Schoener's rose-apple, Schoener's Nutkana

[Karl_K]

[quote=ldavis]

There is no doubt that methylation and acetylation of chromosomes is happening all the time to control gene expression. That’s how plants know it is winter, or spring. There is also imprinting from the parent during reproduction. And much as we might like to resist it, there is evidence that there is inheritance of the effect for one or more generations for some of the DNA methylation patterns. These all go under the title of epigenetic, a huge catch-all term for anything that isn’t the classic DNA-> RNA-> protein kind of genetics. [/quote]

I have an article (on my home computer; I’m on the road at present) about a “vernalization gene” in carrots that determines whether a given plant is annual or bienniel. It occurred to me that carrots migrating from place to place could benefit by adaptively (and epigenetically) altering the state of such a gene rather than discarding it (the archaic presence/absence model). In this way a population that finds itself growing in poor soil could become bienniel, and gain an extra season of growth to store nutrients for seed production. Then, when descendants arrive in more favorable conditions, they (or some of them) could revert to the annual growth habit.

The “trick” in growing carrots is to maintain the “I’m growing in poor soil and must be bienniel” character of the plants, while also providing deep, rich soil that favors the largest and sweetest roots. Even so, garden carrots do give rise to the occasional wildling.

The same model could account for DeVries’ inability to persuade his Oenothera Lamarckiana strain to become reliably annual. Every year a few of his plants “sported” to the bienniel habit, and were promptly removed.

The easy conversion of winter wheat to spring wheat (and vice versa) is another example that makes sense when we think of a species migrating from region to region. Epigenetic conversion of some “vernalization gene” would be a more reasonable model than assuming that a new “gene mutation” must occur every time the population finds itself in a different habitat.

I would not call Daniel’s work “hogwash” because I have read more about it. He experimented on a wide range of plants, but was attacked for reasons that bordered on the political. He found, for example, that French grapes grafted to roots of American types were not merely resistant to blight. Other qualities were altered, as well. This did not please some growers (the “Americanists”) who refused to believe (despite taste tests) that wine from grafted vines was inferior to the own-root types. They and their allies put the squeeze on Daniel, curtailing his research.

I do have a bibliography of Daniel’s writings, and writings about him.

Karl

[Karl_K]

Here’s another example of the (sometimes) benefit of grafting before crossing:

"From the crossing of the wild potato species Akaule (Solanum acaule) Bitter with cultivated varieties hybrids rarely result, and when they do they are of wild appearance and produce hardly any tubers. Such hybrids have to be pollinated repeatedly for several generations with the pollen of cultivated varieties, i.e., they have to be impregnated all the time with a cultivated variety. Only after that is done can a variety with cultivated characters be obtained. Of course, some of the wild plant’s good properties, for the sake of which it was taken for crossing, are in many cases entirely lost in the process.

“A. S. Filippov, a young Soviet scientist at the Potato Institute, tackled the problem of crossing distantly?related forms of potatoes in the Michurin manner. He grafted a plant of the wild potato species on to a cultivated variety (the Michurin method of approximation). When flowers appeared on the wild scion he pollinated them with the pollen of the cultivated variety. In the very first generation (i.e., after a single crossing between the wild and the cultivated species) a cultivated type appeared, at all events, one much more cultivated than the plants growing next to it of the same wild species, which for three consecutive generations had been pollinated with the pollen of cultivated varieties.”

Karl

[Don]

Karl, since you’re dredging up the work of long dead Lysenkoists you would do the youngsters here a service to frame Michurin and Filippov in their (ahem) historical perspective.

Actually, I was interested to see that there is (or was recently) an Alexis V. Filippov engaged in Solanum research at the Russian Agricultural Academy - probably no coincidence.

[ldavis]

Just to stir the pot a little, let’s acknowledge that Darwin believed in inheritance of acquired traits and even discussed how they got transferred to the gametes. Later Lamarck went into eclipse and Darwin was “cleaned up” by the Mendelians. Now we are finally, after some decades of very strong resistance, recognizing that there are in fact epigenetic traits, which means they are responsive to modifications of the "arrangement " of DNA and its decodability. Some such traits continue from one generation to the next. We’re not far enough along in studies of these to know whether any such changes are essentially permanent, or only last one or a few years (or cycles of DNA replication, whichever comes first).

RNA editing is another really weird phenomenon common in plant mitochondria. In that case the DNA sequence doesn’t mean what we think it does.

So while the historical context of Lysenkoists makes a lot of their work suspect for political reasons, some of it may turn out to be right. The problem is to sort out which parts are which. Unless their reports were followed up by published studies outside the FSU that affirmed or refuted their work, we have little to go on. Unfortunately most negatives don’t get reported except in small distribution newsletters, or at informal meetings.

