Studies on the tissue culture of apple have allowed for molecular, biotechnological and applied breeding research to advance. In the past 8 years, over 100 papers advancing basic biology, genetic transformation and cryobiology have emerged.

In general, in vitro virus elimination is based on the culture of isolated meristem, and in addition thermotherapy, chemotherapy, electrotherapy, and cryotherapy can also be applied. During these processes, plantlets suffer several stresses, which can result in low rate of survival, inhibited growth, incomplete development, or abnormal morphology. Even though the in vitro cultures survive the treatment, further development can be inhibited; thus, regeneration capacity of treated in vitro shoots or explants play also an important role in successful virus elimination. Sensitivity of genotypes to treatments is very different, and the rate of destruction largely depends on the physiological condition of plants as well. Exposure time of treatments affects the rate of damage in almost every therapy. Other factors such as temperature, illumination (thermotherapy), type and concentration of applied chemicals (chemo- and cryotherapy), and electric current intensity (electrotherapy) also may have a great impact on the rate of damage. However, there are several ways to decrease the harmful effect of treatments. This review summarizes the harmful effects of virus elimination treatments applied on tissue cultures reported in the literature. The aim of this review is to expound the solutions that can be used to mitigate phytotoxic and other adverse effects in practice.

In vitro experiments were conducted to study the responses of potato (Solanum tuberosum L.) genotypes to osmotic stress. In vitro shoot cultures of 27 breeding lines and their drought-tolerant parents (referent lines: C103 and C107) were tested under osmotic stress induced by addition of PEG 6000 (Mw = 6000; 5.0, 7.5, 10.0%, w/v), D-mannitol (0.1, 0.2, 0.3 M) and PEG 600 (Mw = 600; 2.5, 5.0, 7.5%, w/v) to the Murashige-Skoog medium. Stress index (SI) was calculated from shoot length (SL) and root length (RL), root numbers (RN) and the rate of surviving shoots (SR) (SI_SL;RL;RN;SR = Parameter_SL;RL;RN;SR of treated shoots/Parameter_SL;RL;RN;SR of control shoots × 100) to compare genotypes. In the average of each breeding line and concentration, the osmotic agents resulted in SI values of 40.1, 60.8, 82.6 and 76.0 for SI_SL, SI_RL, SI_RN and SI_SR, respectively. In general, all SI values of C103 and SI_RL,RN of C107 were significantly higher than those of the breeding lines. Nine breeding lines were found to be promising based on their final ranking. According to the results, 7.5% and 10% PEG 6000 or 0.2 M and 0.3 M D-mannitol treatments proved to be suitable for the selection of osmotic stress-tolerant genotypes.

Harsh climates, i.e., drought, extreme temperatures, and toxic gases, pose issues to agriculture by altering plants’ growth and yield. Biotechnology with biochemical defense approaches is beneficial for generating new plants/varieties with extra resilience to adverse conditions. In response to stress, cultures show an enriched level of secondary metabolite synthesis. Here, an efficient in vitro propagation method using axillary shoot proliferation, along with callus formation, was established in Glycyrrhiza glabra L. The phytochemical composition of in vitro and in vivo grown tissues was analyzed using a gas chromatography–mass spectrometry (GC–MS) technique, and the biochemical attributes were measured and compared in different investigated tissues. Callus formation from root explants was achieved with a frequency of 88.89% on MS medium containing 2.0 mg/L BAP and 0.5 mg/L 2,4-D. Axillary shoot proliferation was obtained from dormant buds when cultured onto MS supplemented with BAP alone, or in combination with, IAA. The maximum shoot proliferation (94.44%) was recorded on MS with 1.0 mg/L BAP with an average shoot length of 10.5 cm. The regenerated shoots were subcultured and transferred to the root induction medium, supplemented with various concentrations of IAA/IBA, wherein 2.0 mg/L IBA resulted in the best rooting frequency (88.89%). The GC–MS-based phytocompounds analysis of the methanolic extracts of root-derived callus and in vivo- and in vitro- grown root tissues was conducted. These samples revealed the presence of more than 35 therapeutically important bioactive compounds, such as methylglabridin, sitosterol, lupeol, squalene, stearic acid, linoleic acid, etc. The biochemical parameters, like total phenolic content, flavonoid content, DPPH scavenging activity, superoxide dismutase, and peroxidase activity were also measured. All the biochemical attributes were found to be higher in in vitro derived roots than the callus and in vivo grown root (donor) samples. These findings demonstrated that callus (root derived) and in vitro roots are a stable and potent source of multiple phytocompounds, encompassing medical significance with wide applications. This study may serve as an alternative opportunity in the sustained and continuous synthesis of important compounds without harming natural vegetation and normal environment.

An effective and reproducible micropropagation protocol was developed for Centratherum punctatum Cass. Successful in vitro initiation of callus and subsequent plant regeneration were obtained on nodal explants cultured on MS medium supplemented with plant growth regulators (PGRs). The maximum frequency of callus formation (98.3%) was noted on MS containing 4.0 mg/L 6-Benzylaminopurine (BAP) and 3.5 mg/L Kinetin with a maximum callus weight of 2.02 g. The best shoot induction frequency (100%) with an average of 30.2 shoots per explant was achieved when 4.5 mg/L BAP and 4.0 mg/L Kinetin were added to the MS. The same PGR combination resulted in the best callus-mediated shoot formation (8.3 shoots/callus mass). The highest rhizogenic response (95.3%) with an average 26.1 roots per shoot and root length of 6.2 cm was obtained with 1.0 mg/L Indole-3-acetic acid (IAA)-supplemented MS medium. The gas chromatography–mass spectrometry (GC-MS) technique was applied in the present study to analyze the methanolic extracts of the leaf, callus, and root of regenerated C. punctatum shoots to detect the different phytochemical constituents. The leaf extract of the regenerated C. punctatum showed 37 phytocompounds; some important bioactive compounds were the Phytol,1,6-Octadien 3,5-Dimethyl-Cis, 4,8-Dimethylnona-3,8-dien-2-one, 2,6-Octadiene, Stigmasterol, Chondrillasterol, Lanosteryl acetate, etc. In the callus, the extract had a total of 57 phytocompounds; among them, the Stigmasterol, Guanosine, and Tri-decanoic acid were the major ones. In the root extract, the GC-MS revealed a low number of 23 phytocompounds, the important compounds of which were Stigmasterol, Trimethylsilyl (TMS) derivative, Chrysantenyl 2-methuylbutanoate, 4-tert-Butoxybutan-1-ol, etc. The order in terms of numbers of phytocompounds present in tissue sources are callus > leaf > root.