Triploid Fruit Trees

[FB.]

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When triploid is mentioned, it brings visions of large, vigorous trees which require two other trees for good pollination. Well-known triploids include Bramley, Blenheim Orange and the pears Catillac and Vicar of Winkfield.

For those who are unfamiliar with the term triploid and its implications, a simplification would be that the “mother” divides its genetic material by half and then gives one of those genetic halves to an offspring, with the other half of the offsprings genetic material being contributed by the “father”. With fruit trees, the “mother” would be the flower and the “father” would be the pollen grain from another tree, carried by a bee, to the flower. Apples and pears have 34 chromosomes, arranged into 17 pairs, with one of each pair being contributed by each parent.

Triploids arise when the mother or father’s genetic material is not divided into two, such that the mother might provide all its genetic material to the offspring, plus the father adds its share. This results in 34 chromosomes from the mother and an additional 17 chromosomes from the father. The result being a triploid – with three copies of each of the 17 chromosomes.
Having three of each chromosome (3x 17 sets = 51 in total), triploids can't divide the uneven number into two halves of 17 chromosomes when their pollen is produced, with the result that almost all their pollen grains have genetic abnormalities and therefore usually not very viable - the pollen is mostly sterile, so to speak.

Occasionally, the offspring might have all 34 from its mother and all 34 from its father, which would result in a tetraploid – with four copies of each of the 17 chromsomes.
Very occasionally, a chromosome gets “lost”, or copied, or unevenly divided during reproduction, resulting in an offspring with, say 17+1 chromosomes from one parent and the usual 17 from the other parent. This makes an aneuploid, which often is not a viable seed, but a few are capable of a relatively normal life. An example of this in humans is three copies of chromosome number 21 and two copies of all the others, which we all know as “Down’s Syndrome” (“trisomy 21”).

When browsing nursery catalogues, it is assumed that the nursery has conveniently labelled all the triploids, so that we might be able to meet the triploids' requirements for additional room to grow and for additional pollinators.

However, it is my belief that there are many more triploid fruit varieties than we are told. The reason being that there simply hasn’t been thorough enough research to identify all the triploids. The commercial orchards frankly don’t care about old, rare varieties, so why would anyone have bothered to do a detailed genetic analysis?
It is also my belief that there are some polyploid varieties (several sets of chromosomes) and also some aneuploid varieties (which have additional chromosomes but not meeting a precise pairing number 2x=diploid, 3x=triploid, 4x=tetraploid, 2x+1 would be aneuploid).

Having studied fruit trees intensively for a number of years, I have noticed – and heard from others – that triploids (or others with unusual chromosome numbers such as aneuploids) often show multiple unusual features, such as:

Vigorous growth.
Large fruits.
Large blossoms (often very attractive).
Large leaves.
Thick, stiff, leathery leaves.
Unusually dark-coloured leaves.
Unusual-shaped leaves, such as relatively rounded shapes.
Distorted leaf shape, such as off-centre leaf tips, crimped or partially folded leaves.
Low seed count, or deformed-looking seeds.

Not all of these features are evident in all cases.


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Additionally, triploids tend to show the following features:

More disease resistance (due to more genetic material which may contain resistance genes).*
Better tolerance of difficult growing conditions (due to extra vigour and disease resistance).
Erratic cropping (due to the need for good pollination from a diploid variety).
Tendencies for fruit disorders such as bitter pit (due to poor seed content of the fruit; good seeds promote good fruit).

*
The usually-greater disease resistance of triploids can still be overcome by diseases if the variety is/was grown so widely that the diseases are/were forced to evolve to live on it or risk becoming extinct. Bramley was once highly resistant, but, having been grown for two centuries, the diseases are now getting well-adapted to attack it, with the result that Bramley's disease resistance is only about average nowadays.

Tetraploids, being able to divide their genetic material equally, tend not to have the fruiting or fertility problems associated with triploids, but tetraploids may still show many of the features such as large leaves and blossoms.


Over the years, I have grown or observed a number of varieties. Based on my observations, I would suggest their genetic constitution is as follows:

“Normal” diploids and “fertile” others, such as tetraploids:
Beauty of Bath: diploid (2x)
Crawley Beauty: diploid (2x)
Tydeman’s Late Orange: diploid (2x)
Spartan: diploid (2x)
Court Pendu Plat: diploid (2x)
Discovery: diploid (2x)
Bountiful: diploid (2x)
Laxton’s Superb: diploid (2x)
Red Devil: diploid (2x)
Ellison’s Orange: diploid (2x)
Scrumptious: diploid (2x)
Fiesta/Red Pippin: diploid (2x)
Egremont Russet: diploid (2x)
Golden Delicious: diploid (2x)
Cox's Orange Pippin: diploid (2x)
Charles Ross: diploid (2x)
Worcester Pearmain: diploid (2x)
James Grieve: diploid (2x)
Lord Lambourne: diploid (2x)
Laxton’s Epicure: tetraploid (4x)
Winter Majetin: tetraploid (4x)


“Abnormal” triploids and aneuploids:
Belle de Boskoop: triploid (3x)
Jupiter: triploid (3x)
Gasoyne’s Scarlet: triploid (3x)
Hambledon Deux Ans: triploid (3x)
Coeur de Boeuf: triploid (3x)
Edward VII: triploid (3x) or aneuploid
D’Arcy Spice: aneuploid
Norfolk Beefing: triploid (3x)
Blenheim Orange: triploid (3x)
Bramley: triploid (3x)
Alfriston: triploid (3x)
Ashmead’s Kernel: triploid (3x)
Annie Elizabeth: triploid (3x) or aneuploid
Jumbo: triploid (3x)
Suntan: triploid (3x)



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Please bear in mind that the above is WHAT I THINK. I might be wrong – and what I have written is certain to have its disbelievers and critics.

