The important role of the Jewish religion in the widespread adoption of citrus fruit by early Mediterranean societies has been discovered by genetic detective work at the John Innes Centre; as a result of an investigation into an acid-less mutation which makes citrus juice 1000 times less acidic. Citron is one of four primary species that make up the citrus genus, a complex group of flowering plants with notable nutritional, medicinal and aromatic value.
The citron was the first citrus species to be cultivated in the Mediterranean. Some people thought that the acid-less mutation originated in Corsica, or in the eastern Mediterranean, but we found that the mutation is not new. It’s an ancient mutation that is present in Chinese fingered citrons known as Buddha’s Hands; and in citrons used ritually in the Jewish harvest festival of Sukkot.
The acid-less mutations have captivated botanists and breeders for centuries; and appear in many citrus varieties including citron, sweet lime, limetta, lemon and sweet orange. The researchers identified a gene, which they called Noemi, as the key factor behind the regulation of fruit acidity.
The Noemi mutation was found in fingered citron varieties first cultivated in China 3300 years ago, about the time of Moses. The Torah enjoins: “On the first day [of the Sukkot harvest festival] you shall take the fruit of goodly trees, branches of palm-trees, boughs of thick trees, and willows of the brook, and rejoice before the LORD your God [for] seven days (Leviticus 23:40).
While the Torah passage names the palm frond, the willow, and possibly the myrtle, it does not name the fruit of goodly trees. In fact, the name etrog is not found anywhere in the Bible. The Hebrew peri etz hadar “the fruit of goodly trees” or, “the goodly fruit of trees” indicates only that the fruit had good medicinal effects.
Indeed, “Citron was first cultivated for its medicinal properties in China and its rind was used as a medicinal product, not as a food” says Professor Cathie Martin, a co-author on the study.
This is supported by the Chinese name for fingered citrons called Buddha’s Hands due to the etrog’s healing qualities. The etrog’s connection with the Buddha, who died c.480 BCE, must have come from Buddhist missionaries who entered China during the last half of the Han empire (206 BCE- 220 CE).
The ancient Noemi allele characteristic of the acid-less trait was present in the Yemen citron, an ancient variety traditionally used in the Sukkot tradition after the time of the destruction of the first temple in 587 B.C.E.
The analysis suggests that the authentic Jewish Etrog used ritually for Sukkot was an acid-less one, an idea supported by a reference to “sweet citron” in the Mishna, a Jewish legal text, dating from 200 C.E.
The study which appeared in Current Biology illuminates the path of domestication of the citron. It supports the view that the spread of the citron in Mediterranean regions was facilitated by its widespread use in Jewish culture as an important religious symbol.
The study also gives researchers the information they need to develop fruit for the future — to modulate their level of acidity and to increase their content of health-protecting anthocyanin compounds and make them into goodly fruit trees.