Vernonia Species Research Articles

Pharmacognostic Study and Phytochemical Profilling of Dichloromethane Extracts of the Leaf and Stem of Vernonia conferta Benth and Vernonia colorata Drake Asteraceae

Aims: The study determines various taxonomic, pharmacognostic and phytochemical standards helpful to ensure the identity, purity, safety and efficacy of Vernonia colorata and Vernonia conferta. Study Design: To study these two species of Vernonia for their epidermal cell shapes, stomatal types and distribution, trichome types, chemomicroscopic and fluorescence characters, flow properties, ash values, extractive solvents and phytoconstituents of dichlormethane fractions using GC-MS. Place and Duration: This study was conducted at the Department of Pharmacognosy and Natural Medicine, Faculty of Pharmacy, University of Uyo, Uyo from June 2023 to December 2023. Methodology: The pharmacognostic characterization was determined following the guidelines given by the World Health Organization (WHO). Parameters determined included microscopy, powder microscopy, chemomicroscopy, micromeritic properties, ash values, extractive values, fluorescence analysis while phytochemical analysis was done using Gas Chromatography coupled to Mass Spectrometer. Results: Epidermal cell shapes were both irregular with undulate and sinuous anticlinal wall pattern for both V. colorata and C. conferta respectively. Stomatal distribution was hypostomatic with paracytic stomata on the abaxial surface for C. conferta while amphistomatic with anomocytic stomata in V. colorata. Stomatal index was highest in V. conferta with 27.31% and least in V. colorata 21.52%. Unicellular trichomes were observed in V. colorata and V. conferta epidermal surfaces. The chemomicroscopic study revealed the presence of lignin, starch, cellulose, oils, calcium oxalate crystals, mucilage and protein for both leaf and stem respectively. The fluorescence characteristics showed the presence of different colours supporting the presence of various phytoconstituents for both leaf and stem. The quantitative epidermal studies, chemomicroscopic and fluorescence characteristics revealed characteristic features for the drug. The flow properties for both leaf and stem were poor. The total ash values for both leaf and stem ranges between (2.40 – 9.30 and 10.60 – 11.06), acid-insoluble ash values were low, moisture contents were between 8 - 14%w/w, water and methanol extracted more constituents. In total, 12 chemical constituents each were recorded for the leaves of V. colorata and V. conferta, respectively, while 10 and 12 were also recorded for the dichloromethane stem extracts of V. colorata and V. conferta, respectively. Conclusion: This study is useful in pharmacognostic standardization of Vernonia colorata and Vernonia conferta.

COMPARATIVE WOOD ANATOMY OF FOUR Vernonia delile SPECIES (ASTERACEAE) IN SOUTHWESTERN NIGERIA.

Wood anatomy of four Vernonia Delile species in Southwestern States of Nigeria was investigated with a view to identifying the anatomical features of the genus that could be used to delimit the taxa. Plant samples were collected from Oyo, Ekiti, Osun and Ondo States. Transverse, tangential and radial longitudinal sections were made from the wood of the species of Vernonia using Reichert sliding microtome at 10μm thickness. The woods were also macerated with Schultze's uid to separate the tissues and cells. The macerates and cut sections were stained with Safranine O reagent to reveal the differences in tissue arrangements, shapes and cell inclusions. The four species showed common anatomical features: pore shape at transverse plane are oval, round, rectangular circular to cylindrical, simple pitting of vessel elements and presence of - uniseriate, biseriate and multiseriate rays. The wood characteristics that can be used to distinguish the taxa are absent and presence of : tylose, bre length and percentage of solitary vessel, axial parenchyma type and its absence. These features conferred signicant taxonomic difference in the species and members were categorized into three major groups. These ndings serve as baseline for further research such as molecular studies.

Improved beekeeping practices, honey bee flora potential and flowering calendar in South Ethiopia.

