Hamidou F. Sakhanokho

Chemical Composition, Antifungal and Insecticidal Activities of Hedychium Essential Oils

The antimicrobial properties of essential oils have been documented, and their use as “biocides” is gaining popularity. The aims of this study were to analyze the chemical composition and assess the biological activities of Hedychium essential oils. Oils from 19 Hedychium species and cultivars were analyzed by gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS) techniques. The antifungal and insecticidal activities of these oils were tested against Colletotrichum acutatum, C. fragariae, and C. gloeosporioides, and three insects, the azalea lace bug (Stephanitis pyrioides), the yellow fever mosquito (Aedes aegypti), and the red imported fire ant (Solenopsis invicta). Hedychium oils were rich in monoterpenes and sesquiterpenes, especially 1,8-cineole (0.1%–42%), linalool (<0.1%–56%), α-pinene (3%–17%), β-pinene (4%–31%), and (E)-nerolidol (0.1%–20%). Hedychium oils had no antifungal effect on C. gloeosporioides, C. fragariae, and C. acutatum, but most Hedychium oils effectively killed azalea lace bugs. The oils also show promise as an adult mosquito repellent, but they would make rather poor larvicides or adulticides for mosquito control. Hedychium oils acted either as a fire ant repellent or attractant, depending on plant genotype and oil concentration.

First Report of Plant Regeneration via Somatic Embryogenesis from Shoot Apex-Derived Callus of Hedychium muluense R.M. Smith

ABSTRACT The genus Hedychium consists of about 50 species, with increasing popularity as ornamentals and potential as medicinal crop plants, but there are no reports on somatic embryogenic regeneration of any member of this genus. The objective of this investigation was to establish an in vitro regeneration system based on somatic embryogenesis for Hedychium muluense R.M. Smith using shoot apex-derived callus. Callus was induced and proliferated on a modified Murashige and Skoog (MS) medium (CIPM) supplemented with 9.05 μM 2–4, D, and 4.6 μM kinetin. Friable callus developed into somatic embryos upon transfer to liquid medium (MS basal salts and Gamborgs vitamins) that was supplemented with 0.6 μM thidiazuron (TDZ) and 8.9 μM 6-benzylaminopurine (BA) and shaken for four weeks. The cultures were then transferred to three Hedychium embryo-development media (HEDM) of varying strengths: HEDM, 1/2 HEDM, and 1/4 HEDM. All three media contained both 0.6 μM TDZ and 8.9 μM BA. Somatic embryo production was higher in full strength HEDM, which produced an average of 103 somatic embryos/explant, half of which could be converted into shoots within a month. Regenerated shoots were readily rooted on a medium supplemented with 0.6 μM 3-indoleacetic acid (IAA) and acclimatized before transfer to the greenhouse.

Alginate Encapsulation of Begonia Microshoots for Short-Term Storage and Distribution

Synthetic seeds were formed from shoot tips of two in vitro grown Begonia cultivars using 3% sodium alginate in Murashige and Skoog medium (MS) salt solution as the gel matrix and 100 mM calcium chloride for complexation. Synthetic seed formation was achieved by releasing the sodium alginate/explant combination into 100 mM calcium chloride (CaCl2 ·H2O) solution for 30 or 45 min. Both control and encapsulated shoots were transferred into sterile Petri dishes and stored at 4°C or 22°C for 0, 2, 4, 6, or 8 weeks. Conversion of synthetic seeds into plantlets for both storage environments was assessed in MS medium or peat-based substrate. No significant difference was found between the 30 and 45 min CaCl2 ·H2O treatments or the two cultivars. Encapsulation of explants improved survival rate over time irrespective of the medium type or storage environment. Survival rates of 88, 53, 28, and 11% for encapsulated microshoots versus 73, 13, 0, and 0% for control explants were achieved in microshoots stored for 2, 4, 6, and 8 weeks, respectively. The best results were obtained when synthetic seeds were stored at 4°C and germinated on MS medium. Regenerated plantlets were successfully established in potting soil.

