Judit Dobránszki

Micropropagation of apple — A review

Micropropagation of apple has played an important role in the production of healthy, disease-free plants and in the rapid multiplication of scions and rootstocks with desirable traits. During the last few decades, in apple, many reliable methods have been developed for both rootstocks and scions from a practical, commercial point of view. Successful micropropagation of apple using pre-existing meristems (culture of apical buds or nodal segments) is influenced by several internal and external factors including ex vitro (e.g. genotype and physiological state) and in vitro conditions (e.g., media constituents and light). Specific requirements during stages of micropropagation, such as the establishment of in vitro cultures, shoot multiplication, rooting of microshoots and acclimatization are summarized in this review. New approaches for increasing shoot multiplication and rooting for apple and current use of micropropagated plantlets as tools in basic and applied research are also discussed.

The role of cytokinins in shoot organogenesis in apple

Effective regeneration in vitro is a necessary precondition for the implementation of different biotechnological approaches in plant breeding. Numerous studies have reported on regeneration from apple somatic tissues, and organogenesis has been proved to be influenced by several factors including mother shoots (genotype, size, type, and age of explant), in vitro conditions (dark period, light intensity, and quality), and others (wounding, orientation of leaf explants). However, one of the most important factors before and during the regeneration process is the type and concentration of cytokinin applied. Thidiazuron and benzyladenine are the most frequently used cytokinins in the regeneration systems, but their efficiency depends on genotype and other factors. Other cytokinins (e.g., zeatin and kinetin) have also been tested in several experiments and they were found in general to be less active. The organogenic ability of explants can also be increased by a properly selected cytokinin pre-treatment. Cytokinins applied in the pre-treatments can influence the leaf structure, which in turn can alter the regeneration capacity of the leaf explant. Interactions between factors of pre-treatments (hormones, light, and culture conditions) and factors of the regeneration phase should be considered. This review brings into focus the role of different cytokinins during in vitro shoot development, discussing their effects on the histology of leaves developed in vitro, and how this affects the subsequent regeneration process.

Problems with Traditional Science Publishing and Finding a Wider Niche for Post-Publication Peer Review

Science affects multiple basic sectors of society. Therefore, the findings made in science impact what takes place at a commercial level. More specifically, errors in the literature, incorrect findings, fraudulent data, poorly written scientific reports, or studies that cannot be reproduced not only serve as a burden on tax-payers’ money, but they also serve to diminish public trust in science and its findings. Therefore, there is every need to fortify the validity of data that exists in the science literature, not only to build trust among peers, and to sustain that trust, but to reestablish trust in the public and private academic sectors that are witnessing a veritable battle-ground in the world of science publishing, in some ways spurred by the rapid evolution of the open access (OA) movement. Even though many science journals, traditional and OA, claim to be peer reviewed, the truth is that different levels of peer review occur, and in some cases no, insufficient, or pseudo-peer review takes place. This ultimately leads to the erosion of quality and importance of science, allowing essentially anything to become published, provided that an outlet can be found. In some cases, predatory OA journals serve this purpose, allowing papers to be published, often without any peer review or quality control. In the light of an explosion of such cases in predatory OA publishing, and in severe inefficiencies and possible bias in the peer review of even respectable science journals, as evidenced by the increasing attention given to retractions, there is an urgent need to reform the way in which authors, editors, and publishers conduct the first line of quality control, the peer review. One way to address the problem is through post-publication peer review (PPPR), an efficient complement to traditional peer-review that allows for the continuous improvement and strengthening of the quality of science publishing. PPPR may also serve as a way to renew trust in scientific findings by correcting the literature. This article explores what is broadly being said about PPPR in the literature, so as to establish awareness and a possible first-tier prototype for the sciences for which such a system is undeveloped or weak.

Phloroglucinol in plant tissue culture

In plant tissue culture research, there is a constant need to search for novel substances that could result in better or more efficient growth in vitro. A relatively unknown compound, phloroglucinol (1,3,5-trihydroxybenzene), which is a degradation product of phloridzin, has growth-promoting properties. Phloroglucinol increases shoot formation and somatic embryogenesis in several horticultural and grain crops. When added to rooting media together with auxin, phloroglucinol further stimulates rooting, most likely because phloroglucinol and its homologues act as auxin synergists or auxin protectors. Of particular interest is the ability of phloroglucinol—a precursor in the lignin biosynthesis pathway—to effectively control hyperhydricity through the process of lignification, thus maximizing the multiplication rate of woody species and other species that are difficult to propagate. Phloroglucinol has also been used to improve the recovery of cryopreserved Dendrobium protocorms, increasing the potential of cryopreservation for application in ornamental biotechnology. Phloroglucinol demonstrates both cytokinin-like and auxin-like activity, much like thidiazuron, and thus has considerable potential for application in a wide range of plant tissue culture studies.

Symbiotic in vitro seed propagation of Dendrobium: fungal and bacterial partners and their influence on plant growth and development

The genus Dendrobium is one of the largest genera of the Orchidaceae Juss. family, although some of its members are the most threatened today. The reason why many species face a vulnerable or endangered status is primarily because of anthropogenic interference in natural habitats and commercial overexploitation. The development and application of modern techniques and strategies directed towards in vitro propagation of orchids not only increases their number but also provides a viable means to conserve plants in an artificial environment, both in vitro and ex vitro, thus providing material for reintroduction. Dendrobium seed germination and propagation are challenging processes in vivo and in vitro, especially when the extreme specialization of these plants is considered: (1) their biotic relationships with pollinators and mycorrhizae; (2) adaptation to epiphytic or lithophytic life-styles; (3) fine-scale requirements for an optimal combination of nutrients, light, temperature, and pH. This review also aims to summarize the available data on symbiotic in vitro Dendrobium seed germination. The influence of abiotic factors as well as composition and amounts of different exogenous nutrient substances is examined. With a view to better understanding how to optimize and control in vitro symbiotic associations, a part of the review describes the strong biotic relations of Dendrobium with different associative microorganisms that form microbial communities with adult plants, and also influence symbiotic seed germination. The beneficial role of plant growth-promoting bacteria is also discussed.

