Seedless pepper genetics

PollenNut

PollenNut

I'm getting 100% seedless peppers on this C. annuum 'Variegata' x C. baccatum 'Sugar Rush Peach' and I'm wondering... perhaps the pollen might be useful to breed seedless peppers?
 
At any rate, the seedless peppers in this one f1 seedling is a good reason for growing out more than 1 f1 seedling when you can as there is variation even in the f1 peppers and even more so when your dealing with interspecific hybrids versus intraspecific hybrids.
 
https://youtu.be/5HqRY9yXJ7c 
 
 
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How come there is variation in the F1? It should be homogeneous, no? However, if there is homogeneity, that's a good find. If not, it might be a good idea to clone to propagate.
 
Dulac said:
How come there is variation in the F1? It should be homogeneous, no? However, if there is homogeneity, that's a good find. If not, it might be a good idea to clone to propagate.
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I think there is heterogeneity in the F1 stage whenever the two parents were not homogeneous themselves.
 
I was thinking chromosome crossing over could cause variation in the F1, too, but I realized it wouldn't if both parents were homozygous. However, it would make any cross with at least one heterozygous parent even more varied. I need to pick up a good book on genetics, its been a little while since I've thought through the basics, and I never took a genetics class in college despite getting a microbio minor.
 
Most chromosome crossover of note occurs in the f2 for the most part as it is often assumed that the parents used in the cross are homozygous.
 
However, I've seen mention of many new genes being discovered or mutating when one makes an interspecific hybrid. This being an interspecific hybrid it makes sense that one of the seedlings might have a mutated gene or phenotype. Please note though, mutations can happen at any time and in any generation regardless of whether the cross is an interspecific (different species x different species) or an intraspecific hybrid (same species x same species). 
 
The incidence of mutations can be increased by chemical means as well. Caffeine has been used to induce mutations for instance in seed. 
 
I've grown out thousands of cacti seeds for instance... 1 in 1000 might be variegated, crested, monstrose, etc. despite those mutations not being present in any of the parents. This incidence of mutation increases of course if one of the parents does have a mutation.
 
In Brugmansia for example, you can cross a pure species versicolor with a pure species aurea and get a very rare double or triple flower phenotype if you grow up several thousand. Or... you could simply start with a double flower and work with that.
 
There is often an increased magic of mutation or new phenotypes often seen with many plants when interspecific hybrids are made.
 
Not all traits are inherited in a dominant/recessive mendelian way as well. Some traits are quantitative in nature which is another reason for growing out large numbers of seeds with a cross. 
 
Traits that are quantitive in nature with Capsicum include fruit wall thickness, productivity, etc.  
 
Hmmm, that's interesting they can cause mutations. I think I forgot about that. Is it possible to safely use methods of mutations such as caffeine at home? I'm assuming it's some sort of concentrated caffeine.
 
Dulac said:
Hmmm, that's interesting they can cause mutations. I think I forgot about that. Is it possible to safely use methods of mutations such as caffeine at home? I'm assuming it's some sort of concentrated caffeine.
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Yeah, mutagens are the class of chemicals that can induce mutations. I've never heard that caffeine could induce mutagenesis, but in general if a chemical is a mutagen its going to be really dangerous (because they target DNA). Or not that mutagenic (which is probably the case for caffeine). More of use to the person w/o proper safety equipment or lab experience would be the non-chemical mutation methods, including microwaves.
 
I've thought it would be cool to try to induce mutagenesis in seeds and see what I could get out. And actually people in industry do this - there's at least one famous pepper that came from this. But it requires growing out a lot of seeds, which would be difficult to do. Plus, again, most chemicals used for this are nasty. And figuring out the right amount to use is tough, b/c if you use too little, nothing happens, and if you use too much, the seeds become non-viable.
 
https://link.springer.com/chapter/10.1007/978-3-642-69823-1_15
 
(Amacher et al. 1980). Caffeine, alone or in combination with other agents, has been reported to have cytotoxic, DNA replicative, genetic, carcinogenic, and teratogenic effects…. It produces chromosomal aberrations in both plant and animal cells, although high concentrations are needed (around 10- 2 M) to provoke these effects
Caffeine also can potentiate the genetic effects of other agents, including radiation and chemicals. At least some of these effects can be attributed to its action in modifying DNA repair processes: effects on photoreactivation, excision repair, and post replication repair have been reported in various organisms.
 
