The Rebbeim were particular their Esrog be from Calabria-Yanov. Rabbi Yisrael Jacobson in his sefer Zikoron L’Bnei Yisrael, p. 46, relates that in 1914, the Rebbe Rashab wasn’t able to purchase an Esrog from Calabria because of World War One. They sent the Rebbe an Esrog from Eretz Yisrael. The Rebbe became sick from not having a Calbria Esrog. He had fever and his face swelled up. He couldn’t go to shul the first two days yom tov!