In Ethiopia, improved hive technology dissemination was started before five-decades. However, the adoption of improved beekeeping technology is still very low. This study was conducted with the main objectives to evaluating improved beekeeping adoption level and honey yields of different hives and identification of major honey bee plants and flora calendar in the Gedeo zone, South Ethiopia. Three districts were selected purposively based on beekeeping potential and the number of improved hives own by beekeepers. The data was collected from 180 respondents using cross-sectional survey. The data was analyzed by using descriptive statistics such as mean, frequency and percentage and ANOVA. The result shown that the compositions of disseminated hives in the entire sampled respondents were 286, 476, 121 and 1494 Zander hive, Kenyan top bar hive (KTBH), Mud/Ethio-Ribrab hive (ERH) and Traditional hives respectively. Traditional beekeeping was the dominant system with 63% and intermediate followed by 25%, while modern beekeeping was only 12%. Based on overall mean honey yield, there was no significant difference (P = 0.244) between Zander and KTBH. However, the average honey yield of these improved hives were significantly (P<0.05) higher than Mud/ERH and Traditional hives. Gedeo zone had rich floral resource and diverse floral calendar. Hygenia abyssinica, Bidens ghedoensis, Erythrinia abyssinica, Eucalyptus species, Cordia africana, Coffee arabica, Vernonia species, Susbania susban and Persea americana were major honey bee flora in Gedeo zone. February-March was major honey harvesting season while May-July and October-December respectively were minor honey harvesting periods. Nevertheless, the majority of beekeepers have been practicing honey harvesting once a year from all hives due to lack of awareness and practical skills. Therefore, we recommend that the local government should focus on educating beekeepers to enable them utilizing exhaustively the opportunities of multi-floral season and improved hive technology to maximize honey yield in the area.

Genus Vernonia - Mini Review

Vernonia is one of the largest taxa under Asteraceae family with approximately 1000 species. This taxon is commonly distributed in South America, Africa, Southeast Asia, and North America. Vernonia speciesare widely used as leafy vegetables especially in some of the African countries. Some species of Vernonia has been used in traditional medicines to treat variety of ailments. In many countries, including India this plan has turned up into obnoxious weed. Species of Vernonia consists of phytochemicals such as fats, proteins, fats, amino acids, minerals, fibres, vitamins, and carbohydrates. Keywords: Genus Vernonia, Asteraceae, Morphology and ethnomedical applications.

First Report of Powdery Mildew Caused by Podosphaera xanthii on Vernonia cinerea in China.