PollenNut said:
https://link.springer.com/chapter/10.1007/978-3-642-69823-1_15
 
(Amacher et al. 1980). Caffeine, alone or in combination with other agents, has been reported to have cytotoxic, DNA replicative, genetic, carcinogenic, and teratogenic effects…. It produces chromosomal aberrations in both plant and animal cells, although high concentrations are needed (around 10- 2 M) to provoke these effects
Caffeine also can potentiate the genetic effects of other agents, including radiation and chemicals. At least some of these effects can be attributed to its action in modifying DNA repair processes: effects on photoreactivation, excision repair, and post replication repair have been reported in various organisms.
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That's an interesting reference - I don't have access to the book through my university for some reason, but it does look like the effects (at least from what you've listed and the papers they cite) are in active cells mostly. Caffeine isn't a very reactive molecule - it degrades easily, but it's not going to go around methylating your DNA bases like some other mutagens would. It probably (in accordance with its structure and its attribution to affecting the repair process) interferes with cell DNA replication mechanisms, since its shaped not unlike a purine or pyrimidine base. If this is the case, it'd be of little use in mutagenesis of seeds, since there's little to none of these mechanisms working while the seed is just sitting around. But really an experiment is all that's needed here - and sorry for hijacking your thread.
 
Pimental
 
Pimental said:
That's an interesting reference - I don't have access to the book through my university for some reason, but it does look like the effects (at least from what you've listed and the papers they cite) are in active cells mostly. Caffeine isn't a very reactive molecule - it degrades easily, but it's not going to go around methylating your DNA bases like some other mutagens would. It probably (in accordance with its structure and its attribution to affecting the repair process) interferes with cell DNA replication mechanisms, since its shaped not unlike a purine or pyrimidine base. If this is the case, it'd be of little use in mutagenesis of seeds, since there's little to none of these mechanisms working while the seed is just sitting around. But really an experiment is all that's needed here - and sorry for hijacking your thread.
 
Pimental
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There is absolutely no reason to let the seed just sit around while treating it with caffeine. You could for instance, germinate the seed in the caffeine. 
Many mutagens might indeed need for cells to be replicating for an effect to be noticed.
 
PollenNut said:
There is absolutely no reason to let the seed just sit around while treating it with caffeine. You could for instance, germinate the seed in the caffeine. 
Many mutagens might indeed need for cells to be replicating for an effect to be noticed.
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That's true, you could. I just looked up - and was surprised to find out that - seeds already have plenty of cells in them prior to germination (I guess I'm too used to thinking about bacteria...). This makes sense, but I didn't realize it before. Regardless, it means that you'll end up with a highly variegated plant. Different mutations will occur in different cells, and you'll end up with a plant with cells of a variety of genomes. Now it makes sense to me why the Enjoya pepper can only be propagated vegetatively and not by seed...
 
Obviously you'll get some mutations into the offspring. But only the mutations in whatever cell eventually ended up producing the seeds. The best way to get as many mutations as possible into the cell would probably be to hit it while there were as few cells as possible. For peppers, the common procedure is outlined in "Ethyl Methanesulfonate-Induced Seed Mutagenesis of Capsicum annuum" by Alcantara et al.
 
https://en.wikipedia.org/wiki/Mutagen contains a good list of mutagens, and some wouldn't be all that hard to use. The first two categories don't require growth.
 
Surflan can also be used to induce a tetraploid plant along with other chemicals if one really wants to chase down new phenotypes... sometimes the best way to do that is through doubling the chromosomes. For quantitative traits like those responsible for heat, fruit wall thickness, productivity, etc. it also brings in more variables to play with.
 
For other traits like variegation, unless one starts out with a variegated conversion one may find it harder to breed for variegation. 
 
Seeds that have just germinated can be treated in that manner to produce your desired tetraploids. 
 
Also of note, fertility can often be restored to interspecific hybrids that have their chromosomes doubled. It may even be worthwhile to make the initial cross with tetraploid plants to begin with.
 
40.4 mg per 0.1ml of solution of  Suflan via Southern Ag-12401 A.S. Pre Emergent Herbicide. Draw up 0.1 ml surflan ad mix with 0.1ml DMS0. Remove 0.2 ml water from 1 liter and then add half your surflan DMS0 solution back into the 1 liter solution. Add .1 mL DMSO. This should give you 20.2 mg oryzalin per liter and give you your converted seeds after a 6 hour soak.... should work
 
That's pretty cool - ploidity is definitely something I want to look more into, as I can't say I quite get it. But its pretty cool.
 
Thanks for the info!
 
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