Plant sex question:. If an apple tree has both parts, why aren't they all self-fertile?

If an apple tree has male and female parts, why do so many need a cultivar?

This is sad I don’t know this.

Found this online…

Pollination Basics

  1. With perfect flowers, apple blossoms have the potential for self-pollination – each blossom houses both male and female reproductive parts. However, seed production has better diversity and genetic strength with cross-pollination. As insects feed on the flowers’ nectar, pollen grains adhere to their bodies. Moving between flowers for sustenance, insects press the grains removed from the flower stamens onto other stigmas. As a result, the flower becomes fertilized as the grain forms a tube to move the pollen down into the ovule. However, successful apple fertilization does not occur unless the cross-pollination process mixes two different varieties together. For example, a “Red Delicious” cannot fertilize another “Red Delicious” tree.

Doesn’t that contradict itself, or at least not tell everything? It doesn’t tell me if red delicious is one of the perfect flowers. I found several things online, but nothing specific, yet.

This Wikipedia article explains: Self-incompatibility (from the article: SI is one of the most important means of preventing inbreeding and promoting the generation of new genotypes in plants and it is considered one of the causes of the spread and success of angiosperms on the earth.)

And there are a number of self-fertile (Self-compatibility) apple varieties. I have one.

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This is really quite a big rabbit hole to go down. I don’t know enough to truly teach anything, but I may know enough to enhance your current framework.

  • Timing of the fertility is generally not supportive of self-pollination in perfect flowers. The male parts and the female parts are not necessarily mature at the same time.
  • Genetic selection is going to favor diversity. I couldn’t begin to tell you how this functions in an apple, but plants that have an option for a partner are going to be more receptive to the option than to themselves. Maybe the myccorhiza/root web somehow convers the presence of other trees, maybe there is something along the lines of a pherome carried in the wind. Maybe something gets turned off after too many seasons without pollination. Probably it is something I have never heard of yet. It is likely competition based, because life wants to find a way and it prefers it not to be a dead end. Things that favor self in their environment tend to have less resource intensive ways to self-propagate (rhizomes, sprouts, etc.)

The Bardsey Apple, on Bardsey Island, apparently fruited rather well for quite a long time, despite a lack of any other pollinators on the island, which is something like 3 miles out to sea; but, that same tree in our gardens needs a pollinator. (I have not visited this mother tree, so I do not know how much of the data around it is hype or sanitized to fuel interest.)

You might be familiar with blood types. In humans you can have Type A,B, both or neither type O. Blood types are actually referring to antigens to blood. eg does your body will recognize a blood protein as its own or attack it. People with type B blood do not have the antigen attacking type B blood protein. But they will attack type A blood protein. In Cherry’s for example several s- alleles exist that govern compatibility.

Bing and not fertilize emperor since both have s3S4 and Cherry’s by nature reject pollen with of its own type. This is designed to keep the species diverse and protect from inbreeding.

I’ll fix this post later when I’m not on my phone.


the cool thing with cherries specifically is there were radiation-induced mutation experiments in the 50s that produced “broken” pollen so the plant’s self infertility mechanism doesn’t work anymore. many cherries today contain the same s3’ or s4’ genes that were created back then. here’s the original article on it. coming up with this same kind of gene for other fruits especially plums could be a big win

I think its a bad idea and a good idea. If Self compatability would let people plant 1 tree to get fruit. Thats good for getting suckers to buy more trees from home depot. But its also bad because it would create huge mono cultures of one cultivar to obtain identical comercial cherry production. Thank Red and Yellow Delicious. YD is largely self fertile and a good pollenator so we have massive plantings of just YD and RD and half of the “new” grocery store cultivars have YD as a parrent or are a “chance” seedling from a YD RD grove.

On the other hand if it could render plum and peach more comptable with cherry. That might produce some interesting fruit. But I fear it would be applied to the most bland most shipable cultivars of red and black plums

Basically some species inhibit the development of pollen tubes forming when pollenated by pollen they recognize to be their own. Some just slow it down so it gets out competed by pollen from other plants, but if no other pollen is available the slowed down pollen tubes will still eventually have some success as a back up plan. Others inhibit the development of their own completely and simply won’t set fruit/seeds without cross pollination. There are other variables as well, but that’s the basic story.

Most apples fall into the category of discriminating against their own pollen, but there are examples of some varieties lacking this characteristic and allowing self pollination.