Fruit Tree Pollination

Hey folks,

Can someone explain to me how it is that some trees need cultivars of other trees to pollinate? That makes very little sense to me as a necessity scientifically speaking. I'm looking at making a native plant orchard, which would include a Malus Fusca. Considering it is the only native apple to my region, I highly doubt that it needs to cross-pollinate with another Malus that is not native to its region. This is true for other fruiting trees of the region as well. Can someone rectify these two truths for me? (Truth 1: Apple trees need cross pollination with other cultivars. Truth 2: This apple tree is the only native apple tree.)

Thanks!

Many plants have a genetic mechanism which prevents self-pollination. It is called "Self-incompatibility". The way it typically works is that there is a collection of genes, for purposes of this example, we'll call them the S gene. But there isn't just one S gene in the species, there are a bunch of them, so there will be s1, s2, s3, s4, s5, s6, s7, s8, s9, etc...  So if the apple tree that I planted has the s5 gene, then it can be pollinated by pollen that carries any of the S genes other than s5.

Malus fusca is a species of apple. If it needs a pollinator, then within that species, there are many different S genes. You'd just need to plant two trees with different sets of S genes... (Presuming that it's a species that  needs a pollen donor.) Random chance offers a pretty good opportunity that two trees will have different S genes. When I sell tomatillo plants, which are also self-incompatible, I typically include 3 plants in the pot, for good measure.

Joseph Lofthouse wrote:Many plants have a genetic mechanism which prevents self-pollination. It is called "Self-incompatibility". The way it typically works is that there is a collection of genes, for purposes of this example, we'll call them the S gene. But there isn't just one S gene in the species, there are a bunch of them, so there will be s1, s2, s3, s4, s5, s6, s7, s8, s9, etc...  So if the apple tree that I planted has the s5 gene, then it can be pollinated by pollen that carries any of the S genes other than s5.

Thanks for the answer. So, for clarity, when we say "self-incompatibility" we mean ANY of the same "s5" plants, not just a different flower of the same tree? And is there somewhere that has a documented list of these genes?

Would I be correct to assume then, that either Malus Fusca can pollinate with itself OR there is another plant in the wild it pollinates with that is not an apple. Considering that there is no other native apple.

All Malus fusca trees are crab apples. The species pollinates just fine within itself, however, if the species is self-incompatible, then a single plant of that species cannot pollinate itself. There will also be subsets of the species which cannot pollinate other plants within the species because they have the same S genes.

I'm a pragmatic farmer and plant breeder... It's impossible for me to do genetic testing on the plants that I buy and grow. Therefore, if a species has a reputation for being self-incompatible, then I plant multiple unrelated plants instead of one. Or I graft unrelated scions onto the same root-stock. If you are buying Malus fusca from a reputable nursery, they will know about self-incompatibility. If you are growing multiple plants from seeds, then you probably don't need to worry about it.

Malus fusca is a species not a cultivar
So in general any wild or even named cultivars of Malus fusca will polinate your native apple, in fact even most species in the Malus genus will pollinate your apple.

Check out this website for a list of fruit tree and pollination requirement. https://onegreenworld.com