I hope that's of interest.

[Speed Gardener]

FB - we are not worthy!!!

[yummersetter]

See how far I've got through the archives!

This is really a fascinating posting. The whole field of genetic differences in apples is so interesting.
I have dozens of unusual varieties of apples and suspect that several are unrecorded triploids. This year, being a bad year for fruit, seems to be a great year for foliage and I'm considering making a set of photos of each variety's leaves, I've never seen them look so healthy at this time of year. The puzzle is that on each branch there are differing sizes and shapes - when you photographed yours did you just go for the average / majority?

I guess that any day now we'll be sending bits of apple to Brogdale for a genetic ID, rather than counting the notches round a leaf edge.

[orangepippin]

FB's informed guess (last year) that Ashmead's Kernel was a triploid was recently confirmed in a scientific paper published by Defra.

[yummersetter]

Hello, OP! Yes, A'sK and Suntan were the eyebrow-raisers for me on that list. And to know that there were such weird things as aneuploids, I need to learn more about this.
I think in our old orchard a lot of the ancient survivors are triploids, almost by definition, so I had to think what to put where and why when I replanted.

[yummersetter]

I've just found the DEFRA DNA tested triploid list from a link on your website, Orange Pippin, extraordinary! A lot of my triploid spotting by leaf this morning confirmed, Morgan Sweet, Orleans Reinette and Tom Putt, the Golden Russett isn't at Brogdale and the others were known triploids when I planted them. It's a nuisance that quite a few of the diploids I've planted are biennial, as now I see that they're carrying more of the pollination load than I intended.

[orangepippin]

Suntan is listed in the excellent Hessayon Fruit Expert book as a triploid.

[FB.]

Suntan is listed in the excellent Hessayon Fruit Expert book as a triploid.

Yes, Suntan is triploid.
Cox contributed two sets of chromosomes and Court Pendu Plat contributed one.

Suntan has thick shoots like a Bramley.

I found Suntan to be hopelessly prone to powdery mildew - then the MM106 rootstock began to die from crown rot, so I removed the tree.

I can't say that I'm a fan of Hessayon. The book is OK as a starter, but I think that Hessayon has an obsession with "spray, spray and spray some more" and also lacks an appreciation of the way different varieties, soils and climates interact.
The book also writes off vigorous rootstocks as "too big" (not true in many dry, chalky Eastern areas when unsprayed!) and only discusses common and popular varieties - failing to mention many of the excellent old varieties.

[FB.]

It's a nuisance that quite a few of the diploids I've planted are biennial

I've been wondering whether diploids may generally be more biennnial because they tend to produce more and larger seeds. Seeds are far more of a drain on the tree than the fruit flesh, so a fertile diploid may well put so much effort into the pips in one season that it has to have a year off to recover.

Triploids, with their lower fertility and tendency to produce fewer but larger fruits and with sparse/absent/deformed/stunted pips therefore seem likely to not be exhausting themselves and the soil. Perhaps this tendency to not deplete the soil of nutrients so quickly is what gives triploids and edge in longevity and adds an additional boost to disease resistance due to the soil being less drained of nutrients.
Presumably the lower nutrient requirements of triploid fruits (due to lower quality seed) also allow the triploid somewhat more resources for extra growth each year, in addition to fruiting. Perhaps this goes part way to explaining the tendency for triploids to be larger trees, whereas the fertile diploids and tetraploids are more nutrient-hungry due to greater viable seed count.

For example, the very fertile diploids "Beauty of Bath" and "Spartan" are known for being quite hungry plants, with a reputation requiring heavy quantities of potassium in order to remain productive. This is, no doubt, due to high fertility causing lots of pips which need lots of feeding.
For me, most diploids are completely biennial: heavy crop of small fruit in one year, then no crop at all the next year.

[orangepippin]

I can't say that I'm a fan of Hessayon. The book is OK as a starter, but I think that Hessayon has an obsession with "spray, spray and spray some more" and also lacks an appreciation of the way different varieties, soils and climates interact.
The book also writes off vigorous rootstocks as "too big" (not true in many dry, chalky Eastern areas when unsprayed!) and only discusses common and popular varieties - failing to mention many of the excellent old varieties.

It's very much a book of its times, i.e the previous century. p50 (in my copy) has a spraying programme (which is basically spray, spray, spray). It was the first fruit book I purchased, and for such a small book I think it really packs in an amazing amount of detail, and covers, albeit fleetingly, almost every aspect of fruit-growing. I only recently noticed that its apple catalogue even includes a colour shade to aid identification.

