breeding 2 seasons per year

[BenGreen]

A few questions for the more experienced breeders: if you want to increase the speed of your breeding programme, can you do a cultivation in summer outside and winter in heated greenhouse? and thus capture 2 seasons in a year?

The thing I am most interested in is whether selection in the greenhouse will have undesired side effects: such as unintentionally selecting for different temperature tolerance. I know from the Netherlands that they do winter cultivation with lights and heat and it never reaches the quality of the summer crop,
but does it influence selection significantly?

I am located at latitude 39,9248, which might have an influence on winter sun hours.

Does anyone here do winter cultivations in a greenhouse for their breeding?

[MissS]

AKMark is in Alaska and breeds his own tomatoes. He grows most of his tomatoes in a greenhouse and also has some outdoors. Why not check with him if he does not find this thread on his own.

[PaddyMc]

How big a greenhouse do you have? How many seg's are you thinking of growing?

[AKmark]

I can easily do two generations per year, and three if I send seed to someone who can grow in the winter. We do look for traits such as cold tolerance, production, and early fruit set. The beauty of a GH is we can tailor the environment, I have never got accidental cross pollination either.

I am so done by October I would never do any winter crops, too cold to heat our GH's up here, other places further south I would do it.
Piece of cake.

[frogsleap farm]

if you have access to a greenhouse, two generations/yr is easy, three is possible. If you are advancing generations on early filial generations (i.e. F2-F4), you will need to be careful to advance multiple progeny per generation to manage "genetic drift", unless you are prepared to accept that risk, such as with a single seed decent strategy. When I employ a 2/3 generation/yr strategy to fine tune F5-F7 lines, I normally go with just a couple of progeny per line, and confirm uniformity. There is still some risk, but I believe it is properly balanced with the goal of "fixing"/stabilizing the inbred genotype.

[Darren Abbey]

Originally Posted by BenGreen

The thing I am most interested in is whether selection in the greenhouse will have undesired side effects: such as unintentionally selecting for different temperature tolerance.

Alternating selection forces can have the impact of selecting for plants that can handle a broader range of environments, or get your population stuck into something you don't want. The key is having sufficient plants at each stage to avoid too much drift. You can always keep seeds from previous generations to step back to if something goes awry.

Originally Posted by BenGreen

Does anyone here do winter cultivations in a greenhouse for their breeding?

I don't have a greenhouse, but I have grow-lights setup in my basement. I've done several chile crosses this winter, as well as ensured the selfing of the best from the previous generation of a project.

Next year I'll probably be selecting and growing micro-sized tomato plants in my basement too.

[BenGreen]

How big a greenhouse do you have? How many seg's are you thinking of growing?

We have a 200m2 greenhouse, but we actually use it as our nursery so it does not have too much cultivation area. I am already using it to do 2/3 generation of pot tomatoes, but those are on the tables with a more uniform temperature. So the question was mostly about soil temperature.

Thanks to all others for the very informative replies, we are simply going to give it a try

[PhilaGardener]

Let us know how it goes for you! Good luck!

[katwest]

Hi, can you explain the concept of genetic drift a bit more? Not sure I'm following the risk...

[frogsleap farm]

Originally Posted by katwest

Hi, can you explain the concept of genetic drift a bit more? Not sure I'm following the risk...

Genetic drift is the inadvertent loss of genetic variation due to small sample size. For example in a F2 generation derived from a F1 of dis-similar parents - there will be abundant genetic variation among F2 family members, each carrying a different combination of traits from the F1 parents. If you can only grow out 2-3 F2 individuals, you have a very small sample of the potential gene/trait combinations available - and have a high risk of not capturing the ideal combination you are looking for.

[katwest]

Interesting - thanks for the explanation!

[crmauch]

Originally Posted by frogsleap farm

Genetic drift is the inadvertent loss of genetic variation due to small sample size. For example in a F2 generation derived from a F1 of dis-similar parents - there will be abundant genetic variation among F2 family members, each carrying a different combination of traits from the F1 parents. If you can only grow out 2-3 F2 individuals, you have a very small sample of the potential gene/trait combinations available - and have a high risk of not capturing the ideal combination you are looking for.

How many of the F2 generation would you usually plant? And of the resulting plants how many would you select to go forward? I'm thinking your numbers would get very large, fast. If in the F2 you grew 10 plants and 3 of those had traits you were looking for and grew out 10 of each of those for the F3 (you'd now be at 30 plants). If in the F4 you're still looking to avoid unwanted drift you could be looking at 90 plants. Are these the kind of numbers you would be talking about?

[Darren Abbey]

Originally Posted by crmauch

How many of the F2 generation would you usually plant? And of the resulting plants how many would you select to go forward? I'm thinking your numbers would get very large, fast. If in the F2 you grew 10 plants and 3 of those had traits you were looking for and grew out 10 of each of those for the F3 (you'd now be at 30 plants). If in the F4 you're still looking to avoid unwanted drift you could be looking at 90 plants. Are these the kind of numbers you would be talking about?

Every "stable" variety of tomatoes is inbred to the point where there is essentially no meaningful heterozygosity left. With each successive generation there will be less genetic diversity to sample from. The upshot of this is that it would be most important to grow larger numbers in the early generations (F2, less so F3). Once you get a few generations down the line, the plants will be homozygous for most genetic loci and so each plant will be very similar to any other. Essentially we're managing and using drift to our ends, instead of avoiding it.

You only have to save seeds from one plant each generation, if you choose wisely which plant to save seeds from. I was growing out of one batch of seeds (F3s?) for one of my projects for several years (at about 4 plants a year) until I found a plant with better fruit last year. I'll probably be growing out of the seeds I saved from that plant for the next several years as well. I still have those older generations of seeds in storage if I later decide this lineage isn't turning out how I thought it might.

[KarenO]

Originally Posted by Darren Abbey

Every "stable" variety of tomatoes is inbred to the point where there is essentially no meaningful heterozygosity left. With each successive generation there will be less genetic diversity to sample from. The upshot of this is that it would be most important to grow larger numbers in the early generations (F2, less so F3). Once you get a few generations down the line, the plants will be homozygous for most genetic loci and so each plant will be very similar to any other. Essentially we're managing and using drift to our ends, instead of avoiding it.

You only have to save seeds from one plant each generation, if you choose wisely which plant to save seeds from. I was growing out of one batch of seeds (F3s?) for one of my projects for several years (at about 4 plants a year) until I found a plant with better fruit last year. I'll probably be growing out of the seeds I saved from that plant for the next several years as well. I still have those older generations of seeds in storage if I later decide this lineage isn't turning out how I thought it might.

Darren, If you found a new and quite different segregation in an F4 growout, would you consider it to be like an F2 as far as stability? ie requiring another 5 or so gen to stabilize the new seg?
KarenO

[Darren Abbey]

Originally Posted by KarenO

Darren, If you found a new and quite different segregation in an F4 growout, would you consider it to be like an F2 as far as stability? ie requiring another 5 or so gen to stabilize the new seg?
KarenO

That would come down to experiment. It could be you've finally recovered an interesting set of double-recessives that were hiding in previous generations... or you've got an unexpected new cross in the mix. In the first case, I'd expect it to be pretty far along the line towards being stable already and the next generation should be much like it. (It is definitely possible to get strange things appearing in later generations, it is just increasingly unlikely with increasing generations.) In the second case, the next generation would again appear to have all sorts of things going. They would essentially be F2s and the interesting plant would have been a new ~F1.