The genus Onobrychis Mill. is one of the most economically important members of the family Fabaceae, which has a complicated infrageneric taxonomy. The genus has been traditionally divided into two subgenera, in which species of each subgenus have been classifed in some sections. In the present study, the macro- and micro-morphological characteristics of legumes in three sections of the subgenus Sisyrosema were evaluated using scanning electron microscopy and light microscopy techniques. In total, 10 qualitative and quantitative traits were examined with 15 replicates per trait. PAST software and the multivariate statistical program were used for statistical data analyses. All taxa have one-segmented legumes, and their dimensions signifcantly vary among the taxa. The legume’s shape varied between elliptic, circular, semicircular, and reniform, however; the most common shape was detected as reniform. Additionally, fruit in half of the taxa had dorsi-ventral symmetry. The legume outline view was detected as plumose, smooth, and short hispid, with the plumose as the abundant form. The exocarp surface indumentum was observed as glabrous, plumose (the most frequently-occurring shape), tomentose, pilose, villous, pubescent, puberulouse, plumose+villous, and short hispid+silky. The exocarp sculpturing pattern was observed as uni-formed reticulate (Afghanica and Heliobrychis) and hetero-formed reticulate (Hymenobrychis). In some cases, the taxa classifcation pattern did not follow species grouping in sections according to Flora Iranica. All the examined traits present a lack of taxonomic value at the section level. Among the characteristics, legumes shape and exocarp sculpturing patterns can be considered as diagnostic traits at the species level. However, the indumentum type, color, and shape of legumes, and their dorsi-ventral symmetry have limited taxonomic value at the infraspecifc level. Our results support the nonmonophyly hypothesis of these sections, however, the taxonomic level of some infraspecifc taxa must be updated to species.
