The papaya we know and love today (hello, delicious fruit salad addition) can actually be pretty tricky to produce.
The fruit grows on a tree that comes in one of three sexes—male, female, or hermaphrodite—but only the hermaphrodite versions have the large yields preferred by almost all commercial growers. But farmers can’t tell which seeds will grow the desired plants. So, they put a bunch of seeds in the ground at once, wait for them to grow and then chop down the between one-third and one-half of plants that aren’t the hermaphrodite variety.
The whole process is costly and time consuming, which is why researchers at the University of Illinois recently launched a study to better understand the plant and the mutation that causes some to be hermaphroditic.
In evaluating the genetics of papaya sex chromosomes, the scientists came upon an interesting discovery. According to the team, lead by plant biologist Ray Ming, it appears that the hermaphrodite version “arose as a result of human selection, most likely by the ancient Maya.” As a news release explains:
The researchers sequenced and compared the “male-specific” and “hermaphrodite-specific” regions of the Y and Yh sex chromosomes, respectively, in 24 wild male papaya and 12 cultivated hermaphrodite plants. They found less than half of one percent difference between the male and hermaphrodite sequences, suggesting that the evolutionary event that caused them to diverge occurred in the not-too-distant past.
“Our analyses date the divergence (of male and hermaphrodite papaya) to around 4,000 years (ago), well after the domestication of crop plants in Mesoamerica more than 6,200 years ago, and coinciding with the rise of Maya civilization about 4,000 years ago,” the study, published in the journal Genome Research, states. The Maya people, who made up a civilization that spanned much of Central America, are well known to have been skilled farmers.
“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 Ming. The research team also noted that the relatively recent emergence of the fruit’s sex chromosomes (they’re only about 7 million years old as opposed to those of humans that are about 167 million years old) make them ideal for studying sex chromosome evolution in general.
It all goes to help remind us that there’s a long history—and valuable information—behind much of the food in our mega marts.