I think a copy of this, along with the Michael Phillips Apple Grower (which is completely organic) and the RHS pruning and training guide will take you a long way in top-fruit growing.

[FB.]

I think a copy of this, along with the Michael Phillips Apple Grower (which is completely organic) and the RHS pruning and training guide will take you a long way in top-fruit growing.

I think using forum boards such as this to talk to experienced growers in your local area goes even further!

[yummersetter]

I planted the Suntan 22 years ago so may have known it was a triploid and forgotten. The number of triploids around it might excuse, but it's been disappointing, very few flowers for about 12 years, never really had more than a minor crop and they're not memorable apples. No disease problems though.
There are a score or so diploid trees in the same acre but the one which seems most vital is the James Grieve. When that doesn't flower, or is affected by bad weather, we get poor fruit set in about 8 surrounding trees.

[FB.]

the one which seems most vital is the James Grieve. When that doesn't flower, or is affected by bad weather, we get poor fruit set in about 8 surrounding trees.

I think that humans have inadvertently selected many old varieties which happen to be triploid. I therefore think that the reports of "erratic cropping" are because people are planting a known triploid, then trying to pollinate with a variety which is assumed to be diploid but is actually also triploid or aneuploid. Pollination is therefore poor unless bees happen to bring in pollen from elsewhere - and this bringing-in of pollen will be random and variable - hence the "erratic" cropping often reported in triploids and certain other varieties.

I think that in many apple collections, just one or two trees do all the pollinating - and when those key varieties aren't flowering, the whole orchard's crop is affected.

Another thing regarding pollen:
Not all varieties produce as much good pollen as others, and even if they do produce lots of viable pollen, they will not be good pollinators for varieties to which they are closely related.

While on the subject of James Grieve: I'm surprised that you've managed to keep James Grieve going in your relatively damp climate - I'm in a relatively dry area, but in this abnormally cold, dull, wet spring I lost my James Grieve (and Egremont Russet) to a sudden and massive attack of canker. My other varieties being completely unaffected.

[FB.]

When it comes to pollinators, I would be especially cautious of the ancient varieties which have been handed-down through the generations (e.g. Ashmead's Kernel c1700, Coeur de Boeuf c1200, Norfolk Beefing c1600, Ribston Pippin c1700). I think that a very large proportion of those ancient varieties have survived through the ages because they are resilient triploids (or aneuploid) and as a consequence are therefore of dubious value as a pollinator.

Some varieties which I would shortlist as useful pollinators, subject to having enough disease resistance for certain areas (even some of these may turn out to be triploid or aneuploid, so I take no responsibility for anyone using the list below!):

It must be remembered that related varieties will often be poor pollinators

All the following should be good pollinators, but it does depend somewhat on the variety they're trying to pollinate and how closely related they are.

So I'll make three groups:

1. Varieties very likely to be a satisfactory to excellent pollinator for almost every variety:

Beauty of Bath 1,4
Tydeman's Early Worcester 24,25
Discovery 1,24
James Grieve 8,9
Worcester Pearmain 2,24


2.
Varieties likely to be a satisfactory pollinator for most varieties.

Ellison's Orange 1,5 (Biennial)
Braeburn 9,24
Irish Peach 1,1
Jonathan 7,9
Katy (Katya) 5,24
Spartan 9,10 (Biennial)
Laxton's Superb 5,16 (Biennial)
Tydeman's Late Orange 9,16 (Biennial)


3.
Varieties which can be good pollinators, but which are part of large "families" bred from the same variety and where incompatibility problems may occur:

Falstaff (and all Falstaff variants) 2,5
Fiesta 3,5 (Biennial)
Gala 2,5
Greensleeves 2,5
Golden Delicious 2,3
Kidd's Orange Red 5,9
Lord Lambourne 2,5




If I had to choose a few varieties to meet the need for "this one tree is not particularly prone to disease and is a compatible partner for as many varieties as possible and isn't too prone to biennial flowering", it'd probably be:
Tydeman's Early Worcester, Discovery, or Beauty of Bath.

[yummersetter]

Well, I've done a back of envelope head count and in the old orchard there are 18 triploids and 19 diploids, plus 6 unknown of which I reckon 3 are triploid. I replanted about 20 trees in the 1990s, the rest are antiques. Of the diploids only 4 are totally biennial, but some of the others are Cox and offspring. I didn't know 4 of the replants were triploids, or that 60% of the old trees were. I did plant Blenheim, Egremont Russet and Jupiter knowingly and with pollinators alongside, mainly a huge old Beauty of Bath.
The James Grieve is the last survivor of 3 planted in the 1920s and doesn't have much canker though it would be hard to spot small amounts through the lichens, maybe they're a barrier. On the other two the trunk bark rotted away on the northern side. I'm hoping prevailing winds will keep your canker blowing into the North Sea, not towards the west

edited to correct 'I did plant Blenheim, Egremont Russet and Jupiter ' to 'Blenheim, Ribston Pippin and Jupiter' Slap fingers!