Memory stress test

Or should I say Stress Memory Test?

Researchers Surprised After They Graft Tomato Plants With Epigenetically-Modified Rootstock

At first read this article seemed like a flashback to Lyshenko’s vernalization experiments but, no, there is actually a modern scientist risking his professional reputation by studying the inheritance of acquired characteristics.

The scientist is Michael Axtel from Penn State and he studies small RNA’s.

So, will we eventually be able to buy a bottle of ‘Stress sRNA’ to spray on our roses instead of moldicide?

Epigenetics seems to be mostly accepted science now?

I was wondering if you could produce an epigenetic blue rose by keeping it under different light conditions?

Or maybe it is high levels of ultraviolet light that causes flowers to be blue, as many naturally blue flowers seem to grow at high altitude, such as the Blue Himalayan Poppy and Alpine Gentians. Ultraviolet light is damaging and all those coloured substances like carotenes and anthocyanins (and delphinidin?) are produced by plants to protect them from ultraviolet light. Maybe blue flowers are more protective against ultraviolet (and blue?) light?

If native blue flowers are more common at high altitudes, I wonder if this happened due to natural selection and survival of the fittest, or if there is an epigenetic factor? It probably took millions of years?

OK, would this mean that budding rose scions to stocks raised in Wasco, where it’s hotter than a two dollar pistol, might have been creating rose plants more able to adapt to prolonged higher heat?

[quote=julie777 post_id=72232 time=1603398490 user_id=2252]
Epigenetics seems to be mostly accepted science now?[/quote]

Yes, we covered it in our graduate courses for plant genetics in 2018 so it’s safe to say it’s quite accepted at the academic level. There have been some interesting studies, but we did not hit on a lot that was pragmatically applicable. However, epigenetics can be used in long term breeding programs. It has been shown to be heritable which is good for widening the selection pool in selections with low genetic variance. It is also good for upregulating or downregulating already known traits.However, the heritability is not generally high, but it is significant enough to be used in large programs.

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I first read about Lysenko around 1977. I was working part time in the library at K-State, and handling many books I might never have seen otherwise. Good times! So I read a bit about Lysenko, along with some of his colleagues. I read a good deal of C. D. Darlington, before I learned what a racist he was, and a hypocrite for supporting the bizarre notion that social classes have their roots in genetics. Darlington was reportedly born into the poorest of poor. I’m thinking Onslo and Daisy on Keeping up Appearances. I also had the very good fortune to encounter some splendid researchers associated with the USDA in the late 19th and early 20th centuries.

The more I learned about Lysenko, the more clearly I saw how some of his critics resorted to blatant lies to smear his name. The man was not an ignorant peasant, as some (especially in England) would claim. Funny how these same people carefully ignored that Mendel was also the son of peasant farmers. And the dangerous fact that Nils, a Swedish peasant boy with no surname, would have a son who became Sir Carl von Linne. That’s a pretty quick progression from peasant to nobleman. I think Darlington would have trouble explaining in genetic terms.

But coming back to the subject at hand, I have some examples of characters apparently being acquired at some time, them being lost when environmental conditions change.

Allen (1898)

A number of years ago I brought from Stanstead, in the Province of Quebec, a few ears of corn which ripened there, in a climate where there was not a month in a year without frost. This corn did not grow more than four feet high, yet each stalk produced two small but perfect ears of sound yellow corn, in the six weeks it had to perfect its growth. This corn was planted on the east shore of Cayuga Lake, and astonished the grower by reproducing itself by the 1st of August. He thought his fortune made, and he planted all the product the next year for seed purposes. But his early corn was no longer early; finding it had four months, instead of six weeks to do its work, it took all the time, and the farmer had a fine crop of yellow eight-rowed corn, the same as is now generally grown in the northern part of the State.

