Research examines tomatoes but may have larger implications.
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Super interesting! I wonder what it would take what it takes to have that gene switched in the wild…
It is funny. My thinking on plants has been that they grow based on the amount of sunlight, water and nutrients available to them up to the point where the lack some critical nutrient or hit a maximum natural growth rate. If switching the gene expression to survival mode means that you get ~1/3 more apparent growth does that mean that that there is some aspect of plant physiology that is then not receiving resources or does the gene switching affect the plant’s “natural” maximum growth rate… If it is the latter that seems to imply the the plant’s normal gene expression for some reason is limiting growth… and that this seems weird… hmmmm…
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I didn’t read if they created the epigenetic change by chemical means or stressing the plants by heat or water stress.
If a plant grows well enough to reproduce then from an evolutionary viewpoint there is isn’t much need to do better. Selective breeding forces changes but is a slow process. Based on the article, epigenetics is a way to speed things up at least for vigor.
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You can trigger several changes in tomato plants with a few minor tweaks. My favorite two - because they increase fruit production - are to deliberately chill the plants in early spring and to deliberately water stress the seedlings two times at about 4 to 6 weeks old. You can find old articles documenting the effect of chilling on fruit production. I am not aware of anything documenting the effect of water stress. I have had outstanding results for the last 20 years using these simple genetic triggers to make my tomatoes more productive. There is something to be said when one of my customers goes to a seed store and buys 24 plants of the exact same variety I sell and grows my plants side by side with the typical hot-house plants. I personally watched him pick 9 buckets of tomatoes off of 24 of my plants where he picked 2 buckets from the hot-house plants.
Other than this, there are some amazing things you can do when grafting one color tomato on top of a rootstock for another color. I’ve seen white tomatoes turn red as a result of such a graft. Not only that, the seed grown from the “white” tomatoes (that were turned red by graft translocation) wound up producing red fruit then reverted to white in the next generation. Graft translocation makes me shake my head sometimes.
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Ivan Michurin believed that seedlings could be influenced by grafting them onto a productive rootstock. He called it mentor grafting. The caveat seems to be that the tree being mentored must be a young seedling.
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Chill how much? Spring is typically cool here and the plants grow slowly but when it warms up some produce well and others don’t.
rootstock effects on scions are some of the most intriguing, amazing, and mysterious biological phenomena
even something as mundane as genetically-unmodified rootstock recently grown from seeds-- if a really old cultivar budwood clone is serially grafted to such seedlings, will help induce the old clone revert to some degree of meristem plasticity.
If you want an old clone on its own roots, you may have to graft it serially to several youngsters before attempting to airlayer.
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tomatoes need at least 8 hours between 35 and 40 degrees F followed by daytime temps in the greenhouse of at least 90F. The combination of low temps at night followed by high temps the next day trigger changes in tomato seedlings that result in higher fruit production. Water stressing seedlings has to be done twice to be effective. Between 4 and 6 week old seedlings are deliberately left without water until the leaves start to wilt, then water heavily. After the second time without water, the seedlings will grow much more massive root systems. The plant continues to grow a larger root system after it is transplanted to a permanent location.
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With red fruit being dominant it makes sense to see some segregation in future generations.
Graft hybridisation breeding is relatively unstudied and not well understood, the few peer reviewed papers that have been published on the topic are fascinating. One example is:
Taller J, Yagishita N and Hirata Y (1999). Graft-induced variants as a source of novel characteristics in the breeding of pepper (Capsicum annuum L.). Euphytica 108: 73-78.
I have been grafting tomatoes with different leaf types (recessive leaf scion onto dominant leaf rootstock), bagging the flowers, planting hundreds of seeds from each replicate, and documenting any changes in leaf type of the seedlings. I am only seeing up to 4% of the seedlings displaying differences in leaf type, sometimes less than 1%, depending on the conditions, so have to plant many hundreds of seeds. There is so much to learn on this topic.
Some plants that cannot be cross pollinated but can be grafted to one another may be able to transfer some genetic material. A future project is to graft tomato scion onto hot pepper rootstock and see if any of the seedlings grow a hot tomato.
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Here is another article on the same subject.
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Thank you guys for responding and providing additional research and personal experiences. I’m running out of daylight and will soon lose fair weather for several months. This is an intersting topic to me, and you’ve given me points to ponder over the winter months. 
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Great to meet plant nerds right? This forum is the horticulture equivalent of CES and Sturgis for electronics and motorbikes respectively 
apt analogy.
Here is the whole research article in Nature. Very technical.
https://www.nature.com/articles/s41467-020-16036-8#Abs1
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