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Old 05-22-2020, 09:29 AM
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Why citrus seeds from grafted citrus come true but Apples won’t ?


Many citrus varieties (sweet oranges, key limes, grapefruit, tangerine and tangelo) when grown from fruit seeds, (from grafted plants) will come true (I.e. grow to give fruits of the original variety). Cite : https://chriscondello.wordpress.com/...y-store-fruit/

This never happens with other grafted fruit trees like apples, pears or stone fruit.

Can you please explain why ? Thanks
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Old 05-22-2020, 09:42 AM
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I think that article is somewhat misleading - it depends a lot on the variety.

Last edited by beowulff; 05-22-2020 at 09:43 AM.
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Old 05-22-2020, 09:43 AM
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That article goes into some detail about seed that's polyembryonic and thus supposedly producing offspring true to type, as opposed to monoembryonic.

Which is neat, and something I was unaware of, though there seems to be a long list of exceptions for citrus.

And of course, by not having a grafted tree you're doing without the benefits of the understock, which is typically hardier or more disease-resistant.

I understand that lemons are not dependable for seed producing the same variety characteristics. My only experience here is with Ponderosa lemons, whose seed-grown plants were loaded with thorns, much different-looking from the parent tree.
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Old 05-22-2020, 09:52 AM
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Beowulff and Jackmannii - agreed that the article I posted is not that scientific and there are lots of exceptions.

Even then the question still remains why some citrus are able to produce seeds (even when grafted) that produce true fruit plants ? Whereas this never happens with apples for example.
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Old 05-22-2020, 10:09 AM
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In general for fruits and vegetables, the answer probably lies in patterns of genetic inheritance involving particular dominant genes.

There seem to be a very few apples that will come true from seed, and it's said that peaches and apricots tend to produce identical or very similar offspring from seed/pits.
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Old 05-22-2020, 10:13 AM
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Grafting has nothing to do with it. The relevant thing is the genes of the scion, the bit that actually reproduces. The rootstock is a way of controlling the plant growth, it has no effect on the genetics of the next generation*.

I've actually heard that many citrus will produce very different fruit if grown from seed, because most of the fruit we eat are hybrids, propagated entirely by cuttings to ensure they stay the same between generations. Some, however, are species, and will stay true to type and some are natural hybrids which may have effectively formed a natural open pollinated variety... at least to a casual observer. These are the ones this guy's talking about.
I would hazard a guess that there's not as much genetic variation which affects fruit flavour and size within a citrus grouping as in many other fruits. How many different orange varieties are there? A dozen? How much variation within the taste? Many of the genes controlling things like sweetness are recessive as well, so if you're breeding within a variety, you're going to get that gene expressed in the next generation as well. Jumble the genes of a sweet orange's ancestry together, pick some out, and you'll probably get something pretty similar to what you started with. Probably not, in fact, quite the same, but close enough that you may not notice the difference.

With apples, on the other hand, there are literally thousands of cultivars; green, red, yellow, sizes vary enormously, and the flavours, including acidity, tannin, sweetness are pretty diverse as well. All of these cultivars have been propagated from cuttings since they were originally selected. If you jumbled up all the possible variations from a single apple's ancestry, then picked out a selection, the odds of you getting something pretty close to what you started with is tiny. Added to that, the odds are, your apple seed isn't all even bred from the one variety; many apple orchards use a few trees of a different cultivar, or a crab apple to ensure a good pollination level, because some apples are not self-fertile, and most crop better if cross-pollinated. This doesn't affect the apple, but it does affect the seeds.


*Yeah, yeah, maybe a teensy 'we don't fully understand it yet' epigenetic difference; for the purposes of this answer it's no difference.
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Old 05-22-2020, 05:42 PM
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I just recently learned that virtually all the citrus we are familiar with are quite complicated, genetically, deriving from many different interspecies hybrids.

Apples, in contrast are all selections of the same species, Malus domesticus.

It doesn't answer the question, but still interesting.
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Old 05-22-2020, 06:04 PM
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Quote:
Originally Posted by Ulfreida View Post
I just recently learned that virtually all the citrus we are familiar with are quite complicated, genetically, deriving from many different interspecies hybrids.
Yeah, I thought I understood lemon/lime, citron, grapefruit/pomelo, orange and tangerine to be the distinct species, but apparently it's way more complex and incestuous

Last edited by Mangetout; 05-22-2020 at 06:05 PM.
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Old 05-22-2020, 09:02 PM
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Apples don't propagate well from seed--they're highly variable even from the same apple. At least according to Michael Pollan, all those trees Johnny Appleseed planted by seed were for making hard cider, not for eating.
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