Tracey (1904)

Speaking first of leguminous plants, in the ‘Extra Early’ varieties of garden peas the desirable form of vine is one eighteen to forty inches high, and of a determinate growth, by which term I mean a vine that before the lowest and first formed pod has become too large for use as green peas, has completed its elongation and has its apex crowned by a well-formed pod or at least one well out of the blossom. The objectionable form is a vine twenty-four to sixty inches in height, which even when the lowest pod is fully ripe is still growing having its apex covered with blossoms and buds. Such plants as these last are called by seedmen ‘wicks’ or ‘offs,’ and a stock of ‘Extra Early’ peas is valued in inverse proportion to the number of such plants it produces. I never have seen a stock which did not occasionally produce them, and in number varying with different conditions of cultivation. On very rich soils, or those which have been recently fertilized with stable manure, there will be a great many more such plants developed than on a poorer soil. A stock which, when grown on a white clay soil of uniform composition, will ripen down very uniformly and not show more than a dozen such ‘offs’ to the acre, will, when planted on a mucky soil or one which has been enriched by fresh stable manure, give a dozen ‘offs’ to the square rod.

As an illustration in detail is a case when three large fields of very favorable soil were planted with the same stock, two of them when visited showed practically no ‘offs,’ nor were there many to be seen in the third field, except in a double row of circles, each about ten feet in diameter, where piles of manure had been spread, and in each of them there were twelve to twenty-five bad ‘offs’ more than could be found on an acre of the rest of the field.

Seedsmen find that if the seed from such ‘off’ plants grown from good stock is planted on soils favorable for the development of the true type, it will produce few, very few, often no more ‘off’ plants than seed from plants of the true type grown from the same stock; but if seed from the ‘off’ plants is sown on soil favorable for the development of ‘off’ plants, they will produce more ‘offs’ than seeds from the true type, and this tendency to produce ‘off’ plants on either favorable or unfavorable soil increases very rapidly with the number of consecutive generations of ‘off’ plants back of the seed in question. An illustration was given of precisely similar results with ‘American Wonder’ peas when the character of soil favorable for the most desirable type is the opposite of that favorable for the best ‘Extra Earlies.’

Winter-flowering Sweet Peas (1907)

Mr. Svolanek states that he finds it necessary each year to grow his stock seed under glass, as in the beginning, because the varieties quickly revert to the ordinary type of spring-flowering Peas if not so handled.

I forgot to add a link to my bibliography on the subject.

Graft transmission is related, but I have a separate bibliography for it.

And a bibliography of Epigenetics and related matters.

It might be time to re-examine some facts that were already established in the early 19th century. For instance, William Prince, the once-famous nurseryman of Long Island, NY, reported (1832) an important observation:

I have now to state to you what I have never met with in any author, that the graft has an influence on the stock and root of the tree. The cherry tree when the thermometer in hard winters falls much below zero, is frequently killed by the severity of the frost. I had some years ago, 1821, a number of cherry trees killed, but the Weeping cherry, a native of Siberia, although budded some height from the ground, remained uninjured; this led me more minutely to examine their roots, and I found invariably, that the roots of all the weeping cherries differed from the roots of other cherry trees, although the stock was the same; the roots of the trees grafted or budded with the weeping cherry being much fuller of fine spreading fibres, and rooting much stronger. Mentioning this fact to a man who keeps a small apple nursery in this place, and on whose veracity I could depend, he told me that the graft of the Siberian crab apple trees, although grafted two feet from the ground, affected the roots, and caused them to become so wiry and hard, and so full of these fine tough fibrous roots, and that they were very different from the roots of other apple trees.

Subsequent reports agreed that the scion-stock influence was most effective with the seedling stocks were one or two years old. Beyond that, they were “set in their ways”.

In a side-note, Prince wrote, “In France they formerly used to graft the same sort over and over again three or four times on the same stock.”

However, this technique was intended to alter the graft, rather than the root.

Scion-Stock influence also has been reported in Roses.

