Genetic and physiological characterization of seed dormancy regulation in common waterhemp [Amaranthus tuberculatus (Moq) Sauer]

Common waterhemp [Amaranthus tuberculatus (Moq.) Sauer.] is an annual plant native to the Midwest United States and is considered a troublesome weed species. The economic importance of common waterhemp is attributable to rapid population increases, the appearance of herbicide resistant biotypes, and the emergence phenology during the cropping season. Because seed dormancy levels can determine seedling emergence patterns, and the requirements necessary to remove common waterhemp seed dormancy and enhance germination are not well understood, we characterized the genetic and physiological regulation of common waterhemp seed dormancy and how seed dormancy is regulated by environmental signals such as moisture and temperature. The results indicated that seed dormancy levels in common waterhemp are highly influenced by temperature. Interactions between daily average temperatures and seed moisture reduce seed dormancy, and temperature fluctuation alleviates dormancy and triggers germination. The heritability of seed dormancy in common waterhemp is high. The heritability of genes involved in environmental signal sensing and seed dormancy regulation is more difficult to determine, but the existence and importance of these genes in seed dormancy was confirmed. In addition, the existence of intra-specific seed dormancy variation in common waterhemp was demonstrated. The evidence suggests that selection for complex seed dormancy regulatory mechanisms in common waterhemp is possible and might be one of the reasons why this weed has successfully thrived in the Midwest Region

Seed ecology of the geophyte Conopodium majus (Apiaceae), indicator species of ancient woodland understories and oligotrophic meadows

Funding Information European Union's Seventh Framework Programme. Grant Number: FP7/2007‐2013/ REA. Grant Number: 607785 Government of Asturias European Commission. Grant Numbers: ACA14‐19, ACB17‐19 Oxford BHF Centre for Research Excellence. Grant Number: RE/08/004Peer reviewedPublisher PD

Propagation of Coleonema album (Thunb.) Bartl. & J. C. Wendl. : a horticultural and medicinal plant.

Thesis (M.Sc.)-University of KwaZulu-Natal, Durban, 2012.Coleonema album is a South African green treasure, endemic to the Cape region and hard to find in other parts of the country. It is ranked among the most highly utilized medicinal plants at present. The plant extracts exhibit a wide range of pharmacological activities due to its bioactive compounds. Immunat, a tincture from this plant is marketed commercially. Medicinal plant gatherers are on the lookout for this plant due to its high demand and market price. Several natural product companies in South Africa are now exporting Coleonema album oil. Its showy beautiful white flowers make it a valuable ornamental plant. There is no accredited germination protocol available for this medicinal and ornamental plant till date. In this study, the chemical and environmental conditions required for optimum seed germination and seedling growth were studied. The effect of light, temperature shifts, cold and warm stratifications, smoke-water, butenolide, pH levels, plant growth regulators (kinetin, 6-benzyladenine, indole acetic acid and α-Naphthalene acetic acid), salt solutions (sodium chloride and ammonium nitrate) on seed germination were investigated. Seeds showed favourable response of germination at low temperatures (10 and 15 ºC). Seeds exposed to continuous darkness at low temperatures showed highest germination at 15 ºC. Temperature shift (from 20 ºC to 15 ºC) favoured seed germination. pH 6 is the most conducive pH level for Coleonema album seed germination (52.5%). Sodium chloride and ammonium nitrate solutions (pretreatment for 2 weeks) significantly improved germination at a 10-2 M concentration with 62.5 and 75% germination respectively. Coleonema album seeds exhibit a temperature-dependent physiological dormancy. Seed germination of this plant is quite erratic as seed germination started 21 days after incubation and lasted for over 90 days. Germination rate of the seeds is too slow to meet the local and international demand for this plant. Plant tissue culture techniques have been used as an alternative for mass cultivation of plants that are difficult to propagate from seeds. Therefore, an effective micropropagation protocol was developed as a measure to conserve this highly utilized medicinal plant. The effects of the cytokinins: BA, kinetin, TDZ and topolins on in vitro shoot formation of Coleonema album were investigated. Of all the cytokinins tested, 5 μM mT gave the highest number of shoots (14.50) per explant. Combination of 5 μM mT with various concentrations of IBA and NAA significantly increased shoot production. Shoots cultured on IBA supplemented medium produced roots. Root production from NAA cultures is unfavourable as most of the shoots developed callus at the base of the stem. The result of this study has shown that mT has potential as a highly active alternative to BA and other cytokinins for Coleonema album in vitro shoot production. Over 1,000,000 plantlets could be produced annually using the in vitro propagation protocol developed in this study. The results of this study will be useful as a guide for mass cultivation of this ornamental and medicinal plant. It will also provide an opportunity for propagation of Coleonema album in other parts of the country. By virtue of this, the pressure on the wild population of this species could be greatly reduced

Micropropagation and secondary metabolites of Sclerocarya birrea.

Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2009.Sclerocarya birrea (marula, Anacardiaceae) is a highly-valued indigenous tree in most parts of sub-Saharan Africa because of its medicinal and nutritional properties. The marula tree is adapted to the semi-arid conditions that characterise most parts of sub-Saharan Africa and renders them unsuitable for conventional crop agriculture. The unique nutritional properties of marula and its high tolerance to dry conditions provide opportunities for its development into a plantation crop. On the other hand, the demand for marula plant parts, mainly the bark and roots as medicinal remedies, poses a great threat to wild populations. In the long term, the growing demand of marula products in the food, pharmaceutical and cosmetic industries will not be sustainable from wild populations alone. Plant tissue culture technologies can be useful for in vitro manipulation and mass propagation of the plant in the process of domestication and conservation. The aims of the project were to determine the optimum conditions for seed germination, in vitro propagation and plant regeneration, and to evaluate the potential bioactivity of secondary metabolites from its renewable plant parts as an alternative option in the conservation of S. birrea. An ex vitro seed germination study indicated that after-ripening and cold stratification are critical factors. Cold stratification (5 °C) of marula nuts for 14 days improved germination (65%) as compared to non-stratified nuts (32%). Direct shoot organogenesis was achieved from leaf explants through the induction of nodular meristemoids on Murashige and Skoog (MS) (1962) medium and woody plant medium (WPM) supplemented with 6-benzyladenine (BA) in combination with naphthalene acetic acid (NAA), indole-3-butryric acid (IBA) and indole-3-acetic acid (IAA). Induction of nodular meristemoids from 86% of the leaf cultures was achieved on a MS medium with 4.0 ìM BA and 1.0 ìM NAA. High levels (78–100%) of induction were also achieved on WPM with different concentrations of BA (1.0–4.0 ìM) and IBA (1.0–4.0 ìM). The highest conversion of nodular meristemoids into shoots on MS initiation medium was only 22% for 4.0 ìM BA and 1.0 ìM NAA. This was improved to 62% when nodular clusters were cultured in MS liquid medium. Histological studies revealed high numbers of unipolar meristematic buds developing from globular nodules. These embryo-like structures have in the past been mistaken for true somatic embryos. The initiation of high numbers of nodular meristemoids per explant provides potential for automated large-scale clonal propagation in bioreactors, in vitro phytochemical production and the development of synthetic seed technology, similar to somatic embryogenesis. Plant regeneration through nodule culture has potential for application in mass micropropagation and plant breeding of S. birrea. Adventitious shoot and root induction are important phases in micropropagation. Plant growth regulators play an important role in these developmental processes, and the type and concentration used have major influences on the eventual organogenic pathway. Three auxins (IAA, IBA and NAA) and four aromatic cytokinins (6-benzyladenine, meta-topolin, meta-topolin riboside, and meta-methoxytopolin riboside) were evaluated for their potential to induce adventitious shoot and root formation in S. birrea shoots, hypocotyls and epicotyls. Among the evaluated cytokinins, the highest adventitious shoot induction (62%) was achieved on MS medium supplemented with meta-topolin (8.0 ìM). The lowest adventitious shoot induction (2.5%) was obtained on MS basal medium containing 2.0 ìM meta-methoxytopolin riboside. The highest adventitious shoot induction for hypocotyls was 55% on MS medium supplemented with 8.0 ìM meta-topolin. For the tested auxins, IBA induced adventitious rooting in 91% of shoots at a concentration of 4.0 ìM after 8 weeks in culture. However, the in vitro rooted plants only survived for two weeks when transferred ex vitro. A temperature of 25 °C and 16-h photoperiod were optimum for adventitious root induction. Stomatal density (number per mm2) on the abaxial leaf surfaces was higher for the 16-h photoperiod treatment (206.6 ± 15.28) compared to that for a 24-h photoperiod (134.6 ± 12.98). Normal mature stomata with kidney-shaped guard cells and an outer ledge over the stomatal pore were observed for in vitro plants growing under a 16-h photoperiod. Total phenolic content, proanthocyanidins, gallotannins, flavonoids, and antioxidant activities of S. birrea methanolic extracts were evaluated using in vitro bioassays. Methanolic extracts of the young stem bark and leaves contained high levels of these phytochemicals. Sclerocarya birrea young stem extracts contained the highest levels of total phenolics (14.15 ± 0.03 mg GAE g-1), flavonoids (1219.39 ± 16.62 ìg CE g-1) and gallotannins (246.12 ± 3.76 ìg GAE g-1). Sclerocarya birrea leaf extracts had the highest concentration of proanthocyanidins (1.25%). The EC50 values of the extracts in the DPPH free radical scavenging assay ranged from 5.028 to 6.921 ìg ml-1, compared to ascorbic acid (6.868 ìg ml-1). A dose-dependent linear curve was obtained for all extracts in the ferric-reducing power assay. All the extracts exhibited high antioxidant activity comparable to butylated hydroxytoluene based on the rate of â-carotene bleaching (89.6 to 93.9%). Sclerocarya birrea provides a source of secondary metabolites which have potent antioxidant properties and may be beneficial to the health of consumers. Sclerocarya birrea young stem and leaf ethanolic extracts exhibited high bioactivity (MIC < 1.0 mg ml-1) against both Gram-positive (Bacillus subtilis and Staphylococcus aureus) and Gram-negative (Escherichia coli and Klebsiella pneumoniae) bacteria. The highest activity (MIC = 0.098 mg ml-1 and total activity = 1609.1 ml g-1) was recorded for young stem extracts against B. subtilis. The highest activity (MIC = 1.56 mg ml-1 and MFC = 1.56 mg ml-1) in the antifungal assay against Candida albicans was observed for young stem ethanolic extracts. Sclerocarya birrea extracts had moderate acetylcholinesterase (AChE) inhibition activity. The dichloromethane (DCM) and methanol (MeOH) fractions exhibited dose-dependent acetylcholinesterase inhibitory activity. The highest AChE inhibitory activities were from leaves (DCM fraction, IC50 = 0.1053 mg ml-1) and young stems (MeOH fraction, IC50 = 0.478 mg ml-1). High inhibitory activity against cyclooxygenase (COX-1 and COX-2) enzymes was observed. All extracts and fractions showed high COX-1 enzyme inhibition (90.7-100%). Petroleum ether (PE) and dichloromethane fractions also exhibited high inhibition against COX-2 enzyme (77.7-92.6%). The pharmacological activities observed suggest that S. birrea renewable plant parts (leaves and young stems) provide a substantial source of medicinal secondary metabolites. Based on these results, plant part substitution can be a practical conservation strategy for this species