Vernonia cinerea (L.)Less. is an annual herbaceous plant of the Asteraceae family, which is widely distributed throughout Southeast Asia, India, and the tropical and subtropical regions of China. This herb is known to contain various bioactive compounds and is commonly used in traditional system of medicine in China and India (Singh et al. 2021). During the spring of 2022 and 2023, powdery mildew symptoms were observed on 70% of V. cinerea plants on the Hainan Medical University campus (19° 58' 53″ N; 110° 19' 47″ E) in Haikou, Hainan Province, China. Powdery mildew colonies covered the leaf surfaces and stems of affected plants, causing discoloration and defoliation. Mycelia were superficial and hyphal appressoria were nipple-shaped. Conidiophores (n =30) were unbranched, cylindrical, 104 to 188 × 11 to 15 µm, and produced three to five immature conidia in chains with a crenate outline. Foot cells (n =30) were cylindrical, straight or sometimes curved at the base, and 32 to 57 µm long. Conidia (n =100) were ellipsoid-ovoid to doliiform, 19 to 45 ×16 to 26 m (length/width ratio = 1.2 to 2.4), with well-developed fibrosin bodies, and produced germ tubes from the lateral position. Based on these morphological characteristics, the pathogen was provisionally identified as Podosphaera xanthii (Braun and Cook 2012). The teleomorph was not observed. A specimen was deposited in the Hainan Medical University Plant Pathology Herbarium as HMVC-22. To confirm the genus identification and ascertain a putative species, genomic DNA was extracted from mycelium, conidiophores, and conidia using a fungal DNA kit (Omega Bio-Tek, USA). The rDNA internal transcribed spacer (ITS) region was amplified with primers ITS1/ITS4 (White et al. 1990) and sequenced directly. The resulting 577-bp sequence was deposited in GenBank (accession no. OP765400). A BLASTn search in GenBank of this sequence showed 100% similarity with the ITS sequences of P. xanthii isolates from China (MT260063, MT739423 and MT131253), Thailand (LC270780), and Vietnam (KM260731). Additionally, the 28S rDNA region was amplified using the primer pairs NL1 and NL4 (O´Donnell 1993; accession no. OP765401). This region shared 100% similarity with P. xanthii isolates (LC371333, LC270780, and AB936277) as well. Powdery mildew from Hainan sample belonged to the P. xanthii group with strong bootstrap values support 99% in maximum likelihood phylogenetic tree based on ITS and 28S gene sequences. To confirm pathogenicity, five healthy potted plants of V. cinerea were inoculated by gently pressing a powdery mildew-infected leaf onto 15 young leaves. Five non-inoculated plants served as controls. All plants were maintained in a greenhouse at 24 to 30°C, 70% relative humidity, with a 16-h photoperiod. After 7 days, inoculated leaves showed powdery mildew symptoms whereas no symptoms were observed on control plants. The fungal colonies observed on inoculated plants were morphologically identical to those found on the originally infected leaves collected from Hainan Province. Based on the morphological characteristics and molecular identification, the fungus was identified as P. xanthii. In different countries and regions, Erysiphe cichoracearum has been previously reported on some Vernonia species, including V. Galamensis from southern parts of Ethiopia (Hundesa and Mekonnen 2017). To our knowledge, this is the first record of P. xanthii infecting V. cinerea in China. We are concerned that the pathogen could become a threat to the widespread planting of V. cinerea in the future.

Vickianthus, a new genus of the Vernonieae (Compositae) from Mexico

The morphologically diverse and globally distributed tribe Vernonieae (Compositae) has had a long taxonomic history whereby the majority of its taxa ended up being put into its “core” genus, Vernonia Schreb. Recent phylogenetic studies using DNA sequence data are only now beginning to tease apart this complicated “evil tribe” and provide a better understanding of the underlying morphological relationships within. With strong support from a recent molecular phylogenetic study of the Vernonieae across its entire geographical range, ten Mexican species of Vernonia and Vernonanthura are examined in this paper and placed in a new genus, Vickianthus.

Genus Vernonia (Asteraceae): A Promising Source of Antitumor Agents with Pharmacological Potentials

Antitumor research leads to the development of new molecules that act specifically in tumor cells by blocking or inhibiting their molecular targets. New therapeutic approaches for the screening of bioactive compounds present in medicinal plants have received increasing attention due to their chemopreventive and chemotherapeutic properties. In ethnomedicine, plants of the genus Vernonia (Asteraceae) are widely used and some have shown several and interesting biological activities, including anticancer. This present study aimed to document experimental evidence supporting the claimed ethnomedical uses of Vernonia species for the treatment of various types of cancer and also to confirm the anticancer potential of these plants. The compounds isolated from aqueous and alcoholic extracts, as well as fractions from different parts of Vernonia plants have acted as potential anticancer agents that inhibited the proliferation of various types of human cancer cell lines, including cervical cancer cells, melanoma cells, promyelocytic leucemia cells, breast adenocarcinoma cells, ovarian cancer, liver cancer cell, and human lung cancer cells. Studies have correlated the antitumor activity of Vernonia plants by inducing apoptosis and modulating mitochondrial signaling pathways controlled by NF-κB, Bcl-2 and p53, as well as inducing DNA damage and arresting the cell cycle at the S-phase checkpoint by oxidative stress. In conclusion, Vernonia species act as a promising source for drug development. However, further studies are needed to explore the exact mechanism of action, pharmacokinetics, chronic toxicological studies, safe dose consumption, and possible interactions with other herbs.

