A52 population.
