Male Sterility

[hillbillypie]

Last year I used Plum Regal as a female parent in a cross with an OP variety. It is my understanding that one of the parents in Plum Regal has the male sterile gene.

In addition to that, I have a selfing line that has the ms-2 gene that I want to breed with a few other OP lines. I suppose I will have to use this one as a female in the same way that I used Plum Regal.

So, my question is twofold. One, what problems/issues do I need to be on the lookout for with my F2 seedlings from the Plum Regal?

Secondly, how in the world is it even possible to have a male sterile selfing line? In my mind, I can't wrap my brain around something being selfing and yet sterile. Can anyone explain?

--Steve

[tomato]

It depends on the form of male sterility. Several of the wild species of tomato have a gene that conveys self sterility, but produce normal pollen, they just can't fertilize their own flowers. In this case, you could have two self sterile varieties but they would be cross compatible.

Male Sterile is a different problem. Most male sterile plants do not produce normal pollen and therefore cannot self fertilize. I haven't read up on the details because I will not knowingly grow a male sterile tomato. You can find lots of references by searching for "male sterile tomato".

I should note that Besser cherry, which I have in my seed inventory, carries a hidden gene for male sterility that I have to rogue out regularly.

DarJones

[frogsleapfarm]

Male sterility in tomatoes has been of some interest as a means of simplifying hybrid seed production. There have been multiple male sterile (ms) genes described, each, to a varying degree of stability and reliability, disrupting pollen development and viability. Male sterility is a common mechanism in crop plants for managing pollination (cross vs self) in seed production. The ms plants are usually fully female fertile, so are used as the female parent in hybrids. I believe all the ms genes in tomato are recessive, so are only expressed in the homozygous state - not in hybrids, like Plum Regal. One of the most commonly used ms genes in tomatoes is linked to anthocyanin-less hypocotyls, so the recessive ms plants can be identified as seedlings.

[hillbillypie]

I understand that it is recessive. It is because of that I am confused. How is it possible that I have an accession that is ms-2,ms-2 and not MS-2, ms-2?

If it is male sterile how is it possible to have a pure breeding line of male sterile?

Also, I should see some male sterile segregants in the F2 of my cross. Will it be the typical 75-25? I seem to recall culling some plants of a variety last year because they had clear green stems and I was told this was a marker for male sterility. Any merit to that?

[frogsleapfarm]

Jan 31, 2012 10:59:12 GMT -5 hillbillypie said:

I understand that it is recessive. It is because of that I am confused. How is it possible that I have an accession that is ms-2,ms-2 and not MS-2, ms-2?

If it is male sterile how is it possible to have a pure breeding line of male sterile?

Also, I should see some male sterile segregants in the F2 of my cross. Will it be the typical 75-25? I seem to recall culling some plants of a variety last year because they had clear green stems and I was told this was a marker for male sterility. Any merit to that?

From a ms/ms x +/+ cross, in each filial generation you would have ms/ms and ms/+ plants (the +/+ segregates would decrease in frequency with recurrent selection for the ms phenotype) - in theory you eventually develop isogenic lines, identical except at the ms locus where one line is ms/ms and it's isogenic line is ms/+. The ms/+ becomes a "maintainer line" to cross with ms/ms to regenerate the ms phenotype. This is a lot of work, and part of the reason male sterility is not widely used in hybrid tomato seed production.

The gene controlling clear green hypocotyls (anthocyanin-less), is linked to one of the ms alleles (ms-10?). In ms/ms x ms/+ progeny you use the anthocyan-less hypocotyl phenotype to select ms seedlings.

[hillbillypie]

Thanks! I was not aware of maintainer lines. That makes sense now.