Oil palm, a tropical plant with an economic life of 20-25 years, is on high demand since its oil (palm oil) is now considered to be the world's most consumed oil. Despite the high potential for the use of clonal materials, the tissue culture technique for oil palm is difficult and laborious. One of the key steps of the process is the conversion of polyembroids into plantlets. Gelling agent has been implicated to play a role in ensuring the conversion of oil palm polyembryoids into complete plantlets. In the present study, for the first time, we report the effects of two types of common gelling agents, Agar Type 900 and Gelrite®, for enhanced conversion of oil palm polyembryoids into plantlets. Polyembryoids, developed from embryonic calli, were cultured and incubated on Murashige and Skoog semisolid media supplemented with Agar (Type 900) at 8-12 g/l or gellan gum (Gelrite®) 1.5-3.5 g/l. The effects of gelling agents on polyembryoid conversion was assessed based on the percentages of viability, survival, and polyembryoids that swelled, enlarged, and turned green, as well as on the basis of morphological characteristics, viz, number of shoots, leaves, roots, secondary somatic embryos, and callus formation. Based on the results of this study, in comparison to Agar Type 900, the Gelrite® with 3.5 g/l concentration was chosen as an effective gelling agent for conversion of polyembryoids into plantlets, since it resulted in 100% survival with 53.3% completely developed plantlets (multiple shoots with roots). The successful conversion of polyembryoids into plantlets achieved in this study, using the optimized gelling agent could be useful for pre-storage or post-storage conversion in many other plant species as well.
There is an ample genetic diversity of plants with medicinal importance around the globe and this pool of genetic variation serves as the base for selection as well as for plant improvement. Thus, identification, characterization and documentation of the gene pool of medicinal plants are essential for this purpose. Genomic information of many a medicinal plant species has increased rapidly since the past decade and genetic resources available for domestication and improvement programs include genome sequencing, expressed sequence tags sequencing, transcript profiling, gene transmit, molecular markers in favor of mapping and breeding. In recent years, multiple endeavors have been undertaken for genomic characterization of medicinal plant species with the aid of molecular markers for sustainable utilization of gene pool, its conservation and future studies. Recent advancement in genomics is so fast that only some researches have been published till date and to a large extent documentation is restricted to electronic resources. Whole genome profiling of the identified medicinal plant species, carried out by several researchers, based on the DNA fingerprinting, is well documented in the present review. This review will facilitate preparing a database of the widely used, economically important medicinal plant species, based on their genomic organization.
The present investigation was carried out to evaluate 33 rice landrace genotypes for assessment of their salt tolerance at seedling stage. Growth parameters like root length, shoot length and plant biomass were measured after 12 days of exposure to six different levels of saline solution (with electrical conductivity of 4, 6, 8, 10, 12 or 14 dS m (-1)). Genotypes showing significant interaction and differential response towards salinity were assessed at molecular level using 11 simple sequence repeats (SSR) markers, linked with salt tolerance quantitative trait loci. Shoot length, root length and plant biomass at seedling stage decreased with increasing salinity. However, relative salt tolerance in terms of these three parameters varied among genotypes. Out of the 11 SSR markers RM8094, RM336 and RM8046, the most competent descriptors to screen the salt tolerant genotypes with higher polymorphic information content coupled with higher marker index value, significantly distinguished the salt tolerant genotypes. Combining morphological and molecular assessment, four lanraces viz. Gheus, Ghunsi, Kuthiahara and Sholerpona were considered as true salt tolerant genotypes which may contribute in greater way in the development of salt tolerant genotypes in rice.
In the present study, polyembryoids of oil palm (Elaeis guineensis Jacq.) were cryopreserved with successful revival of 68 % for the first time using the droplet vitrification technique. Excised polyembryoids (3-5-mm diameter) from 3-month-old in vitro cultures were pre-cultured for 12 h in liquid Murashige and Skoog medium supplemented with 0.5 M sucrose. The polyembryoids were osmoprotected in loading solution [10% (w/v) dimethyl sulphoxide (DMSO) plus 0.7 M sucrose] for 30 min at room temperature and then placed on aluminium strips where they were individually drenched in chilled droplets of vitrification solution (PVS2) [30% (w/v) glycerol plus 15% (w/v) ethylene glycol (EG) plus 15% (w/v) DMSO plus 0.4 M sucrose] for 10 min. The aluminium strips were enclosed in cryovials which were then plunged quickly into liquid nitrogen and kept there for 1 h. The polyembryoids were then thawed and unloaded (using 1.2 M sucrose solution) with subsequent transfer to regeneration medium and stored in zero irradiance. Following for 10 days of storage, polyembryoids were cultured under 16 h photoperiod of 50 μmol m(-2) s(-1) photosynthetic photon flux density, at 23 ± 1 °C. Post-thaw growth recovery of 68% was recorded within 2 weeks of culture, and new shoot development was observed at 4 weeks of growth. Scanning electron microscopy revealed that successful regeneration of cryopreserved polyembryoids was related to maintenance of cellular integrity, presumably through PVS2 exposure for 10 min. The present study demonstrated that cryopreservation by droplet vitrification enhanced the regeneration percentages of oil palm in comparison with the conventional vitrification method previously reported.
