CHROMOSOMAL ANALYSIS OF EIGHT CULTIVARS IN THREE SPECIES OF CULTIVATED YAM (DIOSCOREA) SPECIES IN NIGERIA

The genus Dioscorea comprises of economically-important plant species known for their starch throughout the world; it is also a major source of food and income in Africa. The most important Dioscorea species cultivated and consumed in the West Africa belt include D. cayenensis, D. rotundata and D. alata. The plant materials used in this study were collected from Omu-Ekiti, Oye Local Government of Ekiti State, Nigeria using the On Farm Participatory Method (OFPM). Mitotic chromosome studies were carried out on three species viz, Dioscorea alata (‘ewura’), D. cayenensis (‘igangan’) and D. rotundata (‘areyingbakumo’, ‘gaungaun’, ‘ikumo’, ‘ogunmole’ and ‘sandpaper’). Mitotic chromosome studies were carried out on each of the cultivars using the root tip squash method made in modified Orcein stain (FLP-Orcein). Dormant tubers were cut to mini-setts and placed in carbonised rice husk for rooting. This study reports the basic chromosome number of x = 8, i.e. 2n = 4x =32 (D. alata), 2n = 4x =38 (D. rotundata) and 2n = 8x = 68 (D. cayenensis) for Dioscorea suggesting that both D. rotundata and D. cayenensis are aneuploids.

Diversity, trait preferences, management and utilization of yams landraces (Dioscorea species): an orphan crop in DR Congo

BackgroundYam ( Dioscorea spp .) is cultivated in many villages of DR Congo as a means to sustain food security and alleviate poverty. However, the extent of the existing diversity has not been studied in details thus, considered as an orphan.MethodologyA survey covering 540 farmers in 54 villages was conducted in six major yam growing territories covering three provinces in DR Congo to investigate the diversity, management and utilization of yam landraces using pre-elaborate questionnaires.ResultsSubject to synonymy, a total of 67 landraces clones from five different species were recorded. Farmers’ challenges limiting yam production were poor tuber qualities (69%), harvest pest attack (7%), difficulty in harvesting (6%), poor soil status (6%). The overall diversity was moderate among the recorded yam germplasm maintained at the household level (1.32) and variability exist in diversity amongst the territories and provinces. Farmers’ in territories of Tshopo and Mongala provinces maintained higher level of germplasm diversity (2.79 and 2.77) compared to the farmers in territories of Bas-Uélé (1.67). Some yam landraces had limited abundance and distribution due to loss of production interest in many villages attributable to poisons contained hence, resulting in possible extinction. Farmers’ most preferred seed source for cultivation were backyard (43%) and exchange with neighboring farmers (31%) with the objective of meeting food security and generating income. In villages where yam production is expanding, farmers are relying on landraces with good tuber qualities and high yield even though they are late maturing.ConclusionThis study revealed the knowledge of yam genetic diversity, constraints to production and farmers’ preferences criteria as a guide for collection and conservation of yam genetic resources for yam improvement intervention.

The Unique Substance, Lidocaine and Biological Activityof the Dioscorea Species for Potential Application as a Cancer Treatment, Natural Pesticide and Product

The six Dioscorea species, D. brevipetiolata, D. bulbifera, D. depauperata (Dd), D. glabra (Dg), D. pyrifolia and D. hamiltonii were analyzed for phytochemicals, toxicity in PBMCs, and biological activity in two cancer cell lines by MTT and comet assays, and pesticide efficiency. Via GC-MS, lidocaine was found to be the predominant compound in two of the studied species. To confirm the systematics, lidocaine was also found in lower amounts in 11 species. The MTT assay showed no toxicity in all six of the studied species. The comet assay showed the key result that the ethanol extracts of Dd and Dg violently broke DNA into pieces. Biological activity of these two species’ extracts showed toxicity on HepG2 and no effects on HCT-116. The water extracts of Dd and Dg, applied to Brassica chinensis showed high efficiency as a bioprotectant. In summary, lidocaine seems to be the predominant identifying compound of the genus Dioscorea in Thailand, which is useful in systematics. At least the two species, Dd and Dg, may be used for human hepatocyte cancer treatment and as an alternative pesticide for economically important vegetables. Dioscorea species containing lidocaine or extracted lidocaine have promise for natural product creation.

