Micropropagation protocol for the hybrid sorrel Rumex tianschanicus × Rumex patientia, an energy plant. Histological, SEM and flow cytometric analyses

Rumex tianschanicus x Rumex patientia is a prospective plant as a source of renewable energy and is also an important medicinal plant. In the present experiments an efficient and reproducible method for plant regeneration through the direct induction of shoot buds from hypocotyls was developed. The highest frequency of organogenetic response of explants was obtained on 7- and 12-day-old hypocotyls that had been cultured on the regeneration medium MS + 0.17 mg/l IAA + 2.2 mg/l BAP + 2% sucrose (44.06% and 48.88%, respectively). Successfully rooted plantlets were acclimated to in vivo conditions with more than a 90% survival rate. Histological analysis revealed direct organogenesis. Shoot buds arose from stele tissues and also from regenerated leaves (secondary organogenesis). Histological and SEM analyses showed a membranous-fibrillar structure, which was similar to the extracellular matrix (ECM), around non-morphogenic callus cells. The nuclear DNA content in leaves of plantlets regenerated in vitro, estimated using flow cytometry, was similar to donor plants (about 4.6 pg/2C). This is the first report concerning the micropropagation protocol for hybrid sorrel and the first DNA 2C-value estimation for this species.