Assessment of Major Honey Bee Forage Resources and Floral Calendar Establishment in Selected Districts of Arsi Zone, Oromia Region State, Ethiopia

The study was conducted from 2015 to 2017 G.C. with the objective of identifying and documenting honey bee forage plant resource, establishing flowering calendar and recommending the necessary seasonal colony management practices in selected districts of Arsi zone. Semi-structured questionnaire tool was used to collect data. Ninety beekeepers were selected and involved in data collection. Traditional, transitional and modern bee hives were used for honey production. The overall mean of colony owned per household in the current study areas was found to be 5.2 + 5.2. Honey production was conducted during two seasons namely: major and minor seasons. The mean of honey yield per traditional, transitional and modern hive was 10.8 + 5.9kg, 19.8 + 17.3kg and 33.2 + 48.9kg, respectively. 61.1% of the respondents harvest honey two times a year, whereas 34.5% of them harvest honey once a year and 4.4% of respondents three times a year. Honeybee was found to be in critical shortage of forage during months ranging from December to August. A total of 98 plant floras including trees, shrubs, herbs, cultivated crops and animal feeds and grasses were identified in the current study areas. G uizotia scabra, equiliptus globules and vernonia species were the most frequently identified plant species . The knowledge in the identification of honey bee flora and their flowering time has therefore paramount importance in assisting beekeepers to establish appropriate colony management calendar and honey flow season. Further detail studies focusing on bee flora should be conducted and awareness creation of experts and farmers on seasonal management of beehives through training is required. Keywords: honey bee, bee flora, flowering time, Arsi, Ethiopia DOI: 10.7176/JRDM/83-02 Publication date: March 31 st 2022

Leaf epidermal and petiole anatomical features as taxonomic characters in some Vernonia species in Nigeria

Foliar and petiole micro-morphological characteristics of some members of the genus Vernonia namely; Vernonia amygdalina Del. (bitter variety), Vernonia amygdalina Del. (non-bitter variety), Vernonia cinerea (L) Less., Vernonia galamensis (Cass.) Less., and Vernonia adoensis Sch. Bip. in Jos, Nigeria was investigated to provide additional micro-morphological characters to support existing taxonomic information regarding the species. Epidermal peels of fresh leaves were made and transverse sections of petioles were cut using a rotary microtome. Staining was done using Safranin and slides observed using a light microscope. Quantitative characters were measured and subjected to Duncan Multiple Range Test. Stomatal distribution was amphistomatic except for V. galamensis and V. cinerea with hypostomatic distribution; stomata type was mostly anomocytic except V. galamensis with paracytic stomata. Stomata index varied among taxa with V. adoensis and V. amygdalina (bitter variety) having the highest (10.84 %) and lowest (0.67%) respectively. Anticlinal cell wall patterns were straight to slightly undulate while wavy anticlinal cell wall pattern was diagnostic to V. cinerea. Trichome types observed were glandular and multicellular uniseriate with highest and lowest trichome indices recorded in V. adoensis (2.80%) and V. galamensis (0.02%) respectively. Petiole outline was convex to concave, epidermis was uniseriate, trichome multicellular uniseriate and vascular bundles bicollateral. Variations observed in the stomatal complex, epidermal cell complex, petiole outline, petiole vasculature type, trichome and stomata indices could be employed for species identification and delimitation.

Identification, characterization and evaluation of honeybee floras in Kafa, Sheka and Benchi Maji Zones of Southern Nations Nationalities and Peoples Region (SNNPR), Ethiopia

