The Yemenite citron (Hebrew: אֶתְרוֹג תֵּימָנִי, etrog teimani) is a distinct variety, usually containing no juice vesicles in its fruit's segments. The bearing tree is fairly bigger than the trees of the different varieties of citron, and the fruit's albedo is notably juicier.
Despite its differences from standard varieties, the Yemenite citron was attested by a group of citrus and genetic experts to be a true variety of citron and possessing a close genetic relation with the rest of the types. A brief documentation of this study was presented at the Global Citrus Germplasm Network.
Although other varieties of pulpless citron, such as Buddha's hand, can be found in India and China, most Jewish cultures are not aware of them. The Yemenite Jews say it went with them through tradition, and even believe it was in their hands since The First Temple.
Some argue that the absence of pulp is clear evidence for its genetic purity, and that other varieties developed a pulp due to being grafted upon Lemon or Orange rootstock. This assertion is contested by virtue of the fact that the fruits of a Yemenite tree at the Citrus Variety Collection contain no pulp despite being grafted on foreign rootstock.
|Citrus • Succade • Hybrid • Grafting • Chimera • Etrog • Sukkoth • Four Species
Current research shows that grafting would not result in any hybridization, which can only be obtained by cross breeding achieved by applying the pollen of one variety or species to the style of another species. In light of this, there is no reason to question one traditional variety more than another, especially when the above genetic study shows equal purity for all. In particular it shows high affiliation between the "Yemenite" kind and the Diamante citron. However this is not a proof for the etrogs from every individual grower.
Etrog haCushi 
Etrog haCushi (Hebrew: אֶתְרוֹג הַכּוּשִׁי) is mentioned in the Mishnah as well as in both the Babylonian (Succa 36a) and the Jerusalem Talmud (Succa 3:6). The most common interpretation is that the Biblical Cush refers to Ethiopia, and therefor Etrog haKuschi should also refer to something which could be called the Ethiopian citron.
The Ethiopian Jews did not follow the mitzva of four species, even though they did anticipate the Sukkot festival, as well as the rest of the Jewish ethnic divisions. This may have been due to their lack of ability to procure the species. Some believe that this is due to some Karaite influence, whose biblical interpretation indicates that the four species are only used as roofing for a sukkah (the S'chach), and not for a separate waving ritual.
However, the Yemenite citron is available in Ethiopia and its markets, where it is sold for consumption. According to Erich Isaac, the late researcher of citrus distribution, the Yemenite citron is synonymous with the Ethiopian citron as a result of Ethiopian rule of Yemen in the past.
See also 
- Hebrew Forum with Participation of Growers
- A Man Holds A Yemenite Citron against his Head
- Yemenite Citron by the CVC of UCR
- Global Citrus Germplasm Network, page 19. The full document could be purchased by IBIDS
- The Purdue University describing all different citron varieties along the world.
- Agitation for the Yemenite Citron, Hebrew
- Bar Ilan University article about the subject.
- David Schperber
- See also שאילת שלמה
- Ari Greenspan
- Yemen Times
- Influence of Religion on the Spread of Citrus; by Erich Isaac