Of Persimmons and Whiskey

One of the difficulties in breeding minor fruits like persimmons is that most trees are either female or male.

Obviously, it is easy to judge the female tree for fruit qualities:

• Size
• Flavor
• Texture
  
• Seed size
• Season of ripening
• Color(s)

But to breed the next generation one needs pollen. And how do you judge the genetic potential for fruit quality of an individual pollen tree that does not bear fruit?

Imagine, for instance, you were trying to create a new breed of dog. For the sake of argument you wanted to create a 35 pound German Shepherd with the hips of a German Shorthair. Now imagine that you only control the females of the line, basically you are forced to allow any dogs in the neighborhood to breed her. You would not make very rapid progress toward your goal, would you.

Fortunately, there are a few selections of persimmon that have excellent fruit AND bear the occasional, rare male flower. Those selections have born the lion's share of breeding duties from the paternal side of things.

The issue with continuing down that path is the likelihood of narrowing genetic diversity and inbreeding depression, that is, genetic bottlenecking.

That is how I happened to be reading about the manipulation of gender manifestation of higher order plants.

You see, the actual chromosome (XX or XY) in question does not actually inform the developing tissue whether it should manifest as a male flower or female flower. Rather, the chromosome sets into motion an entire domino-toppling sequence of chemical reactions.

For example, there is an entire industry built around "feminized" cannabis seeds. The basic biology is to take one plant (preferably a proven clone) and either douse it with gibberellic acid solution or to interfere with the copper metabolism of the plant to inhibit the formation of ethylene...which is essential to tipping the developing tissue into female buds. If they don't form females then they default into male, pollen producing flowers.

So it begs the question: Could a plant breeder tip one branch on each of his male persimmon trees into producing fruit if he could find a way to introduce enough ethylene? That is, can he tip the differentiation in the other direction Male-to-Female? It is likely that most of the males will produce persimmons that taste like ca-ca. We only need a few more high-potential male blood-lines at this point.

The part about the whiskey

The Japanese discovered that they can hasten the ripening of under-ripe persimmons by spraying them with ethanol, that is, whiskey.

Ethylene: C2H4

Ethanol: C2H5-OH

Ethylene Glycol C2H4-2OH

The critical point is that at least some of the metabolic processes normally triggered by ethylene (fruit ripening) can be triggered with ethanol in Asian persimmons (Diopyros kaki). 

Ethanol and ethylene glycol are inexpensive and easy to buy. Ethanol or ethylene glycol might look enough like ethylene to the tissue as it differentiates to fool it into producing female blossoms and then fruit. It might be an economical way to see what those male trees "have under the hood" with regard to potential fruit quality and breeding potential.