The study was aimed with identifying and characterizing honeybee floras and their flowering seasons in south western parts of the country. Relevant data were collected through conducting questionnaire survey, focus group discussions, field observations and lab analysis of pollen and honey samples. In addition, seasonal performance of colonies in terms of brood area, adult population, pollen and nectar stores were evaluated. The obtained data were analyzed using SPSS-ver.20 and MsExcels. Accordingly, a total of 200floral species categorized under 77families identified. Of which, 26(13%) grouped under 16 families characterized as major bee floras. Seasons, January to February, July to August were considered as Dearth periods; March, September to October were brooding seasons, April, November to December were major nectar flow seasons. March to April and November to December were major honey flow seasons being the first for high land and mid land areas and the later for lowland areas whose major botanical origin was Schefflera abyssinica and Guizetia scabra respectively. However, in some areas with better forest covers, Manilkara butij become a major honey source plant. Whereas, January, June to July, March (in low lands) were considered as minor/mini harvesting seasons whose major botanical origin was Vernonia species, Croton macrostachyus and Combritum species respectively. It was noted that there was a significant correlation among brood area, adult population, pollen store and nectar stores at p&lt;0.01.

Secondary metabolite contents and antimicrobial activity of leaf extracts reveal genetic variability of Vernonia amygdalina and Vernonia calvoana morphotypes.

Vernonia species (Asteraceae) are indigenous medicinal and food leaf vegetables commonly consumed in some African countries like Cameroon where they constitute a staple dish called "ndolé." Previous studies have demonstrated the nutritional importance of Vernonia, but there is little knowledge of their agronomic value and genetic potentials. Wide genetic variability in the genus has been established earlier through the study of its pollen. However, to the best of our understanding, no such study has been undertaken on the genetic variability of Vernonia with respect to its secondary metabolites. This study was therefore aimed at evaluating the genetic variability of Vernonia amygdalina (VAA and VALF) and V. calvoana (VCAB, VCAV, VCSB, and VCSV) morphotypes in 2016 based on secondary metabolite content and antimicrobial properties. This involved phytochemical analysis by HPLC/MS for the detection of alkaloids, flavonoids, phenols, and tannins in leaves from each of the six genotypes. Results showed that all tested genotypes are rich in phenols (18 analyzed), flavonoids, and tannins with, VAA richer in phenols (206.1 ± 3.12µg/g of dry extract), followed by VCAV (197.9 ± 18.03µg/g). The lowest level of flavonoid was found in VCSV (81.6 ± 7.21µg/g), while the highest was from VCAB (132.8 ± 31.5µg/g). VCSV (56.3 ± 4.08µg/g) had the lowest level of tannins, while VCAB (97.8 ± 23.8µg/g) had the highest levels. Assessment of antimicrobial activity of leaf extracts from the six genotypes was done by culture on Mueller Hinton (MH) agar and MH broth agar for bacteria and in Sabouraud dextrose agar and Sabouraud dextrose broth media for fungi, respectively. All morphotypes exhibited inhibitory activity on bacteria except VAA, with isoquercetin characteristic of VCSV. Chemotaxonomic analyses of Vernonia morphotypes highlighted the genetic diversity within species and variability of antimicrobial properties of ethanolic leaf extracts among morphotypes. These results provide baseline data in the valuation of genetic resources and the establishment of improvement programs.

English

This study aims to screen possible antioxidant potentials of methanol extract and polar fractions of Vernonia calvoana leaves and its phytochemical constituents since the leaves are used ethno medically in managing ailments like wounds, blood pressure, inflammation, arthritis, and bone diseases. Dried leaves (900 g) were ground and de-fatted with n-hexane. The dry marc was extracted using 80% methanol and water. Filtrate was concentrated using rotary evaporator at 40°C. Acute toxicity study and phytochemical analysis were performed with crude extract. Fractionation of crude extract using gradient concentrations of methanol and distilled water yielded 4 fractions - F1, F2, F3 and F4. Fractions with the crude were used for in vitro antioxidant studies. From the results, crude extract showed no signs of toxicity in mice at 2000 mg/kg orally. Phytochemical screening showed presence of alkaloids, flavonoids, tannins, phenols, steroids, saponins, terpenes, arthroquinones, carbohydrates and glycosides. The highest percentage antioxidant activity observed with crude extract was 72.37 at 500 µg/ml in DPPH spectrophotometric assay. DPPH results showed percentage antioxidant activity of 81.4% at 500 µg/ml of F1 and 67.73% at 500 µg/ml of F2. The FRAP values of the crude extract, F1, F2, F3 and F4 at 500 µg/ml were 1.957, 2.234, 1.731, 1.245 and 1.025 µM respectively. These results showed that the activities of methanol extract of leaves of V. calvoana may be dependent on the concentration of the extracting solvent. Vernonia species are known to contain abundant saponins and flavonoids which are polar compounds and readily soluble in methanol. This may explain the above observed antioxidant activities and thus, the use of the leaves in different traditional curative therapies in Southern Nigeria. Key words: Vernonia calvoana, leaves, antioxidants, crude extract, phytochemicals.

