Rakhi Chaturvedi

Endosperm culture: a novel method for triploid plant production

Triploid nature of endosperm is the characteristic feature of angiosperms and is formed as a result of triple fusion. Present review discusses the morphogenic response and production of triploid plantlets by endosperm culture. Both mature and immature endosperm used for culture initiation responded differently in cultures. A key factor for the induction of cell divisions in mature endosperm cultures is the initial association of embryo but immature endosperms proliferate independent of embryo. In almost all the parasitic angiosperms, endosperm shows a tendency of direct differentiation of organs without prior callusing, whereas in autotrophic taxa the endosperm usually forms callus tissue followed by differentiation of shoot buds, roots or embryos. The endosperm tissue often shows a high degree of chromosomal variations and polyploidy. Mitotic irregularities, chromosome bridges and laggards are the other important characteristics of endosperm tissues. Triploids are usually seed sterile and is undesirable for plants where seeds are commercially useful. However, in cases where seedlessness is employed to improve the quality of fruits as in banana, apple, citrus, grapes, papaya etc. the induction of triploid plants would be of immense use. Triploid plants have more vigorous vegetative growth than their diploid counterparts. Hence, in plants where the vegetative parts are economically useful, triploids are of good use. This review focuses on the progress achieved so far in endosperm culture to obtain triploid plants.

High-frequency shoot regeneration from cotyledon explants of watermelon cv. sugar baby

SummaryA protocol for in vitro shoot regeneration from cotyledon explants of Citrullus lanatus (Thunb.) Matsum. & Nakai cv. Sugar Baby is described. The cotyledons excised from 7-d-old aseptic seedlings showed the highest percentage of shoots on Murashige and Skoog (MS) + N6-benzyladenine (BA; 3.0 μM) + N6-[2-isopentenyl] adenine (2iP; 3.0 μM) and MS + BA (3.0 μM) + indole-3-acetic acid (IAA; 3.0 μM). Whereas the latter medium induced shoot regeneration after the callusing of the explant, the former stimulated direct shoot formation. The regenerated shoots were rooted and the resulting plants were established in earthen pots with 55% success.

In vitro androgenesis in tree species : An update and prospect for further research

Most, if not all, trees are outbreeding, highly heterozygous and undergo a long developmental period before reaching their reproductive stage. Classical breeding and cross-pollinating procedures are both unpredictable and time-consuming. In vitro androgenesis is, thus, the most prolific and desirable approach of haploid production. But various attempts to induce androgenic potential in the trees have met with rather limited success, as they ought to be extremely recalcitrant in culture. The success rate in this case is nowhere close to that achieved for some model species like Brassica and Nicotiana. Our review article intends to focus on the overview of androgenic process and all the major contributions till date on tree species with regard to this aspect. We wish to bring together in one place all the important variables used by different workers, that influence androgenic potential immensely like, stage of anther or microspore at culture, media composition, combinations and concentrations of growth regulators, and additives. This will prove to be a worthy guide to all the prospective workers in this area and in designing their experiments further.

An efficient protocol for the production of triploid plants from endosperm callus of neem, Azadirachta indica A. Juss.

Triploid plants of neem were obtained by immature endosperm culture. Immature seeds, at the early dicotyledonous stage of embryo development, is the best explant to raise endosperm callus on MS + NAA (5 mumol/L) + BAP (2 mumol/L) + CH (500 mg L-1). Maximum shoot bud differentiation from the endosperm callus occurred on MS + 5 mumol/L BAP. Shoots were multiplied by forced axillary branching and rooted in vitro. The plants were established in soil. Over 66% of the plants were triploid with chromosome number 2n = 3x = 36. A characteristic feature of the shoots of endosperm origin is the presence of a large number of multi-cellular glands.

In vitro morphogenesis in zygotic embryo cultures of neem (Azadirachta indica A. Juss.)

Immature zygotic embryo cultures of neem yielded highly regenerative cultures, with the response varying with the embryo stage at culture. Early dicotyledonous stage embryos were the most responsive followed by torpedo stage embryos. The embryo cultures differentiated three types of regenerants: somatic embryos (SEs), shoot buds and neomorphs. SEs exhibited morphological abnormalities such as pluricotyledony, fusion of cotyledons and absence of cotyledons. Although these SEs showed secondary embryogenesis, the occurrence of normal dicotyledonous embryos was extremely rare. On MS basal medium 3% of SEs developed a long tap root but a plumular shoot did not appear. However, it was possible to regenerate plantlets from immature zygotic embryo cultures of neem via neomorph formation and adventitious shoot bud formation. The transplantation survival of these plants was more than 80%.

