AgNO3 improved micropropagation and stimulate in vitro flowering of rose (Rosa x hybrida) cv. Sena

Rose is one of the most important cut flower in the world. Rose micropropagation was used for production of clonal and disease-free plantlets and to breeding purposes. However, many important rose cultivars showed physiological disorders as early-leaf senescence and very low multiplication rate under in vitro conditions. Our hypothesis is that these symptoms were associated with high sensibility of these cultivars to ethylene accumulation on in vitro environment. The rose cv. Sena was in vitro cultivated under different concentrations of AgNO3 and two light sources, LED and fluorescent lamps, as a way to investigate in vitro similar symptoms to ethylene accumulation. AgNO3 at 1.0-2.0 mg L-1 solved the main in vitro physiological disorders observed in this rose cultivar. Also, AgNO3 stimulated induction of 50% of rose shoots to in vitro flowering at 2.0 mg L-1. Higher concentrations also resulted in flowering induction, but with imperfect flower development.

Phytochemical Composition, Antioxidant Capacity, and Enzyme Inhibitory Activity in Callus, Somaclonal Variant, and Normal Green Shoot Tissues of Catharanthus roseus (L) G. Don

This study aimed to investigate the impact of plant growth regulators, sucrose concentration, and the number of subcultures on axillary shoot multiplication, in vitro flowering, and somaclonal variation and to assess the phytochemical composition, antioxidant capacity, and enzyme inhibitory potential of in vitro-established callus, somaclonal variant, and normal green shoots of Catharanthus roseus. The highest shoot induction rate (95.8%) and highest number of shoots (23.6), with a mean length of 4.5 cm, were attained when the C. roseus nodal explants (0.6–1 cm in length) were cultivated in Murashige and Skoog (MS) medium with 2 µM thidiazuron, 1 µM 2-(1-naphthyl) acetic acid (NAA), and 4% sucrose. The in vitro flowering of C. roseus was affected by sucrose, and the number of subcultures had a significant effect on shoot multiplication and somaclonal variation. The highest levels of phenolics and flavonoids were found in normal green shoots, followed by those in somaclonal variant shoots and callus. The phytochemicals in C. roseus extracts were qualified using liquid chromatography–tandem mass spectrometry. A total of 39, 55, and 59 compounds were identified in the callus, somaclonal variant shoot, and normal green shoot tissues, respectively. The normal green shoot extracts exhibited the best free radical scavenging ability and reducing power activity. The strongest acetylcholinesterase inhibitory effects were found in the callus, with an IC50 of 0.65 mg/mL.

Rejuvenation of chicory and lettuce plants following phase change in tissue culture

Background A frequent problem associated with the tissue culture of Compositae species such as chicory (Cichorium intybus L.) and lettuce (Lactuca sativa L.) is the premature bolting to in vitro flowering of regenerated plants. Plants exhibiting such phase changes have poor survival and poor seed set upon transfer from tissue culture to greenhouse conditions. This can result in the loss of valuable plant lines following applications of cell and tissue culture for genetic manipulation. Results This study demonstrates that chicory and lettuce plants exhibiting stable in vitro flowering can be rejuvenated by a further cycle of adventitious shoot regeneration from cauline leaves. The resulting rejuvenated plants exhibit substantially improved performance following transfer to greenhouse conditions, with increased frequency of plant survival, a doubling of the frequency of plants that flowered, and substantially increased seed production. Conclusion As soon as in vitro flowering is observed in unique highly-valued chicory and lettuce lines, a further cycle of adventitious shoot regeneration from cauline leaves should be implemented to induce rejuvenation. This re-establishes a juvenile phase accompanied by in vitro rosette formation, resulting in substantially improved survival, flowering and seed set in a greenhouse, thereby ensuring the recovery of future generations from lines genetically manipulated in cell and tissue culture.