Anatomical Studies of the Midrib, Petiole and Epidermal Strip of Some Vernonia Species, from Nigeria

Anatomical Studies of the Midrib, Petiole and Epidermal Strip of Some Vernonia Species, from Nigeria

Leaf Epidermal Features in 14 Species of Vernonia.

Leaf Epidermal Features in 14 Species of Vernonia.

VernoniasubgenusAustrovernonia, a new subgenus from South America (Compositae, Vernonieae, Vernoniinae).

Vernoniaincana Less. and V.echioides Less. are two semi-aquatic species from southern South American that are referred to as “the semi-aquatic Vernonia of South America” and they have been, until now, retained as members of Vernonia mostly because each had some unusual characters that made them hard to place. Based on an ongoing molecular study, we can now say that V.incana is the sister taxon to all true Vernonia and can therefore be responsibly left in Vernonia but, because of its morphological and geographic differences, it is now assigned to its own subgenus: Vernonia subg. Austrovernonia. Vernoniaechioides is not closely related to V.incana and is now part of a separate investigation. This placement of V.incana as sister to the true Vernonia species brings up the possibility of a South American root for the Vernonia clade and perhaps indicates a propensity in the lineage for growing in or near water. The species V.incana is lectotypified.

Abstract 4394: Novel edible medicinal plant induced cytotoxic and apoptotic effects on ovarian cancer cells

Abstract Ovarian cancer (OC) is the leading cause of death in gynecologic cancer and the fifth most common form of cancer diagnosed among women. Caucasians have a higher incidence and mortality rate compared to African-Americans. The low survival rate of ovarian cancer among patients is caused by the fact that ovary organs are located inside the pelvic region in the female reproductive system; many cases are diagnosed in advanced stage, when cancer has already metastasized beyond the ovaries. Consequently, there is an urgent need to prevent ovarian cancer at the early stage and provide effective treatment. Herbal medicine with lesser or no side effect is currently considered as an alternative cancer treatment because it possesses many bioactive compounds essential to destroy cancer cells. A preliminary study in our laboratory demonstrates that extracts of Vernonia species have antitumor activities against cancer cells. Therefore, our overall goal in this study was to test the therapeutic mechanisms of a Vernonia species (an edible medical plant) in the treatment of ovarian cancer. To reach our goal, we tested the cytototic and apoptotic effects of the Vernonia species on OVCAR-3 cells. Data generated from the trypan blue test and MTT assay demonstrated that extracts of Vernonia species exhibited significant growth-inhibitory effects on OVCAR-3 cells. Oxidative stress biomarkers showed slight decrease in the production of malondialdehyde (MDA) levels and an increase in catalase activity and glutathione peroxidase in treated cells compared to the control group. Further experiments, including cell morphology and apoptosis analysis, showed that VA caused growth-inhibitory effects on OVCAR-3 cells through cell cycle arrest at the Go/G1 checkpoint and activation of caspase-3 activity leading to apoptosis. Collectively, findings from this study provide convincing scientific evidence that the Vernonia species tested here may represent a potential anticancer candidate against ovarian cancer. This research work was supported by a grant from the National Institutes of Health (Grant No. NIMHD-G12MD007581). Citation Format: Ariane T. Mbemi. Novel edible medicinal plant induced cytotoxic and apoptotic effects on ovarian cancer cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4394.