Michurin: Influence of the scion on the structure of the root system of the stock (1916)
Several strains of roses were grafted on a bed of wildlings of the Rosa canina. Among them was a new Rosa lutea hybrid [Kazanlik x Persian Yellow] which I bred. Three years after the grafting all the roses from this bed were dug up for transplantation, and it turned out that, with few exceptions, all the specimens of the grafted Rosa lutea [hybrid] had absolutely smooth roots, without any branchings and fibrils as is usually the case with the Rosa lutea on its own roots. At the same time all the grafts of the other strains had a well-branched and fibrillous root system. Of course, such an example of particularly strong influence of a scion on a stock is an exception. Nevertheless, it is a fact, and horticulturists must bear this phenomenon in mind. Even though it may manifest itself in other plants in a lesser degree, but manifest itself it will all the same.

Some of the “geneticists” (or fruitfly breeders) seemed to consider organisms to be collections of traits. They held a static view of the subjects, mostly ignoring the developmental processes that made a completed plant or animal from a fertilized egg.

This developmental program is too easily ignored. For example, De Vries (1906):

The common cockscomb or > Celosia cristata, > one of the oldest and most widely cultivated fasciated varieties may be used to illustrate the first point. In beds it is often to be seen in quite uniform lots of large and beautiful crests, but this uniformity is only secured by careful culture and selection of the best individuals. In experimental trials such selection must be avoided, and in doing so a wide range of variability at once shows itself. Tall, branched stems with fan-shaped tops arise, constituting a series of steps towards complete atavism. This last however, is not to be reached easily. It often requires several successive generations grown from seed collected from the most atavistic specimens. And even such selected strains are always reverting to the crested type. There is no transgression, no springing over into a purely atavistic form, such as may be supposed to have once been the ancestor of the present cockscomb. The variety includes crests and atavists, and may be perpetuated from both. Obviously every gardener would select the seeds of the brightest crests, but with care the full crests may be recovered, even from the worst reversionists in two or three generations. It is a double race of quite the same constitution as the twisted teasels.

De Vries seems not to have noticed that what he observed was variation in the age of onset of fasciation. That is, there is no “unit character” distinguishing the large, solitary crest of the florist’s specimen from the small bits of fasciation at the tips of the inflorescence.

There are some useful examples of plants correcting their developmental programs when they have been disrupted by mutations, hybridizations, chromosome doublings, and some environmental anomalies. Fagerlind (1958) was working with Rose polyploids, but also gave some helpful examples from other families.

B. The literature contains a few descriptions of phenomena which in a way seem to constitute parallels to the demonstrated > rugosa > doublings of which an account has been given above. SCHLÖSSER (1934) speaks of a gradual, time-consuming stabilization in a 52-chromosome clone of tomatoes. The clone derived from a newly formed (4n+4)-plant among 4n-siblings. This diverged from its sisters in a striking way. The latter showed normal fruit-forming properties. The diverging plant shed its flower-buds when these had attained an approximate length of 3 mm. It was reproduced by means of top-cutting for 9 generations. Each generation required a period of 2.5-3 months. With each generation the bud-shedding tendency was reduced. In the fourth generation, “kam es fast zur Anthese bei einigen Knospen, doch wurden sie aus inneren Gründen im letzten Augenblick abgestossen”. [> it came nearly to the anthesis with some buds, but from internal reasons in the last instant it was pushed off.> ] In the sixth generation fully developed flowers appeared. In the fifth generation the buds contained lethal pollen in 80 per cent of the cases, but in the seventh the figure had sunk to 35 per cent, a feature thought to be due to changed chromosome distribution during the meiosis. The majority of PMC were believed to distribute the chromosomes in such a way that 24 went to the one and 24 to the other pole, while the 4 surplus ones remained lying in the plane of division. In the ninth generation fructification occurred. The fruits often showed a normal amount of seed. The F1-plants that were pulled up proved to be tetraploid. Control analysis showed that the members of the clonic chain of generations had the whole time possessed the chromosome number (4n+4).

The idea that a series of random gene mutations could just happen to occur as needed to correct the chromosomal imbalance is just too silly to entertain. The plant experienced a small genomic shock each time it tried to flower but failed. And each little shock allowed another readjustment.