Increased production of azadirachtin from an improved method of androgenic cultures of a medicinal tree Azadirachta indica A. Juss

This report is the first direct evidence of azadirachtin production in androgenic haploid cultures of Azadirachta indica, a woody medicinal tree. Anther cultures at early-late-uninucleate stage of microspores were established on MS medium with BAP (5 µM), 2,4-D (1 µM) and NAA (1 µM) containing 12% sucrose. The calli, induced, were further multiplied on 2,4-D and Kinetin media. Shoots, differentiated on BAP (2.2 µM) + NAA (0.05 µM) medium, were elongated on MS + BAP (0.5 µM) and multiplied on MS + BAP (1 µM) + CH (250 mg/l). Thereafter, the shoots were rooted on 1/4 MS + IBA (0.5 µM). Cytological analysis of the calli and regenerants have confirmed their haploid status with the chromosome number as 2n=x=12. The haploid cell lines and leaves from in vitro grown plantlets were analyzed for azadirachtin by RP-HPLC and mass spectroscopy. Maximum azadirachtin (728.41 µg/g DW) was detected in calli supporting best shoot proliferation while least (49 µg/g DW) was observed in an undifferentiated line from maintenance medium. This study has brought us a step closer to develop genetically pure lines that could serve as new and attractive alternative ways of homogeneous controlled production of high value compounds, round the year, independent of geographical and climatic barrier.

Sustainable production of azadirachtin from differentiated in vitro cell lines of neem (Azadirachta indica)

Neem possesses immense medicinal properties and has immediate application as ecofriendly, biodegradable biopesticide. All these properties are because of a structurally complex bioactive compound Azadirachtin, mainly present in seeds. However, it could not be exploited to its full because of heterogeneity in compound production due to out-breeding in nature of the plant. This is the first elaborate report on systematic studies on azadirachtin biosynthesis where different redifferentiated and dedifferentiated in vitro cell lines of A. indica (neem), obtained from various explants, were utilized. All cell lines were found positive for the compound with significantly higher azadirachtin yield of 2330 µg /g DW was obtained from redifferentiated cell lines established from zygotic embryo cultures. The study, demonstrates the possibility of consistent biosynthesis of azadirachtin in bulk under optimal growth conditions.

Establishment of dedifferentiated callus of haploid origin from unfertilized ovaries of tea (Camellia sinensis (L.) O. Kuntze) as a potential source of total phenolics and antioxidant activity

In the HTML version, the correct names of the authors are Rashmi Rekha Hazarika and Rakhi Chaturvedi.

Extracts of dedifferentiated cultures of Spilanthes acmella Murr. possess antioxidant and anthelmintic properties and hold promise as an alternative source of herbal medicine

This study reports the antioxidant and anthelmintic activities of Spilanthes cell cultures. Murashige and Skoog medium supplemented with 5.0 μM N6-benzylaminopurine, 1.0 μM 2,4-dichlorophenoxyacetic acid and 1.0 μM α-naphthaleneacetic acid was found to be the best medium to induce dedifferentiation from the leaf cells and for further maintenance of the callus cultures. These cell cultures and in vivo leaves were subjected to solvent extraction by hexane, ethyl acetate, methanol and water, and their extraction yield and total phenolic contents were evaluated. The antioxidant activity of extracts was determined by using 2,2-diphenyl-1-picrylhydrazyl free radical scavenging assay. The methanol extracts of in vitro callus and in vivo leaf showed an apparent antioxidant activity and their IC50 values were 1342.9 and 1085.1 μg/ml, respectively. The anthelmintic efficacy of the extracts was also tested using live trematode (fluke) parasites of cattle as the model test material. The aqueous extract of dedifferentiated callus showed a strong anthelmintic activity, which was higher than the activity of the water extract of the field-grown plant. The results of this study verify the potential of Spilanthes as a reservoir of bioactive agents and also substantiate the value of callus cultures as a new source of anthelmintic and antioxidant compounds.

Evaluation of Cr(VI) Exposed and Unexposed Plant Parts of Tradescantia pallida (Rose) D. R. Hunt. for Cr Removal from Wastewater by Biosorption

Phytoremediation is an efficient method for the removal of heavy metals from contaminated systems. A productive disposal of metal accumulating plants is a major concern in current scenario. In this work, Cr(VI) accumulating Tradescantia pallida plant parts were investigated for its reuse as a biosorbent for the removal of Cr(VI) ions. The effect of pH, contact time, sorbent dosage, Cr(VI) concentration and temperature was examined to optimize these process parameters. Results showed that Cr(VI) exposed/unexposed T. pallida leaf biomass could remove 94% of chromium with a sorption capacity of 64.672 mg g−1. Whereas the kinetics of Cr(VI) biosorption was well explained by the pseudo second-order kinetic model, the Langmuir model better described the data on Cr(VI) sorption isotherm compared with the Freundlich model. The changes in the free energy (ΔG°), entropy (ΔS°) and enthalpy (ΔH°) were found to be −5.276 kJ mol−1, 0.391 kJ mol−1 K−1 and 11.346 kJ mol−1, respectively, which indicated the process to be spontaneous, feasible and endothermic in nature. FTIR spectra of T. pallida leaf biomass revealed the active participation of ligands, such as −NH, amide, hydroxyl and sulphonate groups present in the biomass for Cr(VI) binding, SEM analysis revealed a porous structure of the biosorbent for an easy uptake of Cr(VI).