Phytochemical composition of crude extracts derived from Vernonia spp. and its larvicidal activity against Anopheles gambiae

Tarwish B, Ngeranwa JJN, Matasyoh JC. 2017. Larvicidal activity and phytochemical composition of crude extracts derived from Vernonia spp. against Anopheles gambiae. Bonorowo Wetlands 1: 108-116. This study aimed to elucidate the larvicidal activity of three species of Vernonia, i.e., Vernonia lasiopus, V. auriculifera and V. galamensis against the malaria vector Anopheles gambiae. Dried samples from leaves and roots of the three plants were sequentially extracted with hexane, chloroform, ethyl acetate, acetone, methanol, and water. Following rotor evaporation of the solvents, the extracts were subjected to phytochemical analysis and larvicidal assays against the third instar larvae of A. gambiae. The phytochemical screening revealed the presence of steroids, saponins, flavonoids, terpenoids, and cardiac glycosides in all extracts. Tannins were present in methanol and water extracts of all the three plants and acetone extract of V. lasiopus roots, V. auriculifera root, and V. galamensis leaf. Phlobatannins were absent in all extracts. Percent mortality for different concentration 125, 250, 500, 750 and 1000 ppm of the extracts was calculated and subsequently subjected to probit regression analysis to determine LC50 and LC90 values. The most active extract recorded was that of acetone root extract of V. galamensis with an LC50 of 22.85. Vernonia auriculifera and V. lasiopus recorded the highest activity in acetone root extract, and ethyl acetate root extract with an LC50 value of 37.7 and 205.9 respectively. One-Way ANOVA test was performed to compare the mean mortality of all tested groups. At all exposure hours except at 3 hours, the differences were found to be significant. The Tukey post hoc tests indicated that the mortality rate for V. galamensis was substantially different from the mortality rates of V. lasiopus and V. auriculifera after 24 hours. This study underlines V. lasiopus, V. auriculifera, and V. galamensis as an alternative source of new, cheap and readily available larvicides for control of the mosquito vector A. gambiae. Further study is required to determine what secondary metabolites in Vernonia extracts are responsible for the larvicidal activity.

English

The study of pollen dispersal and mode of fertilization of Vernonia amygdalina and Vernonia calvoana is a prerequisite to the understanding of genetic diversity and elaboration of improvement programs for the Vernonia genus. In this study, precise experimental designs were made for morphological and biological observations on Vernonia species capitulum in order to assess the distinctive effects of each of the three possible pollen transportation agents (insects, wind and rain water) on pollination. Results obtained show that the exclusive mode of pollen dispersal is entomophilous. Even though allogamy and autogamy are observed as two possible modes of fertilization in Vernonia spp., some arguments tend to favour allogamy. However, there is no clear cut position on the issue, hence the need for confirmation by further experimentation in controlled pollination. This study paves the way for the establishment of a genetic improvement program for this genus based on the results on pollen dispersal. Key words: Vernonia species, allogamy, autogamy, pollination agent.

Vernonia occulta (Asteraceae: Vernonieae: Vernoniinae) a New Species from the State of Oaxaca, Mexico

Abstract A new species, Vernonia occulta (Asteraceae, Vernonieae), from the state of Oaxaca, Mexico is described. The new taxon is distinguished from Vernonia cronquistii, which is also distributed in this region, by fewer florets per head, linear-lanceolate leaves, and different leaf trichomes: the new taxon has uniseriate trichomes with four to six basal cells and one subulate apical cell, while V. cronquistii has lageniform trichomes. We also include an artificial identification key to the Mexican species of the genus Vernonia s. s.

Nine species from Madagascar are moved from Vernonia to Distephanus (Compositae, Vernonieae).

The genus Distephanus is native to Madagascar, the Mauritius, central and southern Africa, Yemen (Socotra Island), and China. The majority of the diversity is found in Madagascar. Here we provide new combinations for nine species of Vernonia that belong in Distephanus, all from Madagascar. All of the species were formerly placed in the large genus Vernonia, now greatly reduced.