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.
Moroccan citron
As to the Diamante citron (Yanova) and the Greek citron (Corfu), he argued based on the booklet from the Salant partners, that since some of them are proven to be grafted, no certification may be granted to the rest, since it is impossible to determine if the non-grafted citrons are not descendants of the grafted ones.
As to the Moroccan and Yemenite citrons he argued, that although there were no grafted trees ever discovered among those kinds, they should be unfit, in light of the differentiation from the Ashkenazi types. The Moroccan citron is allegedly noted for its seedlessness, and the Yemenite for its pulplessness, both are too much different in morphology from the traditional Yanova and Israeli esrogs.