In vitro Propagation of Two Sweet Cherry Rootstocks

Abstract

Sweet cherry production relies on conventional rootstock production to enhance tree vigor, improve precocity, and increase stress tolerance. However, conventional propagation methods (like cutting or grafting) of these rootstocks are slow, have low yield, and are not disease free. To address this gap, this research developed optimized in vitro propagation protocols for Gisela 6 and SL64 sweet cherry rootstocks using meristem culture techniques. The aim was to rapidly produce virus free, true-to-type plantlets by optimizing culture media and condition for each growth stage. SL64 and Gisela 6 explants were obtained and surface sterilized. Lateral and apical meristems (0.5mm) were excised and cultured in 12 media differing in basal media (MS, SH, DKW, and B5) and BAP concentration (0, 0,5, 1 mg/l). Proliferating shootlets were then subjected to six successive subcultures (multiplication phase) on the same range of media to assess the effects of mineral nutrients and plant growth regulators on shoot multiplication. Elongated shoots were then transferred in media containing different IBA concentrations (0, 0.5, 1 mg/l) and the four different basal media for rooting. Gisela 6 achieved up to 100% rooting with an average of 2.67 roots per plantlet on an MS medium supplemented with 1 mg/L IBA, developing a healthy root system. SL64 attained a maximum rooting percentage of about 72% on an SH medium with 1 mg/L IBA, with robust root growth (up to 3–4 roots per plantlet). Following rooting, plantlets were successfully acclimatized to external conditions in a controlled growth chamber, though survival rates differed between the two rootstocks. Gisela 6 had the highest number of reactive meristems and the highest number of regenerated shootlets in SH medium supplemented with 1mg/l BAP, whereas SL64 performed best MS medium with 0.5 mg/l BAP. Gisela 6 had the highest multiplication rate (15.42 shootlet per explant) and the highest shootlet length (3.58cm) in DKW media supplemented with 1mg/l, while SL64 had the highest multiplication rate in SH media with 1 mg/l BAP (7.63 shootlet per explant) and it recorded the longest shootlets in MS media with 0.5 and 1 mg/l BAP (~3.5 cm). Approximately 57.58% of SL64 plantlets survived the weaning period compared to only 16.67% of Gisela 6, indicating the need for improved hardening techniques for the more sensitive Gisela 6. These results emphasize the importance of developing genotype-specific acclimatization strategies to ensure consistent survival and reliable large-scale propagation of sweet cherry rootstocks.