Intersexing the papaya plants


You know, just when you were thinking you were starting to get the swing of things, the Universe throws another curveball.

Apparently there are three naturally occurring genders of papaya trees: male, female and hermaphrodite. While that’s not abnormal, per se, since human gender shows the same diversity, what I didn’t know was that most of the papaya fruit that we consume comes from the more highly prized hermaphrodite papaya trees. It seems the fruit from the “intersexed” trees is much sweeter than the male or female trees fruit.

So agricultural biologists are going to do a little tweaking to make the sweeter variety which is already relatively common, much more common.

“‘We’re going to change the sex of the papaya to help the farmers,’ said University of Illinois plant biology professor Ray Ming, who will lead the effort with researchers from the Hawaii Agriculture Research Center, Texas A&M University and Miami University. A USDA scientist will also collaborate on the initiative.

‘This is a perfect case to demonstrate how basic science can help the farmers directly,’ Ming said. ‘In our case we can apply it immediately as a byproduct of the research program.’
Papayas already come in three sexual varieties: male, female and hermaphrodite. The hermaphrodite produces the flavorful fruit that is sold commercially. From the grower’s perspective, however, hermaphrodite plants come with a severe handicap: their seeds produce some female plants (which are useless commercially) and some hermaphrodites.

The problem is exacerbated by the fact that it is impossible to tell the sex of a seed until it has grown up and flowered. This means that papaya farmers must plant five or more seeds together to maximize the likelihood of obtaining at least one hermaphrodite plant. Once they identify a desired plant, they cut the others down.”

The plan is to carefully examine the Y chromosome in the plant, identify the gene which controls the gender switch from female to hermaphrodite plants and through standard manipulation techniques make a hermaphrodite plant that only produces hermaphrodite offspring.

Read the full article here.

What an interesting action the free market and economic pressure is driving. Or I guess we could call this evolution in action – given that the cultivated papaya tree is in a sort of symbiotic relationship with human beings.

The Author

Episcopal bishop, dad, astronomer, erstwhile dancer...


  1. In a program I recently saw on PBS called “The Botany of Desire based on the book by Michael Pollan they discuss the way plants have used a strategy of adapting traits that humans desire to survive. It looks at how plants have used the human desire for sweet taste, beauty, chemical highs and others to entice humans into helping them thrive and to be propagted to new areas. It compares human activity to a bee that thinks it is getting the best of a relationship from a flower when it gets the nectar. In reality the flower produces the nectar to allow for the plant to pollinate and survive. The papaya story is another example that demonstrates how humans are just one more factor in evolution and not outside of it.
    Thinking of myself as participant in evolution and not an outside uninvolved observer certainly makes me wonder about the world we are helping to create for God. We are not just occasionally stepping in to pass some law to influence the survival of a species but making choices from the food we select at the grocery, the flowers we put in our yards and the way we chose to celebrate that will determine what the plant and animal world our children inherit will look like.

  2. There’s actually a huge agricultural research program on sheep for analogous reasons. Seems that a substantial fraction of rams (upwards of 8%) are homosexual, and a similar fraction are asexual. Quite a cost for sheep farmers who tend to have one ram for a flock of ewes.

  3. Following up on Robert’s point… I once heard Rush Limbaugh absolve human beings of any complicity for anthropogenic global warming because, as he pointed out, all global warming must be of natural causes. Because human beings are part of nature.
    So I’m wondering if those who make the argument that the world needs to be clearly divided into either/or categories because that is what is natural (as the Roman Catholic Church seems to be formally arguing these days) might be challenged by the “natural” selection which is leading to larger numbers of third or intersexed genders in nature. (In addition the the sheep that IT mentions, there is the question of the date palm as well according to a commentator over on the facebook version of this post, and I’m sure there are more.)
    I’ve been concerned that we tend to do ethics by relying to heavily on binary thinking. Maybe we’re seeing a definitive counter-example?

  4. Christopher says

    Given the array of sexual differentiation (and not) possibilities in nature, I still remain astounded that we act stunned that human beings might also be more complex than simplistic binaries of the romanticized sort that is floating around in Christian circles. What is even more astounding are assertions of complementarity that posit romanticized difference when Gen. 2 says just the opposite. Male and female are not opposites that complement one another, but similars that supplement one another. And any observer of real persons knows that the qualities we associate with the “pure type” of each are on a multivalent scale.
    Irrespective of the diversity among human beings in this regard, we are of one flesh, and that requires thinking that ethics apply with equity across the board. As it is, we apply double-standards of ethics depending on the composition of pairs among humans. We cannot locate ethics in the composition, but in the virtues we desire to see born out irrespective of that pair composition. Otherwise, we end up with idols.

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