Do you know the Angiosperm Phylogeny Website (http://www.mobot.org/MOBOT/research/APweb/)? Search under the Fabales in the side bar on the left hand side, following to the Fabaceae. I think however that there's no direct reference to Trigonella.
Thank you for answers. Indeed there is no direct link to Trigonella species in AP website. I think that now the systematics may be more complicated than earlier.
Barbara, try GRIN-Taxonomy, they follow APG, and it might provide information that you are looking for. The site is http://www.ars-grin.gov/cgi-bin/npgs/html/splist.pl?12360
Thank you Blanca, I haven't known this page. It seems that some of Trigonella species are indeed now the Medicago, yet T. foenum-graecum was left without major changes. Thank you very much!