Antifungal Activities of Hedychium Essential Oils and Plant Extracts Against Mycotoxigenic Fungi

Plant-derived antifungal compounds are preferred to chemicals to reduce the risk of toxic effects on humans, livestock, and the environment. Essential oil extracted from rhizomes and plant extracts of ornamental ginger lily (Hedychium spp.) were evaluated for their antifungal activity against two fungi, Aspergillus flavus and Fusarium verticillioides, that produce two major classes of mycotoxins, aflatoxin, and fumonisin, respectively, on several crops. Essential oil or leaf extracts from several Hedychium species and varieties totally inhibited the growth of pre-germinated spores of A. flavus and F. verticillioides. Control of these two fungi by aqueous extracts of rhizome was not effective, although a reduced number of colonies was observed. In view of these results, essential oils or crude leaf extracts from Hedychium spp. need to be considered for the control of mycotoxin-producing fungi under storage conditions.

Cotton Regeneration In Vitro

Over the years, plant breeders have improved cotton via conventional breeding methods, but these methods are time-consuming. To complement classical breeding and, at times, reduce the time necessary for new cultivar development, breeders have turned to in vitro plant transformation or genetic engineering, relying mostly on two major approaches, Agrobacterium-mediated and particle bombardment transformation techniques. Since its adoption in the 1990s, transgenic technology continues to have a tremendous impact on cotton production not only in the United States but also worldwide. Currently, genetically modified cottons, in particular insect and herbicide tolerant cotton, account for over 90 and 80 % of cultivated cotton acreage in the United States and worldwide, respectively. However, efforts in the development of transgenic cotton are hampered by the recalcitrance of most cotton cultivars, particularly the elite cultivars, to regenerate via tissue culture, a step very often necessary for the transformation process. In vitro regeneration of cotton, in particular regeneration via somatic embryogenesis, is highly genotype dependent. In addition, other factors including explant type, composition and type of media (liquid vs. solid) as well as environmental conditions surrounding the cultures affect the in vitro regeneration of cotton. In this chapter, the current status of different regeneration methods and the factors limiting or enhancing these methods are discussed.

Morphological and Cytomolecular Assessment of Intraspecific Variability in Scarlet Eggplant (Solanum aethiopicum L.)

Solanum aethiopicum L. is native to sub-Saharan Africa but is now found in many parts of the world. It is used for food, medicinal, and ornamental purposes. It has also been used as a rootstock for tomato and common eggplant because of its resistance to certain pathogens. However, very little is known about its genetics, so the purpose of this work was to assess intraspecific variability in S. aethiopicum via morphological and cytomolecular characterization of 12 scarlet eggplant accessions. Cluster analysis was used for grouping the accessions using means of 27 variables. Four separate groups were found, with two groups each consisting of five accessions and two other groups each consisting of only one accession. Variability was high with flower- and fruit-associated descriptors among the accessions. Monoploid genome sizes (Cx-value), average chromosome sizes (C/n-value), and GC content were determined. Haploid genome size of S. aethiopicum ranged from 1.312 pg/1C to 1.538 pg/1C., which is close to the genome size (1.2 pg/1C) of the common eggplant. Only PI 420226 (1.538 pg/1C) was significantly different from the rest, giving credence to the theory that PI 420226 is actually a S. macrocarpon accession. GC content of S. aethiopicum accessions was about 40%. We used 18S-28S rDNA and 5S rDNA probes to study the distribution and physical position of these ribosomal genes in S. aethiopicum. These results help to better understand intraspecific variability in S. aethiopicum and can be important for the breeding and selection of this crop.

Diversity in nuclear DNA content and ploidy level of Hedychium species and hybrids

ABSTRACT Hedychiums are multipurpose plants cultivated as ornamentals because of their multicolor and showy and scented flowers and as medicinal plants because of their essential oils that have been found to possess antimicrobial and insecticidal properties. There is often taxonomic and botanical confusion about Hedychium species and cultivars because of the apparent existence of more than one cytotype within several Hedychium species, most likely because of the ease with which these species hybridize. Nuclear DNA content (2C-DNA) was determined for the first time in 23 Hedychium species and hybrids. The 2C-values ranged from 1.70 pg to 3.98 pg. We also determined the chromosome number of one species, Hedychium stenopetalum, which was found to be diploid (2n = 2x = 34), supporting the widely held view that the basic chromosome number in Hedychium is x = 17, and the existence of different cytotypes is most probably attributable to natural hybridization. Our results should be helpful not only in clarifying the botanical and taxonomic confusion in Hedychium but also in paving the way for a sound breeding program for this increasingly important ornamental ginger.