Yam (Dioscorea spp.) and its associated extracts have been shown to possess a variety of biological activities and identified as beneficial in the control of glycaemia in patients with type II diabetes mellitus (T2DM). The objective was to conduct a systematic search of the literature to investigate whether yam and its extract can improve glycaemia and whether the consumption of yam could be beneficial for managing T2DM. Using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines and the Population, Invention, Comparison and Outcome framework, three databases (PubMed, Scopus and Web of Science) were searched using a key term strategy. Strict inclusion criteria were employed to identify all relevant and available studies. The quality of these studies was assessed using SYRCLE’s Risk of Bias tool. Ten studies were included, and all studies consisted of findings from rodent models of diabetes, including animals consuming high fat diets or genetic models of diabetes. All ten studies showed that the consumption of yam and/or its extracts (containing dioscin, dioscorin, diosgenin, DA-9801/02 or Chinese yam polysaccharides) improved glycaemia. These included improvements in fasting blood glucose and reductions in glucose and increase in insulin levels following a glucose tolerance test. Furthermore, significant changes in body weight and adiposity were observed in nine studies, these included improvements in lipid biomarkers in four and reductions in inflammatory markers in one. The current work indicates that the consumption of yam or its extracts can be beneficial for improving blood glucose; however, the molecular mechanism for these effects remains largely unknown. Future trials on human subjects are warranted.

Development of core collection representing the diversity in the entire germplasm creates a better access and enhanced utilization of the main collection thus allowing rapid evaluation in crop improvement programs. Core collections are dynamic in nature and needs revisiting when additional germplasm and information becomes available. In the current study, an attempt was made to re-define the previously developed yam (Dioscorea spp) core collection using 56 morphological traits. Information on additional acquired germplasm and presence of duplicates or mislabelled accessions in the entire collection was also used. The re-defined core collection consisted of 843 accessions and represented about 20% of the entire collection. It included six Dioscorea species, of which accessions of Dioscorea rotundata are in the majority (73.54%) followed by Dioscorea alata (21.35%), Dioscorea bulbifera (1.66%), Dioscorea cayenensis (1.42%), Dioscorea dumetorum (1.42%) and Dioscorea esculenta (0.59%). The Shannon weaver diversity index and principal component analysis revealed the maximum diversity captured in the core from the base collection. This re-defined core collection is more valuable than the original core since it represents true-to-type accessions ensuring reliability for enhanced utilization of germplasm in yam improvement programs.

There are three native varieties of edible yams (Dioscorea japonica Thunb.) in Taiwan, but germplasm has been collected from only a few. To assess the genetic diversity of 99 accessions collected from four geographically diverse regions, inter-simple sequence repeat (ISSR) DNA markers were analysed, and 90.2% of the polymorphic markers in these accessions were found. Genetic similarity among accessions ranged from 30.8 to 74.4%, averaging 48.4%. Cluster analyses revealed four main clusters plus one outlier (Dioscorea alata L.). The varieties oldhamii and pseudojaponica were separated into different clusters and var. japonica was grouped with both varieties. Since var. japonica was found to be genetically similar to var. oldhamii and var. pseudojaponica, we suggest that var. japonica is a hybrid or intermediate variety between the two varieties. Molecular analysis of variance results indicated that variation within counties (95.94%) was predominantly greater than variation among counties (3.63%) and among regions (0.43%). Overall, gene flow (Nm= 0.970) estimated from genetic differentiation (Gst= 0.340) suggests that gene flow among regions is relatively high. The highest genetic diversity (H= 0.191) and Shannon's index (I= 0.312), and a high gene flow (Nm= 3.926) of germplasm in the northern region suggest that this region is a possible centre of dispersal and domestication of yams in Taiwan. This study provided valuable information for germplasm collection and genetic improvement.

Did the banana, yam and taro arrive in Australia at the hands of Europeans or come across the Torres Strait 2000 years before? Reviewing the evidence from herbaria histories and anthropology, the authors propose a ‘hierarchy of hypotheses’ and consider a still earlier option, that these food plants were potentially grown in Australia at least 8000 years ago, while it was still joined to New Guinea. This hypothesis, first proposed by Jones and Meehan in 1989, locates early horticultural experiments among peoples too often seen as inveterate hunter-gatherers.

Guinea yam (Dioscorea rotundata Poir.) is a dioecious vegetatively propagated tuber crop. It is widely cultivated by traditional techniques in West Africa, its area of origin. The genetic diversity of 146 accessions from Benin was analysed using 10 polymorphic simple sequence repeat (SSR) nuclear markers and agromorphological traits. An average of 8.4 alleles per locus was detected. The mean heterozygosity was 0.57 and the mean polymorphism information content (PIC) for polymorphic markers was 0.51. Some cultivars (23%) were found to have an identical genotype for the 10 markers. The structure of the genetic diversity observed in Benin is the result of farmers' crop management practices and their know-how. The cultivar diversity had a geographical component. We also noted major differentiation between early and late cultivars, with higher diversity in the early ones. Cultivars from northern Benin and early cultivars had the greatest allelic richness. SSR markers proved to be powerful tools for fingerprinting each cultivar and analysing their genetic relationships. The results of this study could be useful for defining a strategy for the conservation of genetic diversity in yams.