Selecting F2 Seeds

[Solanum315]

So I am working on a growout for an accidental cross between Black From Tula and what I am fairly certain is a commercially grown saladette tomato that I have mostly stabilized. Now that I am growing the F2 generation, I am starting to see wide variances as expected. Some fruits are small saladettes with varying colors, some with BER and there is one plant that is throwing beefsteaks.

My first impulse is to save seed from the beefsteak once I confirm it has a good flavor as I prefer beefsteaks.

My question is whether or not the fruits with BER would be more likely to produce offspring with BER and what the likelihood is that an F2 saladette would turn around and have beefsteak offspring? On one hand it seems that since F2 is the beginning of gene segregation, that most likely the different lines would continue in the same direction. On the other hand, I could see it still being a crapshoot as to whether F2 tomatoes would stay true to form until F6....

The BER might just be differences in the soil where they're growing. I've got about 17 plants of the same kind of true-to-type paste tomato, and a few of them (in the same tomato patch) are getting BER, while the others don't seem to be affected. I'm guessing soil differences are responsible. It's really hard to say whether seeds from fruits with BER would be more likely to produce the same. They might even be less likely (depending on what is true about the science of acclimatization). However, if it's a genetic thing (with both having the same soil), then yeah, they'd probably be more likely to get BER.

Seeds from BER fruits are less likely to be mature/viable, however (since BER fruits ripen faster than is natural). The seeds that mature first in the fruits are more likely to be the viable ones you'll get. I often wonder if the seeds that mature first will produce plants that mature faster.

By beefsteak, are you talking about the fruit shape, the fruit size or both? I don't have a definitive answer for you, but the answer to the question I asked might help someone who does.

[bower]

Although BER is a physiological condition, it's also true that certain varieties are more prone to it than others. Shape genetics does seem to play a role in how likely is BER, but it sounds like you could just be having a bad year. OTOH, selecting away from it is not a bad idea.


As regards beefsteak, there are two QTL's (of about ten) that govern locule number and have a major impact on the size of fruit. lc (locule number) gives 3-4 locules and could be present in your saladette as well. fas (fasciated) gives >6 locules and would be in the BfT parent only. So it seems that would show up in your F2 as a recessive that is 1/4 at best. So if I were you I would certainly save seed from any beef shapes you get in the F2, as it represents your chance to recover size.
Frogsleap published some interesting data about size recovery in crosses between large and small fruit, where they found the results were strongly skewed towards smaller fruit. Search in the Crosstalk forum and you'll find links and discussion of that issue.


Here is some reading about locule number: Figure 6 is a nice one showing the progression from wild type (2 locules) to beefs.
http://www.plantphysiol.org/content/156/4/2244

[Solanum315]

Thanks for the replies. Very interesting paper although some is a bit over my head. I will definitely focus my efforts on the beefsteak line.