Plant tissue culture has become one of the fundamental tools of plant science research. It is extensively employed in the production, conservation and improvement of plant resources. The presence of somaclonal variation in populations derived from tissue culture is affecting the use of tissue culture negatively and has remained a major problem. Conversely, it is a source of new desirable clones/variants with better agronomic traits. In this review, we summarize the possible causes, detection methods and desirability of variants. Somaclonal variation is one of the most researched and reviewed topics. Hence, we restricted ourselves to outlining various examples which may be used as important references for researchers who intend to identify and/or characterize somaclonal variants while using tissue culture for research and production. Emphasis is placed on the negative effects of somaclonal variation. However, this review also includes examples of some useful variants generated as a result of somaclonal variation.

Somaclonal variation in plants: causes and detection methods

In vitro techniques have found increasing use in the conservation of threatened plants in recent years and this trend is likely to continue as more species face risk of extinction. The Micropropagation Unit at Royal Botanic Gardens, Kew, UK (RBG Kew) has an extensive collection of in vitro plants including many threatened species from throughout the world. The long history of the unit and the range of plants cultured have enabled considerable expertise to be amassed in identifying the problems and developing experimental strategies for propagation and conservation of threatened plants. While a large body of knowledge is available on the in vitro culture of plants, there are limited publications relating to threatened plant conservation. This review highlights the progress in in vitro culture and conservation of threatened plants in the past decade (1995–2005) and suggests future research directions. Works on non-threatened plants are also included wherever methods have applications in rare plant conservation. Recalcitrant plant materials collected from the wild or ex situ collections are difficult to grow in culture. Different methods of sterilization and other treatments to establish clean material for culture initiation are reviewed. Application of different culture methods for multiplication, and use of unconventional materials for rooting and transplantation are reviewed. As the available plant material for culture initiation is scarce and in many cases associated with inherent problems such as low viability and endogenous contamination, reliable protocols on multiplication, rooting, and storage methods are very important. In this context, photoautotrophic micropropagation has the potential for development as a routine method for the in vitro conservation of endangered plants. Long-term storage of material in culture is challenging and the potential applications of cryopreservation are significant in this area. Future conservation biotechnology research and its applications must be aimed at conserving highly threatened, mainly endemic, plants from conservation hotspots.

https://bioone.org/journals/In-Vitro-Cellular-and-Developmental-Biology---Plant/volume-42/issue-3/IVP2006769/CONSERVATION-iIN-VITRO-i-OF-THREATENED-PLANTS--PROGRESS-IN/10.1079/IVP2006769.pdf

Conservation in vitro of threatened plants - progress in the past decade

The advancements made in tissue culture techniques has made it possible to regenerate various horticultural species in vitro as micropropagation protocols for commercial scale multiplication are available for a wide range of crops. Clonal propagation and preservation of elite genotypes, selected for their superior characteristics, require high degree of genetic uniformity amongst the regenerated plants. However, plant tissue culture may generate genetic variability, i.e., somaclonal variations as a result of gene mutation or changes in epigenetic marks. The occurrence of subtle somaclonal variation is a drawback for both in vitro cloning as well as germplasm preservation. Therefore, it is of immense significance to assure the genetic uniformity of in vitro raised plants at an early stage. Several strategies have been followed to ascertain the genetic fidelity of the in vitro raised progenies comprising morpho-physiological, biochemical, cytological and DNA-based molecular markers approaches. Somaclonal variation can pose a serious problem in any micropropagation program, where it is highly desirable to produce true-to-type plant material. On the other hand, somaclonal variation has provided a new and alternative tool to the breeders for obtaining genetic variability relatively rapidly and without sophisticated technology in horticultural crops, which are either difficult to breed or have narrow genetic base. In the present paper, sources of variations induced during tissue culture cycle and strategies to ascertain and confirm genetic fidelity in a variety of in vitro raised plantlets and potential application of variants in horticultural crop improvement are reviewed.

/pdf/somaclonal-variations-and-their-applications-in-34x0z8l3la.pdf

Somaclonal variations and their applications in horticultural crops improvement

Micropropagation of orchids: A review on the potential of different explants

Tissue culture of ornamental pot plant: A critical review on present scenario and future prospects

Efficient protocols of axillary bud multiplication and indirect organogenesis were established for Holostemma ada-kodien Schult. (Asclepiadaceae). Murashige and Skoog (MS) medium supplemented with 2.0 mg l–1 N6-benzylaminopurine (BAP) and 0.5 mg l–1 indole-3-butyric acid (IBA) induced an average of eight shoots per node and was the best for axillary bud proliferation. Subsequent cultures enhanced the number of shoots. The explant source of callus and the growth regulator inducing the callus exhibited significant influence on organogenesis. Callus developed from the basal cut end of the node explants differentiated more than 15 shoots on MS medium fortified with 1.5 mg l–1BAP. Callus from internode explants developed fewer shoots than callus from the basal cut ends of node explants. Leaf-derived callus did not undergo organogenesis. The abscission of leaves and shoot tips of the developed shoots was prevented by the addition of AgNO3 or CoCl2, but with a concomitant significant reduction in the number of shoots. Half-strength solid MS or liquid medium with 0.05 mg l–1 IBA exhibited the best in vitro rooting. Ninety percent of the rooted shoots survived in the field.

