Frost and Cold Tolerant Tomato Breeding including epigenetic and regular genetic

[Steph S]

Glad to hear you got some survivors. 
Even though it's hard to disentangle random chance, micro-environment and other non-genetic factors, the individuals that survived may carry forward the 'event memory' as a tweak on gene expression.  Or who knows, it may even affect the 'shuffle' when segregating. 

The state of the roots seems to be a big factor in cold event survival.   Wet roots do worst, in my experience.  The sandiness that you mentioned, might be a factor if those roots were better drained. 
Also I've noticed that end of season adults with full root systems will sprout again after the tops have been killed by hard frost.  So it's interesting that you noticed smaller plants having better survival.  I wonder if those phenos put more energy into growing the root system before investing in the tops.
I have encountered a few vars that are like that - Zolotoe Serdtse is one.  You can't force them to bud in a small pot, and they don't put on top growth as soon as you plant out.  They want that volume of roots before they will invest. 
I wonder if root vs shoot investment is part of the strategy employed by wild tomato relatives.
I suppose it could be investigated by growing in clear containers.

[AndrewB]

Deeper sand seems to enhance survival. Probably holds and radiates heat.

Small plants seem more likely to survive.

I would think it has more to do with sand draining faster and thus less water. When cold hits its usually the water that kills.

Younger plants do seem to do better of any crop.

Dar Jones still has some very cold and frost tolerant tomatoes.

https://growingfruit.org/t/talking-about-tomatoes/26543/42

Yes, but have to clarify that tomatoes are NOT frost tolerant meaning that they are susceptible to frost forming on the leaves and that is true for all wild species. It is possible to select for cold tolerance which really breaks down to a group of genes that code for improved transport in the stem of the plant at low temperatures. These genes mostly come from S. Habrochaites which is arguably the most cold tolerant of the wild species. LA3969 has most of the required genes. Cultivar Earlinorth has the ft gene which permits flowers to set fruit down to 40 degrees F. Of the varieties you can easily find that exhibit excellent cold tolerance, several are from Russia such as O-33. Siberian is one of the easiest to find. Tastiheart is a variety that I accidentally selected for cold tolerance back in 2007. Tastiheart can handle temps down to 22 degrees F if you drop a cloth over the plant to prevent frost forming on the leaves. LA2175 is the best of the pure S. Habrochaites lines I grew for cold tolerance and has excellent foliage disease resistance.

[William Schlegel]

In 2017's frost event I planted out very large plants and many resprouted. Last year end of the season plants were resprouting. Tried to cut and reroot some resprouts.

I expect additional survivors from resprouting both stem and base but do not expect smallest plants to resprout. Some completely lysed down to the ground and collapsed. Others still have significant stems that look ok. This list is of plants on the cold field that look ok with leaves intact.

The 30F met the dew point otherwise not. That means some plants may have stayed dry. Apparently a wet frost is harder to survive from things Dar Jones has said. All the fields were unwatered yet this year so dry as it's been a dry spring.

The plants I did cover lost the tip on some where the cover touched.

Small plants comment also mainly pertained to the coldest field.

I have seed for 0-33 and Tastiheart. Did not grow it this year as did not intend to explore frost this year particularly. In 17 I
think 0-33 succombed as did the Russian strains.

2017 also was remarkable in that tomato seed germinated by May 5th meaning ten day old seedlings survived frost on May 15th. Every other year including this one, no germination has occurred until after last frost.

[William Schlegel]

I wandered around the gardens today flagging surviving tomatoes. Quite a few survivors really, I counted 23 in the hard hit slushy garden.

One that caught my attention was one F4 Sungold survived
with nothing obviously different from the rest of the clump. Though I've seen similar things with non-segregating varieties. Why does one tomato collapse to mush and the next look untouched on occasion ?

Then when I got home the weather forcast changed to 36 F that could easily drop down to freezing. I planted more today including the irreplaceable LA2329 growout thinking it was finally safe. Will take my chances I guess.

[William Schlegel]

Found a lot more resprouts yesterday. Interesting. Wonder if it does cause epigenetic change to freeze to the ground and come back? This is basically the second time in five years.

[Steph S]

I'd be pretty sure it causes epigenetic changes, at minimum.
The second question is, do these events affect the chances of transposing elements etc when the time comes to set seed.  It stands to reason, if you need to adapt to extremes then shuffling the genes in less usual ways would be an adaptive response.  Especially for an inbreeding species.

[William Schlegel]

My Mission mountain sunrise bicolor tomatoes are descended from a 2017 frost survivor Blue Gold and a unknown potato leaf from Joseph's old mostly red landrace. They seem to have a lower response about 1/2 than Exserted orange. Exserted orange was supposed to be hab x big hill but came out just orange and seemed fully domestic, though a common source of orange is sun gold F1 and it has one F4 or so that survived this frost. By response I mean either surviving with top growth intact, stem intact, or resprouting from the base.