When I first studied genetics I found it very hard to believe corn breeders who talked about how the cytoplasm affects the vigor of a cross, and the combining ability of a pollen parent. But of course now we know that there is DNA in mitochondria and plastids so the cytoplasm (maternal) does affect the cross. Then we have the rare genera in which the male, not the female, is the donor of mitochondria, or those in which there is a little of both, allowing for some complicated population genetic effects.

And as I mentioned up a few posts, there is definitely RNA floating round doing stuff. So why not across a graft, to interact in some still unknown ways with the scion/ stock interaction. Yes, it’s more likely that much of what was seen in the FSU 50 years ago was politically correct (for its time and place) wishful thinking but some of it might give us some useful hints for tests of our own. Look at Tom Silver’s Gapland Gold hybrid sunflower/ Jerusalem artichoke. He was inspired to make such a wide cross by a very interesting paper on Karl’s site, where a Russian scientist had done the equivalent wide cross and reported in considerable detail on the results.

We have no problem believing in plant hormones which are small and well-documented. But now we have florigen, a good sized protein as a migrating hormone. And mobile bits of RNA. Who know what next.

[Don]

I enjoy reading Karl’s posts and appreciate the availability of the material he posts on Bulb n Rose. I do generally remain very, very skeptical of anecdotal reports of epigenetic events especially ones that originated in the Soviet period.

I also think that the half century of terror instigated by Lysenko should not be forgotten. Most of the readers of this forum have no idea that some of the quaint and quirky stories have a curtain of blood as a backdrop.

[ldavis]

I don’t mean to minimize the Lysenko tragedy at all. But I’ll try to get a paper together for the winter newsletter that shows that epigenetics (of some kinds) is rock solid, and in fact DNA methylation and acetylation is how the plant maintains its memory of winter. Also that RNAi is all around us. Anecdotes are anecdotes, I figure. Some fraction might have some truth in them. If only we knew which.

[Karl_K]

In regards to the “tragedy” of Lysenko and his colleagues, it is worth noting that the field of genetics was dominated by eugenicists in the first half of the 20th century. They adopted Mendel as their patron saint, in opposition to Darwin’s theory of evolution by natural selection. Thomas Hunt Morgan even went so far as to rewrite Darwin, bringing him into line with the racist/classist beliefs of the period. (Morgan was born and raised in the home of his uncle, Gen. John Hunt Morgan, the Thunderbolt of the Confederacy. Racism begins at home.)

Lysenko denounced eugenics as the fascist distortion of genetics in the service of Goebels, which made him no friends among the racist/classist geneticists of the period.

When reading the numerous assaults against Lysenko, one striking fact soon becomes apparent: Lysenko was almost never quoted directly. Instead, the assailants would mention this or that claim reported by journalists in popular publications. The same sort of thing was done to Burbank here in the U.S. For example, both Burbank and Lysenko were accused of trying to breed bananas for the far north. Neither ever tried such a thing.

So far as I have learned, Lysenko (1928) was the first to identify plants whose flowering depended on both vernalization AND photoperiod. He also recognized other plants whose time of flowering was influenced by heat. Thus, he was able to sort out the inheritance of flowering time in wheat – a problem the Mendelianists could not handle.

I am not aware of any “half century of terror instigated by Lysenko”. The eugenicists/mendelists screamed bloody murder when they were challenged in any way, strangely accusing Lysenko of “suppressing” them. They believed, incorrectly, that prolonged inbreeding of corn (maize) would eventually produce inbred strains that could be crossed to produce high-yielding hybrids. When they failed, they blamed Lysenko, who had done nothing to hinder their wasted efforts. Meanwhile, Lysenko reported that other Soviet corn breeders had produced very useful results by crossing ultra-early strains with the higher-ylelding but late strains. Heresy! Please note, that in the same period Edgar Anderson in the U.S. was sorting out the basic fact that hybrid vigor in American corn originally resulted from crossing of the early and ultra-early Northern Flints with the late Southern Dents. Anderson was too well known and too respected to be denounced as a heretic like Lysenko even though he refused to join the “Modern Synthesis” gang.

And as for Lysenko’s alleged attack on Mendel, Donald Forsha Jones (1928) was tougher on the mendelianists than Lysenko was: "And even when deficient or excessive ratios are obtained, they have been obscured by the prevalent practice of compiling data from many individuals of different pedigree and in successive generations in order to obtain as large numbers as possible. This procedure serves its purpose well. The thoroughgoing Mendelianist seldom fails to obtain ‘very good ratios.’ "

Please do not confuse Lysenko with Stalin. I cannot comment on the politics of the time, but Lysenko and Gluschenko, among others, condemned racism in the U.S., while American mendelianists/eugenicists ignored lynchings. Opposition to lynchings was regarded at the time as indicating communist tendencies. And it was not Lysenko who instigated forced sterilization in the U.S., or looked on approvingly when the practice spread to Germany.

I would check the credentials of any author who attacked Lysenko. If he/she was a card-carrying Eugenicist, beware of the lies.

Karl