Where Do Oranges And Lemons Originally Come From?

Gayle Volk, a plant physiologist at the U.S. Department of Agriculture describes citrus as "fascinating" due to many of the crops processed through hybridization. Citruses have a huge genetic diversity, unlike any other fruit. This recent research has opened up the exploration of the citruses' evolutionary journey. They analyze the genomes of numerous citruses and then study the uncovered insights into the origin of these fruits. Recent hypotheses have stated the origin of citruses was from the Himalayas to northeastern Australia, but after further study, they figured out they originated from south-central China.

The research team at the Huazong Agricultural University in China assembled genomes from a dozen species and compared them with existing genetic records. This then led to them making a phylogenetic tree, and an evolutionary tree, these provided good information on the origin of where they are from. The trees also revealed that citrus plants emerged over 25 million years ago. Mandarins and trifoliate oranges began evolving in south-central China, and other citruses such as pomelo and citron evolved slightly later.

Understanding the genetic origins of citrus has significant implications for their preservation and conservation during environmental challenges such as pests and diseases. Gayle Volk emphasizes the importance of refining the genetic origins for effective conservation. Overall, this genetic study offers us a good glimpse into the complex history of citrus fruits. It shows not just their evolutionary journey but also the critical role genetics play in shaping their flavors and looks. 

Articles: 

Sci Am Article

Evolution in the Citruses

Genetics of Sourness

In a Cosmos article, the sourness of fruits are discussed and originates from the acidity of the vacuole. The vacuole is somewhat acidic due to the fact that hydrogen ions are pumped into it. The more hydrogen ions that are pumped, the more acidity. Citrus fruit have varieties that express gees CitPH1 and CitPH5 which encode for transporter proteins that amplify the pumping of ions increasing the concentrations. These genes were had an reduced expression in sweet or low acidic  like fruits. This can be beneficial to breeders for tastier fruits.

I love sour fruits so I was intrigued to read this article. I had learned that the purpose of a vacuole was for storage of different of nutrients, toxins, and aids in hydrostatic pressure. However, I was informed through this article that the sourness is derived from the amount of hydrogen ions are being pumped into it the organelle.