Rapid propagation of Holostemma ada-kodien Schult., a rare medicinal plant, through axillary bud multiplication and indirect organogenesis

Rapid in vitro propagation of Dendrobium hybrids through direct shoot formation from foliar explants, and protocorm-like bodies

Single medium-based efficient protocols for large-scale multiplication of the rare woody aromatic medicinal plant Rotula aquatica Lour. by means of axillary bud multiplication and indirect organogenesis were established using Murashige and Skoog (MS) medium. There were no significant differences with respect to the induction of shoots per node or callus and roots per shoot on media prepared either with tap water and commercial sugar or those prepared with double distilled water and tissue culture-grade sucrose. The most effective medium for axillary bud proliferation was MS medium fortified with 1.0 mg l–1 N6-benzylaminopurine (BAP) and 0.5 mg l–1 indole-3-butyric acid (IBA), on which shoots were induced at the rate of 15 per node. The excision of node segments from the in vitro-derived shoots and their subsequent culture on medium supplemented with same concentrations of BAP and IBA facilitated enhanced axillary bud proliferation. Callus that developed from the lower cut end of the node explants induced shoots during subculture on half-strength MS medium with 1.0 mg l–1 BAP and 0.5 mg l–1 kinetin. The shoots developed rooted best on half-strength MS medium supplemented with 0.5 mg l–1 naphthaleneacetic acid (NAA). Rooted shoots, following acclimation in the greenhouse, were successfully transferred to field conditions, and 80% of the plantlets survived. When the basal ends of shoots harvested from multiplication medium were dipped in an NAA (0.5 mg l–1) solution for 25 days, a mean of 5.6 roots per shoot developed; the transfer to small pots facilitated the survival of 75% of the rooted shoots. Ex vitro rooting by direct transfer of the shoots from the multiplication medium to the greenhouse resulted in a 65% survival. Commercial sugar and tap water and ex vitro rooting make the protocol economically advantageous. About 750 plantlets were procured in a 3-month period starting from a single node explant.

Rapid in vitro multiplication and ex vitro rooting of Rotula aquatica Lour., a rare rhoeophytic woody medicinal plant.

Protocol for rapid in vitro propagation of Ceropegia candelabrum L. (Asclepiadaceae) through axillary bud multiplication was established. Murashige and Skoog (MS) medium with 8.87 μM N
6-benzyladenine (BA) and 2.46 μM indole-3-butyric acid (IBA) was best suited for axillary bud proliferation inducing a mean of eight shoots / node. Excision and culture of the nodal segments from the in vitro shoots on fresh medium with same concentrations of BA and IBA facilitated development of more than 10 shoots / node. Subsequent cultures enhanced the rate of shoot proliferation. Shoots developed were rooted best on half strength MS with 0.49 μM IBA. Starting from a single node explant, 250 rooted shoots were obtained within 120 days. Plantlets established in pots exhibited 90% survival. Plantlets successfully established in field exhibited morphological characters identical to mother plants.

Rapid in vitro propagation of medicinally important Ceropegia candelabrum

A morphological variant obtained from in vitro corm-derived plants of banana (Musa sp.) cv. Grande Naine (AAA) was evaluated up to harvest, and the genetic basis of variation was confirmed by the random amplified polymorphic DNA (RAPD). The corms formed during the multiplication phase of shoot tip-derived cultures of the cv. Grande Naine grown on Murashige and Skoog (MS) medium enriched with 13.3 μM N6-benzyladenine (BA) developed numerous morphological variants after transfer to MS medium with 6.66 μM BA. The variant designated as CUDBT-B1, with distinct morphological features, was further evaluated. The morphological features of CUDBT-B1 were variegated leaf, pseudostem, bracts, ovary of the male flower and fruits, reduced height, decreased lamina length and breadth, and early flowering. These features were also manifested in the second-cycle progeny of CUDBT-B1. RAPD assay showed a marker DNA band of 1650 bp, and differential band intensity between the CUDBT-B1 and normal clone. CUDBT-B1 was m...

K. P. Martin

Papers

Rapid propagation of Holostemma ada-kodien Schult., a rare medicinal plant, through axillary bud multiplication and indirect organogenesis

Rapid in vitro propagation of Dendrobium hybrids through direct shoot formation from foliar explants, and protocorm-like bodies

Rapid in vitro multiplication and ex vitro rooting of Rotula aquatica Lour., a rare rhoeophytic woody medicinal plant.

Rapid in vitro propagation of medicinally important Ceropegia candelabrum

RAPD analysis of a variant of banana ( Musa sp.) cv. grande naine and its propagation via shoot tip culture