Plants tend to acclimatize to unfavourable environs by integrating growth and development to environmentally activated signals. Phytohormones strongly regulate convergent developmental and stress adaptive procedures and synchronize cellular reaction to the exogenous and endogenous conditions within the adaptive signaling networks. Gibberellins (GA), a group of tetracyclic diterpenoids, being vital regulators of plant growth, are accountable for regulating several aspects of growth and development of higher plants. If the element of reproduction is considered as an absolute requisite then for a majority of the higher plants GA signaling is simply indispensable. Latest reports have revealed unique conflicting roles of GA and other phytohormones in amalgamating growth and development in plants through environmental signaling. Numerous physiological researches have detailed substantial crosstalk between GA and other hormones like abscisic acid, auxin, cytokinin, and jasmonic acid. In this review, a number of explanations and clarifications for this discrepancy are explored based on the crosstalk among GA and other phytohormones.
The current report assesses the efficiency of encapsulation-desiccation protocol to cryopreserve oil palm (Elaeis guineensis Jacq.) polyembryoids. Specifically identified polyembryoids, comprising of haustorium and torpedo-shaped structures, were encapsulated [comprising 3% (w/v) sodium alginate and 100 mM CaCl2]. Calcium alginate-encapsulated and sucrose-precultured polyembryoids were subjected to different spans of desiccation in a laminar air-flow cabinet, followed by freezing in liquid nitrogen. The effect of sucrose preculture (with gradual exposure to 0.3, 0.5, 0.75 and 1 M for 7 days) and dehydration periods (0-10 h) under sterile air-flow on post-freezing survival and regrowth of encapsulated polyembryoids were studied. Cryopreserved and thawed polyembryoids (initially precultured in sucrose, followed by 9 h air-desiccated to 23.3% moisture content) displayed the highest survival percentage (73.3%) and regeneration (of shoot, root and secondary somatic embryo) on Murashige and Skoog regrowth medium containing sucrose (0.3-1 M) and 0.2 mg/l 2,4-dichlorophenoxy acetic acid. In addition, ultrastructural study using scanning electron microscopy exhibited successful revival of cryopreserved polyembryoids, owing to retention of cellular membrane stability through optimized and protected (encapsulated) desiccation. The present study thus substantiates the potential of this encapsulation-desiccation procedure in cryopreservation of oil palm polyembryoids for long-term conservation programs.
Genetic diversity represents the heritable variation both within and among populations of organisms, and in the context of this paper, among bamboo species. Bamboo is an economically important member of the grass family Poaceae, under the subfamily Bambusoideae. India has the second largest bamboo reserve in Asia after China. It is commonly known as "poor man's timber", keeping in mind the variety of its end use from cradle to coffin. There is a wide genetic diversity of bamboo around the globe and this pool of genetic variation serves as the base for selection as well as for plant improvement. Thus, the identification, characterization and documentation of genetic diversity of bamboo are essential for this purpose. During recent years, multiple endeavors have been undertaken for characterization of bamboo species with the aid of molecular markers for sustainable utilization of genetic diversity, its conservation and future studies. Genetic diversity assessments among the identified bamboo species, carried out based on the DNA fingerprinting profiles, either independently or in combination with morphological traits by several researchers, are documented in the present review. This review will pave the way to prepare the database of prevalent bamboo species based on their molecular characterization.
Date palm (Phoenix dactylifera L.) is one of the most important fruit trees that contribute a major part to the economy of Middle East and North African countries. It is quintessentially called "tree of life" owing to its resilience to adverse climatic conditions, along with manifold nutritional-cum-medicinal attributes that comes from its fruits and other plant parts. Being a tree with such immense utility, it has gained substantial attention of tree breeders for its genetic advancement via in vitro biotechnological interventions. Herein, an extensive review of biotechnological research advances in date palm has been consolidated as one of the major research achievements during the past two decades. This article compares the different biotechnological techniques used in this species such as: tissue and organ culture, bioreactor-mediated large-scale propagation, cell suspension culture, embryogenic culture, protoplast culture, conservation (for short- and long-term) of germplasms, in vitro mutagenesis, in vitro selection against biotic and abiotic stresses, secondary metabolite production in vitro, and genetic transformation. This review provides an insight on crop improvement and breeding programs for improved yield and quality fruits; besides, it would undeniably facilitate the tissue culture-based research on date palm for accelerated propagation and enhanced production of quality planting materials, along with conservation and exchange of germplasms, and genetic engineering. In addition, the unexplored research methodologies and major bottlenecks identified in this review should be contemplated on in near future.