Population Genomics of Yams: Evolution and Domestication of Dioscorea Species

Yam is a collective name of tuber crops belonging to the genus Dioscorea. Yam is important not only as a staple food crop but also as an integral component of society and culture of the millions of people who depend on it. However, due to its regional importance, yam has long been regarded as an “orphan crop” lacking a due global attention. Although this perception is changing with recent advances in genomics technologies, domestication processes of most yam species are still ambiguous. This is mainly due to the complicated evolutionary history of Dioscorea species caused by frequent hybridization and polyploidization, which is possibly caused by dioecy that imposed obligate outcrossing to the species of Dioscorea. In this chapter, we provide an overview of the evolution of Dioscorea and address the domestication of yam from population genomics perspectives by focusing on the processes of hybridization and polyploidization. A review is given to the recent population genomics studies on the hybrid origin of D. rotundata in West and Central Africa, the global dispersion of D. alata through human migrations, and the whole-genome duplication of the South America species of D. trifida. In the end, we give a summary of current understanding of sex-determination system in Dioscorea.

Some Dioscorea species.

This chapter focuses on the morphology, bioactive compound and nutrient composition, and uses of some Dioscorea species.

The Dioscorea Genus (Yam)—An Appraisal of Nutritional and Therapeutic Potentials

The quest for a food secure and safe world has led to continuous effort toward improvements of global food and health systems. While the developed countries seem to have these systems stabilized, some parts of the world still face enormous challenges. Yam (Dioscorea species) is an orphan crop, widely distributed globally; and has contributed enormously to food security especially in sub-Saharan Africa because of its role in providing nutritional benefits and income. Additionally, yam has non-nutritional components called bioactive compounds, which offer numerous health benefits ranging from prevention to treatment of degenerative diseases. Pharmaceutical application of diosgenin and dioscorin, among other compounds isolated from yam, has shown more prospects recently. Despite the benefits embedded in yam, reports on the nutritional and therapeutic potentials of yam have been fragmented and the diversity within the genus has led to much confusion. An overview of the nutritional and health importance of yam will harness the crop to meet its potential towards combating hunger and malnutrition, while improving global health. This review makes a conscious attempt to provide an overview regarding the nutritional, bioactive compositions and therapeutic potentials of yam diversity. Insights on how to increase its utilization for a greater impact are elucidated.

HUMAN BREAST TUMOUR CELLS VIABILITY EFFECT OF AFRICAN DIOSCOREA ROTUNDATA TUBER EXTRACTS IN MCF-7 AND MDA-MB231 CELL LINES

ABSTRACTObjectiveWe aim to test the efficacy of edible Dioscorea species grown and consumed in Nigeria, Africa on two breast cancer cell lines; MCF-7 and MDA-MB231 derived from a luminal and a triple-negative breast cancer (TNBC) respectively and to confirm safety in non-tumour cells MCF-10A using a well established cytotoxic compound paclitaxel as a standard. Metastatic breast cancer is a prevalent cause of mortality in women around the world. Breast cancer therapies have greatly advanced in recent years, but many patients develop cancer re-occurrence and metastasis and subsequently yield to the disease because of chemoresistance.MethodsEthanolic extracts of Dioscorea rotundata boiled and raw (DiosB and DiosR) respectively were chemically analysed for the presence of diosgenin using HPLC and the cytotoxic activity of the extracts were tested on MCF-7, MDA-MB-231 and MCF-10A cells In vitro by MTT assay.ResultsDiosB and DiosR extracts showed a higher maximal effect on MCF-7 cells than on MDA-MB231 after 24 h and 48 h treatments (p<0.0001 and p<0.05 respectively). DiosR, if applied at a range between 50-70 g/ml, can be effective to reduce breast tumor cell viability without affecting non tumorigenic MCF-10A cells either at 24 h or at 48 h. DiosB showed an IC50 of 38.83μg/ml while DiosR showed an IC50 of 41.80μg/ml.ConclusionThese results show that ethanolic extracts of Dioscorea rotundata tubers could be used effectively to treat breast cancer tumors and this is in sync with its diosgenin content as other Dioscorea species applied for similar treatments in Asia and elsewhere.