Yaser Hassan Dewir

In vitro rooting of leguminous plants: Difficulties, alternatives, and strategies for improvement

Leguminous plants include many of the most important food crops and are also cultivated for forage, used as a rich fiber source, and are important in the manufacture of pharmaceutical compounds. Their ability to biologically fix atmospheric nitrogen enhances soil fertility. Beyond conventional propagation methods, modern in vitro technology offers new means for propagating these plants. Significant progress has been achieved in somatic embryogenesis and embryo rescue, despite legumes’ notorious recalcitrance to transformation and regeneration of legumes. The establishment of stable and reproducible regeneration protocols has resulted in commercially successful propagation of some legume species. Still, regeneration protocols for many other legumes have not been successful, primarily due to poor in vitro rooting during regeneration. This review addresses the factors constraining rooting, describes alternative methods to promote in vitro rooting, and provides a summary of in vitro rooting studies performed across a large number of leguminous species.

Photosynthetic and biochemical characterization of in vitro-derived African violet (Saintpaulia ionantha H. Wendl) plants to ex vitro conditions

African violet (Saintpaulia ionantha H. Wendl) is one of the most easily and commonly tissue-cultured ornamental plants. Despite this, there are limited reports on photosynthetic capacity and its impact on the plant quality during acclimatization. Various growth, photosynthetic and biochemical parameters and activities of antioxidant enzymes and dehydrins of micropropagated plants were assessed under three light intensities (35, 70, and 100 µmol m−2 s−1 photosynthetic photon flux density – PPFD). Fresh and dry plant biomass, plant height, and leaf area were optimal with high irradiance (70–100 µmol m−2 s−1 PPFD). Chlorophyll and carotenoid contents and net photosynthesis were optimal in plants grown under 70 µmol m−2 s−1 PPFD. Stomatal resistance, malondialdehyde content, and Fv/Fm values were highest at low light irradiance (35 µmol m−2 s−1 PPFD). The activities of three antioxidant enzymes, superoxide dismutase, catalase, and glutathione peroxidase, increased as light irradiance increased, signaling that high light irradiance was an abiotic stress. The accumulation of 55, 33, and 25 kDa dehydrins was observed with all light treatments although the expression levels were highest at 35 µmol m−2 s−1 PPFD. Irradiance at 70 µmol m−2 s−1 PPFD was suitable for the acclimatization of African violet plants. Both low and high irradiance levels (35 and 100 µmol m−2 s−1 PPFD) induced the accumulation of antioxidants and dehydrins in plants which reveals enhanced stress levels and measures to counter it.

Micropropagation of Cattleya: Improved in vitro rooting and acclimatization

The present study reports optimization of in vitro rooting of Cattleya shoots with the aim to increase survival rate during acclimatization. Shoots (2.0–2.5 cm) which were regenerated in vitro were cultured on Murashige and Skoog (MS) medium and the effect of various parameters such as type and concentration of auxin [0.3, 0.6, 1.2 and 2.4 mg·L−1 indole butyric acid (IBA) and naphthaleneacetic acid (NAA)], medium strength (full and half strength), sucrose concentration (0, 15 and 30 g·L−1) and light intensity [photosynthetic photon flux density (PPFD) of 30, 60, 90 μmol·m−2·s−1] were tested. Half strength MS medium supplemented with 2.4 mg·L−1 IBA, 3% sucrose and 60 μmol·m−2·s−1 PPFD were found as suitable conditions for optimal induction of roots. In vitro regenerated Cattleya plantlets were successfully transferred to potting medium containing bark:perlite:peatmoss (1:1:1) and perlite:peatmoss (1:1), and 98.3 and 80.7% were survived respectively.

Fasciation in Crassula argentea : molecular identification of phytoplasmas and associated antioxidative capacity

The present study reports on phytoplasma induced fasciation in Crassula argintea (Crassulaceae). DNA was extracted from symptomless and fasciated tissues and amplified by nested PCR using universal primers P1/P7 followed by R16F2n/R16R2 produced amplicons of 1.2 Kb. The nucleotide sequence analyses of the amplicons indicated that fasciated plants were infected by phytoplasma. Phylogenetic analysis placed the Crassula fasciation phytoplasmas in 16SrII-D group. Histochemical staining for reactive oxygen species indicated that phytoplasma infected (PI) tissues possess significantly higher levels of hydrogen peroxide (H2O2) rather than superoxide (O2·-) as compared with symptomless tissues. PI tissues were also associated with a significant increase in antioxidant enzyme activities (catalase, peroxidase, polyphenol oxidase, and glutathione reductase) and electrolyte leakage as compared with symptomless tissues.

Thidiazuron-induced abnormalities in plant tissue cultures

Thidiazuron (TDZ) is a proven effective and potent synthetic plant growth regulator for organogenic, regeneration, and developmental pathways, including axillary and adventitious shoot proliferation, somatic embryogenesis, and in vitro flowering. TDZ has facilitated the establishment of in vitro cultures for several plant species, especially woody and recalcitrant plants, which has enabled their genetic transformation and improvement. Despite the effectiveness and advantages of using TDZ, several drawbacks are associated with its application in plant tissue culture. This review addresses the morphological, physiological, and cytogenetic abnormalities associated with the use of TDZ in vitro, and provides a summary of these abnormalities in several plant species.

African violet (Saintpaulia ionantha H. Wendl.): classical breeding and progress in the application of biotechnological techniques

ABSTRACT As a result of its domestication, breeding and subsequent commercialization, African violet (Saintpaulia ionantha H. Wendl.) has become the most famous and popular Saintpaulia species. There is interest in producing cultivars that have increased resistance to pests and low temperature, in the introduction of novel horticultural characteristics such as leaf shape, flower colour, size and form, and in improved productivity and enhanced flower duration in planta. In African violet, techniques such as the application of chemical mutagens (ethylmethanesulfonate, N-nitroso-N-methylurea), radiation (gamma (γ)-rays, X-rays, carbon ion beams) and colchicine have been successfully applied to induce mutants. Among these techniques, γ radiation and colchicine have been the most commonly applied mutagens. This review offers a short synthesis of the advances made in African violet breeding, including studies on mutation and somaclonal variation caused by physical and chemical factors, as well as transgenic strategies using Agrobacterium-mediated transformation and particle bombardment. In African violet, Agrobacterium-mediated transformation is affected by the Agrobacterium strain, selection marker, and cutting-induced wounding stress. Somaclonal variation, which arises in tissue cultures, can be problematic in maintaining true-to-type clonal material, but may be a useful tool for obtaining variation in flower colour. The only transgenic African violet plants generated to date with horticulturally useful traits are tolerant to boron (heavy metal) stress, or bear a glucanase-chitinase gene.

Cacti and succulent plant species as phytoplasma hosts: A review

The trade in ornamental cacti and succulent plants has been developed into an important industry, and it is accountable for the intercontinental commercialization of many new and old species. Several cacti are hosts for phytoplasmas and this could cause a severe threat to agriculture. Despite its deleterious effects, phytoplasma infection is considered useful, and as an added ornamental value in some cacti and succulent species. Diseases associated with phytoplasmas presence and their interaction with cacti and succulent species are reviewed.