New Genetics Study Reveals Ancient Maya Cultivated the Papaya

Do you like papaya? Then you may have the ancient Maya to thank. A new genetics study on cultivated papaya has found that the hermaphrodite version of the plant, which is of the most use to growers, arose as a result of human selection, possibly by the ancient Maya, about 4,000 years ago.

"This research will one day lead to the development of a papaya that produces only hermaphrodite offspring, an advance that will enhance papaya root and canopy development while radically cutting papaya growers' production costs and their use of fertilizers and water," said Ray Ming, one of the researchers, in a news release.

Papaya plants are either male, female, or hermaphrodite. The hermaphrodite, though, produce the fruit that's sold commercially. However, growing hermaphrodites is costly and inefficient since one-third of hermaphrodite fruit seeds and one-half of the female fruit seeds generate female plants. Farmers can't tell which seeds are hermaphrodites until the plant has flowered, so they plant multiple seeds together for the chance of getting at least one hermaphrodite plant.

The Y chromosome in papaya hermaphrodites arises from an altered form of the male Y chromosome. Researchers are interested in understanding the genetics so that they can create "true-breeding" hermaphrodite papaya.

In this case, the scientists sequenced and compared male-specific and hermaphrodite-specific regions of the sex chromosomes in 24 wild male papaya and 12 cultivated hermaphrodite sequences.

In the end, the scientists discovered three distinct wild populations: MSY1, MSY2 and MSY3. This revealed that MSY3 was most closely related to the hermaphrodite sex chromosome. In addition, all of the MSY3 plants in the study were from the northwest Pacific coast of Costa Rica.

"Our analyses date the divergence (of male and hermaphrodite papaya) to around 4,000 years ago, well after the domestication of crop plants in the Mesoamerica more than 6,200 years ago, and coinciding with the rise of the Maya civilization about 4,000 years ago," write the authors.

The findings are published in the journal Genome Research.

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