Chemical Components and Biological Activities of Essential Oils of Mentha × piperita L. from Field-Grown and Field-Acclimated after In Vitro Propagation Plants

In this work, we studied in vitro propagation of three cultivars of Mentha × piperita L. Murashige and Skoog medium (MS) supplemented with 0.5 mg·L−1 BAP was the most optimal medium for micropropagation of the cultivars studied. The ability of peppermint plants field-acclimated after in vitro micropropagation to produce essential oils (EOs) was investigated. EO was obtained by hydrodistillation from dried leaves and flowering shoots from control (field grown) plants and plants acclimated in field conditions after in vitro propagation. The samples were collected at the first and second year of vegetation, and their chemical composition was investigated using gas chromatography-mass spectrometry (GC-MS). Differences were observed in the yield, as well as in the quantitative and qualitative composition of the EOs extracted from the control plants and field-acclimated plants after in vitro propagation. Menthol was the main component of the EO in control plants, while pulegone and menthone were dominant in the EO pattern in field-acclimated in vitro regenerants in the first year of the growing season. However, in the second year of vegetation, the content of the main EO components in field-acclimated peppermint plants was approximately the same as in control plants. The antioxidant activity of EOs extracted from field-acclimated after in vitro micropropagation plants was found to be the same as in control field-grown M. × piperita plants.

Recent Advances of Biotechnological Tools on Diverse Species of Citrus: Current Applications and Future Prospects

Based on the long term conservation of several endangered and indigenous species of Citrus, significant impact of biotechnological tools particularly in terms of in-vitro micropropagation methods in addition to synthetic seed production using encapsulation of plant propagules including shoot tips, nodal segments, androgenic embryos, embryogenic callus, etc. in sodium alginate has been highlighted in this manuscript. When seed is not available in enough quantity for raising seedlings for rootstock or have low levels of polyembryony and do not produce adequate quantities of nucellar seedlings, then micropropagation techniques could quickly supply in vitro regenerated rootstock or budwood. Rapid, mass-production and cost-effective biotechnological tools for propagation of citrus rootstocks and budwood would be of great importance in this regard. Reports on another aspect of long term conservation particularly based on storage of cells, tissues and organs of drought tolerant species of Citrus at ultra-low temperature preferably at -196 ºC via applications of cryopreservation techniques using vitrification and encapsulation or dehydration methods has been highlighted in this manuscript. In addition, several research on techniques of in-vitro micrografting using superior scion and rootstocks of two different species of Citrus with an objective of eradication of virus infected citrus stocks for successful production of grafts have been reviewed. Furthermore, effects of explants either through direct and indirect regeneration and conversion into a complete disease free plantlet using suitable synthetic nutrient media along with plant growth regulators at various concentrations and combinations have been highlighted in this manuscript. Hence, the current review is primarily focused on the applications and its effects of superior biotechnological tools for long term conservation of diverse species of citrus for further increasing the potentiality of Citrus industries in addition to genetic improvement and genetic resource conservation.

Development of Micropropagation in Bigleaf Maple (Acer macrophyllum)

Natural populations of bigleaf maple (Acer macrophyllum Pursh) trees contain, at low frequency, individuals with stems that have attractive and valuable wavy grain in the wood. To maintain the genotype of these individuals, vegetative propagation is desired. To enable propagation from the limited amount of plant tissue that is often available, an in vitro micropropagation procedure was developed. A mix of wild trees was used as source material to generate a procedure that is genotype unspecific. Among tested basal media, DKW medium resulted in the highest frequency of growing shoots. For multiplication of shoots, removal of the apex of shoot explants was instrumental, presumably because this treatment broke a strong apical dominance in this species. Of tested hormone and hormone combinations, 0.1 μM thidiazuron produced the best results with an average of 3.2 axillary shoots per explant with an average of 3.7 nodes per axillary shoot after 1 month. Although rooting did not require hormone treatment, a 68% frequency of rooting was obtained on ½ MS supplemented with 1 μM IBA, 27% higher than hormone-free media. Taken together, we have developed a procedure for propagation of bigleaf maple from a limited amount of tissues that can be used to multiply various genotypes of interest.

Optimization of Modified Murashige and Skoog (MS) Medium Promoting Efficient Callus Induction in Zinnia elegans

Zinnia (Zinnia elegans Jacq.) occupies a pristine place in the garden for its bright colours and long flowering period. Zinnias are propagated by seeds hence genetic variation and a tendency for stock plants to decline in vigor over time is high. Young internodal explants of this species were grown on modified Murashige and Skoog (MS) medium supplemented with various growth hormones to evaluate callus induction. 2,4 dichlorophenoxyacetic acid (2,4-D) at 1.0 mg/L was shown to be the best choice for a high percentage of callus induction (70-73%) and a rapid growth rate of viable and healthy callus. A large-scale and quick callus generation protocol was developed in the lab and might be used for in-vitro micropropagation.

Impact of Encapsulation on Plantlet Regeneration from in vitro Grown Shoot tips of Citrus aurantifolia (Lime)

In order to conserve diverse species of citrus, an experiment on in vitro micropropagation and production of synthetic seeds from in vitro regenerated plant propagules of the species; Citrus aurantifolia (Lime) was carried out in which shoot tips were found to be suitable for excapsulation of artificial seeds. Highest rate of germination was obtained from the shoot tips when MS was supplemented with 1 mg/l BAP. Beaded shoot tips produced maximum germination (81.43%). Germinated synthetic seeds with well established roots and shoots were were taken out from the culture bottles and transferred in plastic cups containing a mixture of sterile soil: sand and farmyard manure at a ratio of 1:1:1. Seedlings were further shifted in earthen pots and kept in a partial shed net house for 7 days. Those seedlings were finally transferred under the field conditions for acclimatization. Plant Tissue Cult. & Biotech. 31(1): 43-49, 2021 (June)

In vitro Micropropagation of Pomegranate (Punica granatum L.) Derived from Cotyledon

A high frequency in vitro plant regeneration of pomegranate was established on MS medium supplemented with different concentrations and combinations of plant growth regulators. As explant cotyledons were employed for this study. Ninety percent of the cultured explants responded to form shoots from 30 days old in vitro raised seedlings after 90 days of culture initiation in MS containing 1.0 mg/l IBA + 0.1 mg/l NAA. The average number of shoots per explant was 10.0 ± 2.20, shoot length of 12.0 ± 2.40 cm, node per regenerated shoot was 9.0 ± 1.60 and the leaf number was14.0 ± 1.40. Well developed shoots were cultured on half strength of MS medium supplemented with 0.5 mg/l IBA, in which 90% shoot induced roots implanted after one month. The average number of root per shoot was 8.0 ± 0.90 and the average root length of 6.5 ± 0.40 cm was observed in this medium. Eighty percent plantlets were survived in the outdoor condition during the acclimatization period of seven days. Plant Tissue Cult. & Biotech. 31(1): 61-69, 2021 (June)