Citron
There are also a number of citron hybrids; for example, ponderosa lemon, the lumia and rhobs el Arsa are known citron hybrids, some are claiming that even the Florentine citron is not pure citron, but a citron hybrid.
Mal secco
The main host of mal secco is the lemon; however other genera including Citrus, Severina, Fortunella, and Poncirus have all been reported to be susceptible. In addition to lemon, the disease has been observed to be highly destructive in Citron (C. "medica L".), lime (C. "latifolia Tan".), and bergamot (C. "bergamia Risso"). The most common lemons in the Mediterranean, the rough lemon (C. "jambiri Lush"), volkamer lemon (C. "volkameriana Ten. & Pasq".), and alemow (C. "macrophilla wester") are very susceptible.