| Name | Accession number | Synonym | Species | Habit | Locality |
|---|---|---|---|---|---|
| ONOCROTALUS | CD-68458[1281][3692]; | TR.DR | S | MEX | |
| ONODI | K-51372; AUS-15792 | TR.AE | W | HUN | |
| ONOKHOISKAYA-2433 | TR.AE | S | RUS:Buryatiya | ||
| ONOKHOISKAYA-4 | K-41369; AUS-10550 | TR.AE | S | RUS:Buryatiya | |
| ONOKHOISKAYA-6 | LUTESCENS-M-756[1447]; | TR.AE | S | RUS:Buryatiya | |
| ONOLDIA | PI-351574 | WAHRBERGER-ONOLDIA[39]; | TR.AE | S | DEU |
| ONRAITA | TR.AE | ESP | |||
| ONTARIO | PI-610450 | W-94-137-152[2965]; | TR.AE | W | USA:Kansas |
| ONTARIO-4313-51-10 | TR.AE | CAN | |||
| ONTARIO-WONDER | K-5809; CI-3483; AUS-6968 | TR.AE | W | CAN | |
| ONYX | K-51946; ERGE-2950 | TR.AE | W | FRA | |
| OOIVAAR | CD-87349[1281][3692]; | TR.DR | S | MEX | |
| OOM-CHARL | TR.AE | S | ZAF | ||
| OOURADO | TR.AE | PRT | |||
| OO-VOZ | K-24958 | TR.AE | I | JPN | |
| OPAKS-1 | K-58894 | TR.AE | W | KAZ:Alma-Ata | |
| OPAKS-18 | K-60686 | TR.AE | W | KAZ:Alma-Ata | |
| OPAKS-2 | K-55184 | TR.AE | W | KAZ:Alma-Ata | |
| OPAKS-26 | K-61231 | TR.AE | W | KAZ:Alma-Ata | |
| OPAKS-3 | LINE-7468[3812]; | TR.AE | W | KAZ |