Rhobs el Arsa
The Rhobs al Arsa has long been viewed as a citron hybrid, though a different cultivars have been suggested for the parent, for example, Moroccan citron as a male parent and sour orange as the female parent, citron or lemon and a mandarin., or citron and the lime. Detailed genomic analysis has shown Rhobs al Arsa to be highly similar to several cultivars of "Citrus limetta", the limetta or Persian sweet lime, and likely shared a common origin with them, arising from a cross between citron ("Citrus medica") and sour orange ("Citrus" × "aurantium"). The common lemon arose from a distinct hybridization event involving the same two species.
Watermelon
Citrullus lanatus is a plant species in the family Cucurbitaceae, a vine-like (scrambler and trailer) flowering plant originating in West Africa. It is cultivated for its fruit. The subdivision of this species into two varieties, watermelons ("Citrullus lanatus" (Thunb.) var. "lanatus") and citron melons ("Citrullus lanatus" var. "citroides" (L. H. Bailey) Mansf.), originated with the erroneous synonymization of "Citrullus lanatus" (Thunb.) Matsum. & Nakai and "Citrullus vulgaris" Schrad. by L.H. Bailey in 1930. Molecular data including sequences from the original collection of Thunberg and other relevant type material, show that the sweet watermelon ("Citrullus vulgaris" Schrad.) and the bitter wooly melon "Citrullus lanatus" (Thunb.) Matsum. & Nakai are not closely related to each other. Since 1930, thousands of papers have misapplied the name "Citrullus lanatus" (Thunb.) Matsum. & Nakai for the watermelon, and a proposal to conserve the name with this meaning was accepted by the relevant nomenclatural committee and confirmed at the International Botanical Congress in Shenzhen.