The variety Bosque Bronze seems to not be resprouting so far. Looks like stem was largely intact- no collapse, but no new growth yet. May just be too soon.

Some plants were just to small to come back.

Some got lucky microenvironments and survived.

The resprouts though are just good resprouters but that is a lot of stress.

Wondering if I could / should make 2022 about cold /frost tolerance.

One thought is to do a big habrochaites grow out and deliberately plant them to soon maybe in a couple waves starting at the end of April. To ensure a frost trial.

Joseph had that methodology where he would half freeze a seedling tray with a tomatillo control and keep the survivors.

[Steph S]

Aha that is a clever method, takes away the microenvironment variables so what you get is selection for frost tolerance.

OTOH your field trial is totally relevant to the specific conditions, including the soil, microenvironments, frost, heat, etc.

[William Schlegel]

Refrigerator, freezer, and growth chamber space would be really cool. Hmm I know of a refrigerator that is often empty that time of year where I might be able to stick a tray.

The seedling method is good because you can have a very dense population in a small space.

In the field it's really kind of a mess. I have the urge to rototill it (wont) because of the perennial weeds Cirsium arvense and Cardaria or Lepidium draba

[William Schlegel]

62 survivors in my slushy field.

[William Schlegel]

I think in my slushy field I lost just Terrior strain galapagos tomato, 42 days, Bosque bronze, chariot f3, wild child, and weight in gold. That I found today anyway. Replanted a few things today. Had some leftover regular leaf bicolors from the Mission Mountain sunrise project since I decided to make that Potato leaf.

[William Schlegel]

https://phys.org/news/2021-06-crispr-highly-efficient-gene.amp

They used tomatoes amongst the experimental crops.

Highly interesting because it seems we can now just manipulate epigenetics directly.

[Steph S]

I do like his attitude about bringing out the positive potential that's already present in the plants.

OTOH, the existence of adaptibility or "free will" in plants, which allows them to choose a strategy for survival depending on circumstances, seems somehow more important to me than the opportunity to manipulate their genes and switch something on permanently which could be disadvantageous in an extreme environment.

Just for example, I noticed this year of alternating extremes of heat and cold (as I have in some times past) that virtually all of my tomatoes chose to fatten up a first fruit to near maturity, before growing up any of their other first cluster sets.   This is not ideal for me as an animal that hopes to eat a full truss of fruit.  I would rather see every set growing up progressively as new ones are made, even if it means that they are all smaller for the usual growth period, instead of one large fruit hanging there precocious to the others.    I was relieved to see at a certain point that the deferred fruit started to grow and fill up the truss.  But those first fruits which were fattened at the others' expense will be ripe long before them.

I don't know exactly what triggers are involved, that produced this reaction in the plants, and if it had been up to me to decide, I would've had them working on the full truss at once.   This is the kind of thing that could probably be switched on permanently, and prevent the plants from choosing to do otherwise in any circumstance.

So think about the advantage that they got, in devoting their early energy to a single fruit.  In a disastrous year of extremes, this strategy ensures the best chance to mature seeds.  Suppose the extremes of heat and cold continued or got worse, the first fruit might be all that they had a chance to ripen.   It would not feed me, the animal, for that year, but it would produce viable seeds for the next. 
And if my disappointment at getting a single fruit would be bad, think about getting none at all, and no seeds, because the fruit were all too small and immature when the worst case scenario came along.

The ability to switch on some epigenetic features permanently is, in a sense, no different from switching something off, if indeed you remove the possibility for the plant to choose which state it should be in, depending on circumstances.

[Roland]

I wandered around the gardens today flagging surviving tomatoes. Quite a few survivors really, I counted 23 in the hard hit slushy garden.

One that caught my attention was one F4 Sungold survived
with nothing obviously different from the rest of the clump. Though I've seen similar things with non-segregating varieties. Why does one tomato collapse to mush and the next look untouched on occasion ?

Then when I got home the weather forcast changed to 36 F that could easily drop down to freezing. I planted more today including the irreplaceable LA2329 growout thinking it was finally safe. Will take my chances I guess.

William,

Can u tell something about the serigation of the Sungold F2 plants and later generations?

[William Schlegel]

Roland, in my experience Sungold leads to orange tomatoes a lot like Sungold but a little more variable in size and flavor. Sungold and descendents can be a little bit exserted and can outcross. I would consider a red to be an outcross. It has never been a major grow out for me so inadequate data.  Though I suspect you could take Sungold F1 as decent germplasm for early and tasty tomatoes and then select for preferences you might have. There are lots of dehybridizations on the market.