The secret life of etrogs

Farmers on the Greek island of Corfu had been growing widely praised etrogs for more than 100 years when, in 1846, a competitor to the Corfu growers won support from Polish and Lithuanian rabbis -- who had never seen an etrog tree -- for his claim that the Corfu etrogs were grafted and therefore unfit for ritual use.
The citron tree is not very hearty, with a weak root system that requires a lot of water and has a life span of about 15 years. By splicing a bud from the etrog tree into a branch of a lemon tree, the citron can take advantage of the heartier lemon root stock, while still maintaining all of the botanical characteristics of a citron.
Most scientists agree that a grafted fruit is identical to a nongrafted fruit, according to Karp, who is associated with the Citrus Variety Collection and has been researching citron for years.
But the Torah prohibits grafting, and even if the fruit is grafted by a non-Jewish farmer, most halachic authorities hold that a grafted etrog -- known as a murkav -- is not suitable for ritual use.
They even ban etrogs descended from the seeds of grafted fruit, leading to the need to have certified etrog lineage.An accusation of selling grafted etrogs could shutter a citron operation, but in the 19th century Corfu growers fought back, with the support of many rabbis and consumers.
The standoff continued for nearly 30 years -- including an incident where etrogs were dumped into the ocean -- until, according to the Jerusalem Post article, a blood libel scandal in Corfu led Jews from around the world to ban the etrogs, which were mostly grown by non-Jews.