Frost and Cold Tolerant Tomato Breeding including epigenetic and regular genetic

[Joseph Lofthouse]

Ah.... The confounding effects. Always present in plant breeding. Did that plant thrive because it is resistant to blight? Or because it didn't get infected? Is that rye plant 25% taller than the rest because of genetics? Or did a vole die under it's roots, thus providing an extra boost of nitrogen?

Do short stubby tomato seedlings survive frost because they are protected by taller plants? Or because they are closer to the warmth of the ground? Or both?

My general belief is that I can't understand, nor control for, the confounding effects, so I focus on bulk-selection over decades, as my go-to plant breeding strategy.

 

[Steph S]

LOL vole.   
Worth mentioning as an aside, that my tall BT emmer from last year is tall, while the short emmer is short, so that at least was a genetic thing.
OTOH I really don't know why I have patchy survivorship among the grains - did frost get through my row cover tatters?  Was rain penetration uneven?  Did wireworms eat the roots?  Oh well...  We're going with the survivors, whether they're "the lucky" or had some genetic edge.

I stopped starting tomatoes too early for a couple of years.  I was tired of seeing first clusters not set for the effort, but then starting late means they get the scorching in July and it's too late to be setting when it gets hot.  I need my tomatoes to set up when it's cool and ripen up when it's too hot to be setting.
So this year it was early again.
Those seedlings got all the epigenetic prompts they need for the season, that's for sure.
It's a crapshoot starting early, because the weather's so unpredictable.  But even so, I think I'm ahead of the game with fruit set and growing before the end of June.  If we hit some heat bumps I could, technically, let them keep on going longer and set up again when it cools off.   I probably won't do that because I prefer to limit the time I spend growing our tomatoes.  If we hit some cold bumps - I'm not a bit worried about that.   These plants spent what, nearly a month with close to freezing temperatures at night and quite a few days not over 60 F or an hour or two at best above 60, while sitting in beer cups. 
The plants I put outside weeks earlier than I would normally dare, are shrugging off the 'nearly frosty' nights.  It's true we have not had a white one here in spite of the threats this year.  Could still happen but...   no I'm not worried.  Minimal protection is enough, because all their epigenetic resistance has been activated well and truly.

I am deeply curious about the work you guys have done, and once I actually finish a couple projects I want to open up some space to try out the OPs you like and the lines you've created.  I would treat them the way I treat mine, which is as much as I can do to bring out the stress tolerance genetics.   Would also be happy to throw you some seeds of mine  to see how the tomatoes that we've trained to the environment here also perform in your trials.

I do think there's a big difference between wet cold and dry cold, also the difference between a cold night with a hot day, and the long bouts of sunless cold days and nights that we get here.  It's no surprise to me that people in different places have different favorites, because they suit that environment and are at their best.
Heat stress is as big a factor as cold stress, if not more, when it comes to tomatoes.   And the response to variable extremes.  Every year I see my plants wilt and freak out when it suddenly becomes hot and sunny with high UV after a long stretch of grey and cold.   Give them a week of sunny weather and they've adapted to that.  But there's no question in my mind, it's not easy for a plant to be ready for both.

I know there are genetics in some plants at least, that respond to all kinds of stress.  The chemistry for stress tolerance just isn't there in tomatoes in the same way.

[William S.]

I wonder though, talking improved protocol, say instead of throwing a whole flat out in the cold, maybe smaller flats or just the outer part of one of those flats with holes so there are less microsites and the physics is more similar for the individual seedlings.

This spring when I was done with my interspecies hybrid search on some flats I tossed them out into the cold and it was definitely the understory in the center of the flat that survived the longest. I think that was just physics.

Another improvement might be to follow a suggestion from Darrel Jones if I recall it correctly. He stressed a genetic difference between cold and frost tolerance as two different goals and suggested refrigeration for cold. He said non cold tolerant seedlings will turn to mush. Cold tolerant will be fine. So maybe just a little community pot in the fridge for a week for say a segregating population? Also maybe some test pots of seedlings of parent or potential parent varieties.

I suspect that Black Strawberry, Lizzano F1, and a number of currant tomatoes are cold tolerant given this weekend's fruit set findings. Kind of surprised there aren't a few more. Might be that they had some transplanting advantage and some cold tolerance. Fridge test would be interesting on them.