This study was conducted to determine the genotypic effect on regeneration induction in barley using 4 two — row and 4 six — row Japanese and Iranian barley selected from the cereal collection, Department of Agronomy, College of Agriculture, University of Tehran. Two weeks after pollination, immature embryos were dissected and planted in petri dishes using a solid MS medium with 2 mg/L of 2, 4-D. The petri dishes were incubated at 25±1 °C. The induced calli were sub — cultured on the same medium after about one month. In this study, the following variables were analyzed:
length of stem and root, regeneration rate, number of shoots in every callus, and size of immature embryo. Zarjo (a six — row genotype) showed the lowest of regeneration for all studying parameters and barley No. 17 (a two — row genotype) and Japanese barley No.1 (a six — row genotype) showed the highest regeneration rate. The analysis of variance indicated a significant effect of genotype on the variables, while there was a lower significant effect on plant within genotypes and lowest significant effect of spike per plant. The optimum size of immature embryo was between 0.5 and 1.6 mm, the best size being between 0.5 and 1.1 mm.