Short answers, pulled from the story.
Grapefruit originated in Barbados in the 18th century as a natural hybrid between the sweet orange (Citrus sinensis) and the Indonesian pomelo (Citrus maxima), both of which had been introduced to the Caribbean from Asia. The crossing occurred without human intervention, and the fruit was first documented in 1750 by the Reverend Griffith Hughes in The Natural History of Barbados.
The British naturalist John Lunan published the term grapefruit in 1814, suggesting the name referred to the fruit's similarity in taste to the grape, Vitis vinifera. An alternative explanation is that the name alludes to clusters of the fruit on the tree, which resemble bunches of grapes.
Grapefruit contains furanocoumarins, including bergamottin and 6',7'-dihydroxybergamottin, which inhibit the CYP3A4 enzyme responsible for metabolizing roughly 90% of drugs. One whole grapefruit or 200 ml of juice is enough to cause drug overdose toxicity with incompatible medications. Adverse effects can include abnormal heart rhythms, gastrointestinal bleeding, low blood pressure, and respiratory depression.
The Rio Red variety was developed by treating bud sticks with thermal neutrons to induce mutations that preserved and deepened the red pigment, which tends to fade to pink in unmodified varieties. It was registered as a Texas grapefruit in 1984 and carries trademarks including Rio Star and Ruby-Sweet.
Count Odet Philippe, a French businessman, brought grapefruit to Florida in 1823, planting it in what is now known as Safety Harbor. An entrepreneur named Kimball C. Atwood later founded the Atwood Grapefruit Company, which grew into the largest grapefruit grove in the world with a yearly output of 80,000 boxes.
In 2023, world production of grapefruits combined with pomelos reached 9.93 million tonnes. China led global production with 52% of the total, with Vietnam as a secondary producer.