Plant tissue culture techniques have become an integral part of progress in plant science research due to the opportunity offered for close study of detailed plant development with applications in food production through crop improvement, secondary metabolites production and conservation of species. Because the techniques involve growing plants under controlled conditions different from their natural outdoor environment, the plants need adjustments in physiology, anatomy and metabolism for successful in vitro propagation. Therefore, the protocol has to be optimized for a given species or genotype due to the variability in physiological and growth requirement. Developing the protocol is hampered by several physiological and developmental aberrations in the anatomy and physiology of the plantlets, attributed to in vitro culture conditions of high humidity, low light levels and hetero- or mixotrophic conditions. Some of the culture-induced anomalies become genetic, and the phenotype is inherited by clonal progenies while others are temporary and can be corrected at a later stage of protocol development through changes in anatomy, physiology and metabolism. The success of protocols relies on the transfer of plantlets to field conditions which has been achieved with many species through stages of acclimatization, while with others it remains a challenging task. This review discusses various adjustments in nutrition, physiology and anatomy of micro-propagated plants and field grown ones, as well as anomalies induced by the in vitro culture conditions.

Rye is an important crop widely cultivated in Europe, but one of the hardest to improve due to its allogamy and self-incompatibility. The market for rye-based products is constantly growing thanks to the popularity of organic farming, feed production and diverse industry applications. To address these demands, new highly productive hybrid rye varieties are needed. Currently, full potential of heterosis in rye breeding is hard to reach due to the limited success in in vitro cultures. This review summarizes the progress in rye in vitro cultures and proposes novel approaches to overcome recalcitrance in this species.