Comprehensive study on in vitro propagation of some imported peach rootstocks b. In vitro rooting and acclimatization

Rooting is considered a critical stage in the micropropagation of Prunus sp. because it controls plant survival during acclimatization. Auxins and genotype are thought to play a significant role in root formation and induction. Therefore, the objective of the present work was to evaluate the effect of different indole-3-butyric acid (IBA) concentrations on the in vitro rooting and acclimatization of the Okinawa, Nemared, and Garnem peach rootstocks. Microcuttings of 2-3 cm in length were cultivated in MS medium supplemented with IBA (0.0, 0.5, 1.0, 2.0, 3.0, and 4.0 mg L^{- 1}) for the in vitro rooting stage. According to our results, the Garnem genotype exhibited the highest in vitro rooting rate, number of roots per plantlet, and root length. The level of 2.0 mg L^{- 1} of IBA was associated with rooting rates of 100%, 83.33%, and 75% for the Garnem, Okinawa, and Nemared, respectively. The Garnem genotype responded to 4.0 mg L^{- 1} of IBA with a fixed highest root number (12.33), which was the average number of roots per plantlet. Whereas, for the Nemared and Okinawa genotypes, the highest root number per plantlet was 8.00 and 5.00, respectively, in response to 3.0 mg L^{- 1} of IBA. The root lengths of the three genotypes varied significantly depending on the IBA treatment. The Garnem genotype presented the longest root length (5.33 cm), which was followed by the Okinawa genotype (2.49 cm), while the shortest value was presented with the Nemared (1.43 cm). The current study also demonstrated that the three genotypes developed abnormal roots and callus formation when the IBA concentration was increased to 4.00 mg L^{- 1}. Following acclimatization, the Garnem, Okinawa, and Nemared genotypes had respective average survival rates of 93%, 90%, and 75% for plantlets with fully grown shoots and roots.