Abstract

Abstract Influence of medium compositions on  different aspects of apple rootstocks growth was studied. The results showed that the different rootstock genotypes ‘M9’, ‘M27’ and ‘MM106’ had different potential of micropropagation. Multiplication rate was mainly dependent upon kind of plant  growth regulators (especially, 6-benzyl- aminopurine (BA) and genotypes). The best shoot production in terms of shoot number and shoot quality was obtained using 4.4 μM BA during the shoot multiplica- tion phase, and 8.8 μM BA and 2.8 μM GA3 during the shoot elongation phase for all genotypes (‘M9’, ‘M27’, ‘MM106’).  Application of high (2.8  μM) concentration of GA3 increased the elongation of adventitious shoots compared to low concentrations. The highest multiplication rate (5.7 shoots) and the highest amount of total fresh weight (2.25 g/jar), as growth rate, were produced by applying 4.4 μM BA for ‘M27’ genotype. Micropropagation potential of  ‘M27’ genotype was higher than other genotypes. ‘MM106’ genotype had the lowest multiplication rate (0.7 shoot/month) omitting BA. Multiplication of explants from the 1st  subculture was more sensitive to BA than that from the 3th  or 4th  subculture. The rooting of explants was promoted by IBA significantly and the best result for rooting was achieved in the half-strength MS medium containing 5.4 μM IBA. The highest percentage (40%) rooting was produced for ‘M27’ genotype. Root formation was increased with decreasing concentrations of BA (during shoot multiplication), but increasing auxins (IBA). Rooting percentage of shoot cultures in the low mineral concentration (1/2 MS medium) was significantly greater than shoot cultures in the high 2×MS medium.