Sonication and ultrasound: impact on plant growth and development

Plant biotechnology, and plant tissue culture in particular, could benefit from new means to stimulate plant growth and development. Although the number of studies is still limited, there is evidence that sonication using low frequencies of sound (as little as a few dozen Hz) to as high as ultrasound (several dozen kHz) may increase organogenesis. In this brief review, we look at those examples in detail and explore how sound influences growth and development. Where available, we try to offer a mechanism by which sound affects or influences plant growth.

Dendrobium micropropagation: a review

Dendrobium is one of the largest and most important (ornamentally and medicinally) orchid genera. Tissue culture is now an established method for the effective propagation of members of this genus. This review provides a detailed overview of the Dendrobium micropropagation literature. Through a chronological analysis, aspects such as explant, basal medium, plant growth regulators, culture conditions and final organogenic outcome are chronicled in detail. This review will allow Dendrobium specialists to use the information that has been documented to establish, more efficiently, protocols for their own germplasm and to improve in vitro culture conditions based on the optimized parameters detailed in this review. Not only will this expand the use for mass propagation, but will also allow for the conservation of important germplasm. Information on the in vitro responses of Dendrobium for developing efficient protocols for breeding techniques based on tissue culture, such as polyploidization, somatic hybridization, isolation of mutants and somaclonal variants and for synthetic seed and bioreactor technology, or for genetic transformation, is discussed in this review. This is the first such review on this genus and represents half a decade of literature dedicated to Dendrobium micropropagation.

In vitro flowering of Dendrobium

Dendrobium plants are the most frequently used orchids to study the process of in vitro flowering. Among the various environmental cues and plant growth regulators employed thus far, cytokinins have shown the most prominent effects on the transition from vegetative to reproductive stage. A clear correlation between flowering establishment and enhancement of endogenous cytokinins has been observed. However, the experimental utilization of a large amount of different Dendrobium species and hybrids, combined with a large diversity of variable media types and media compositions make interpretation of flowering control in the in vitro environment difficult. The combination of a specific model Dendrobium in vitro regeneration system or protocol with a simple, but well defined culture medium, could contributed, to some degree, to reaching a clearer consensus about the physiological and molecular mechanisms controlling the Dendrobium flowering phase change.

Cytokinin-induced changes in the chlorophyll content and fluorescence of in vitro apple leaves.

Cytokinins (CKs) are one of the main regulators of in vitro growth and development and might affect the developmental state and function of the photosynthetic apparatus of in vitro shoots. Effects of different cytokinin regimes including different types of aromatic cytokinins, such as benzyl-adenine, benzyl-adenine riboside and 3-hydroxy-benzyladenine alone or in combination were studied on the capacity of the photosynthetic apparatus and the pigment content of in vitro apple leaves after 3 weeks of culture. We found that the type of cytokinins affected both chlorophyll a and b contents and its ratio. Chlorophyll content of in vitro apple leaves was the highest when benzyl-adenine was applied as a single source of cytokinin in the medium (1846-2176 μg/1g fresh weight (FW) of the leaf). Increasing the concentration of benzyl-adenine riboside significantly decreased the chlorophyll content of the leaves (from 1923 to 1183 μg/1g FW). The highest chl a/chl b ratio was detected after application of meta-topolin (TOP) at concentrations of 2.0 and 6.0 μM (2.706 and 2.804). Chlorophyll fluorescence was measured both in dark-adapted (Fv/Fm test) and in light-adapted leaf samples (Yield test; Y(II)). The maximum quantum yield and efficiency of leaves depended on the cytokinin source of the medium varied between 0.683 and 0.861 (Fv/Fm) indicating a well-developed and functional photosynthetic apparatus. Our results indicate that the type and concentration of aromatic cytokinins applied in the medium affect the chlorophyll content of the leaves in in vitro apple shoots. Performance of the photosynthetic apparatus measured by chlorophyll fluorescence in the leaves was also modified by the cytokinin supply. This is the first ever study on the relationship between the cytokinin supply and the functionability of photosystem II in plant tissue culture and our findings might help to increase plantlet survival after transfer to ex vitro conditions.

Advances in Dendrobium molecular research: Applications in genetic variation, identification and breeding.

Orchids of the genus Dendrobium are of great economic importance in global horticultural trade and in Asian traditional medicine. For both areas, research yielding solid information on taxonomy, phylogeny, and breeding of this genus are essential. Traditional morphological and cytological characterization are used in combination with molecular results in classification and identification. Markers may be useful when used alone but are not always reliable in identification. The number of species studied and identified by molecular markers is small at present. Conventional breeding methods are time-consuming and laborious. In the past two decades, promising advances have been made in taxonomy, phylogeny and breeding of Dendrobium species due to the intensive use of molecular markers. In this review, we focus on the main molecular techniques used in 121 published studies and discuss their importance and possibilities in speeding up the breeding of new cultivars and hybrids.