Plant Physiology, Development and Metabolism

Water is one of the most important constituents of life. Chemically, water is the hydride of oxygen. Oxygen, being more electronegative, exerts a strong attractive pull on its electrons. This unequal attraction results in small positive charge on twohydrogenmoleculesandasmallnegativechargeontheoxygenmolecule.The two lone pairs of electrons of the oxygen molecule result in bending of water molecule. The partial charges on oxygen and hydrogen molecules result in high electric dipole moment and polarity of water molecule

Interspecific Hybridization in Plant Biology

Many crop gene pools are derived from a small number of founders. As a consequence of long histories of strong directional selection, crop gene pools have narrow genetic diversity available to provide inherent solutions to changing needs or challenges. Notoriously, plants can mate across taxonomically-determined species boundaries, and interspecific hybridization is widely used in plant genetics research. Interspecific hybridizations have conferred practical improvements to crops, some of which are unexpected based on the phenotypes of the parents. Genomics has provided insights into the fundamental consequences of interspecific hybridization for plant biology. Additionally, genomics has allowed the development of molecular tools for dissecting the genetic control of phenotypic variation in interspecific hybrid populations and manipulating interspecific introgressions in crop improvement. This Research Topic aims to publish peer-reviewed research to interspecific hybridization and its consequences, both fundamental and applied. While such work is prominent in plants, consideration will also be given to salient work in other taxa. A key threshold for publication will be the extent to which findings are of cross-cutting interest and importance, i.e. not only to those working on the target taxon but to a wide range of biological scientists.Peer reviewe

Plant Diseases

Plant pathogens, the causal agent of infectious plant diseases, influence our lives more than just as an economic impact through yield lost. The study of plant pathogens has given rise to the development of new sciences, new technologies for plant breeding, and the agrochemical industry for pesticide developments. Yet, all our actions and efforts to suppress or eradicate them constantly pressures these various organisms to evolve and adapt for survival. Therefore today, when facing climate changes, accelerated transport of plants and plant products, and world population growth, we have to ask quo vadis phytopathology. Like Alice in Wonderland “If we wish to go anywhere we must run twice as fast as that” so we need to constantly broaden our knowledge. However, today’s literature abounds with knowledge about plant pathogens. Hence, this book intends to present to the reader all the latest material and knowledge about plant pathogens, changes or refinements in plant disease epidemiology, and new approaches and materials used for plant pathogen control. Hopefully, this book will be of interest to those working within the field and looking for an up-to-date introduction. We hope it also interests students and thereby, will influence the future development of phytopathology and our better coexistence with plant pathogens

Association of agronomic and forage quality traits in red clover (Trifolium pratense L.)

Red clover (Trifolium pretense L.) is a source of highly nutritional voluminous forage for livestock feed. The objectives of this investigation were to: I) annotate associations of agronomic and forage quality traits of red clover accessions; II) group accessions in relation to analyzed traits. The plant material used included 46 cultivars and local populations, which originated from 17 countries, representing part of the red clover collection from the Institute of Field and Vegetable Crops in Novi Sad, Serbia. The field trial was sown during two growing seasons in Novi Sad. The agronomic traits (plant height-PH, internodes number per stem-IN, green mass yield-GMY, dry matter yield-DMY) were evaluated from the second cut in the nursery of the second year of life. Forage quality traits analyzed were content of neutral detergent fibers (NDF), acid detergent fiber (ADF), and crude protein (CP). In regard to very strong associations of PH, GMY and DMY, and to moderately strong associations of PH and IN, it could be anticipated that the indirect selection for higher plants with higher IN can lead to higher GMY and DMY. The breeding of red clover for NDF and ADF and elevated CP might be successful, but can reduce herbage yield (due to very weak positive and negative associations with GMY and DMY). The accessions were grouped to the six clusters which can facilitate selection and breeding for different agronomic and quality objectives