US Nicotiana Germplasm Collection 2013 Nursery

[deluxestogie]

The problem is that I don't really know. I am aware of the usual guidance about diversity and breeding (for both plants and animals). The numbers involved in tobacco breeding are many orders of magnitude (powers of 10) greater than most of the breeding numbers we deal with. And since it is usually selfed, the statistics come down to a gazillion variants of a tetraploid set of chromosomes. There is immense diversity in the genes of a single tobacco plant.

I may be missing a crucial factor here.

Bob

 

[DGBAMA]

Would be very interesting to take seed from a single prime plant of a single variety and distribute it to 20+ growers with different climactic and soil conditions around the world. Then each grower document their growout conditions from planting to harvest and compare the results.

 

[deluxestogie]

I want to make it clear that I am not saying the Skychaser is wrong in his assertions about tobacco seed saving. His method of seed production is admirable and better than the usual practice of saving seed from one or only a few exemplars.

Rather, my sense of it is that the high seed count, the tetraploydy (doubled chromosome number) of tobacco, its strong tendency to self-pollinate, and the subsequent tiny fraction of selected seed for most grow-outs all conspire to render the usual seed saving rules for genetic diversity significantly less effective, when applied to tobacco, as compared to other crops.

This question troubles me, and kept me awake. In searching the literature for studies of the effects of inbreeding/cross-pollination on single variety tobacco (as opposed to the much more common studies of hybridization, heterosis {out-breeding strengthening} and trait amplification), I was not very successful.

Inbreeding depression occurs when plants have too small of a population of fellow breeders during pollination. It causes future generations of plants to be weak as demonstrated by slow growth, poor vigor and disease resistance, along with poor fruit production. Some varieties of plants such as tomatoes, which can self-pollinate, have a much smaller problem with inbreeding depression than plants such as corn, that require a population of at least 200 plants to keep from inbreeding depression.

http://scientificgardener.blogspot.com/2012/01/on-inbreeding-depression.html

Emphasis mine.

The following study, though not directly applicable, suggests that, in their case, inbreeding depression becomes significant when plants must be introduced into a new location (environment). One might regard the worldwide dispersal of tobacco seed to present such a challenge to inbred seed.

...reintroduction success was related to adaptive diversity.

http://www.ncbi.nlm.nih.gov/pubmed/16909676

The Cornell document is a general guideline for seed production, and is worth reading for all members who save seed.

Basic Concepts of Seed Production and Seed Regeneration. Cornell Univ (8 page pdf) This general guideline strongly supports Skychaser's understanding of seed saving for diversity.

I would be most interested in comments on this important subject from Jessica, as well as her colleague, Dr. R.L. (who is a plant geneticist with extensive publications on tobacco genetics).

Bob

 

[skychaser]

thanks for this. i did say that we remove all the open flowers and capsules that have begun to form (step #2, Trimming...). there are only buds and unopened flowers remaining when the bag is put on.

So then the plant in photo #4 is a different one than in photo #1 and #2 ?

 

[skychaser]

Bob, thank you for your post. I will try to hunt down some of the dozens of articles and studies I have read on this subject and post links to some of the more pertinent ones. But I just don't have time right now. I haven't even found time to read all the links you posted on the effects of light exposure yet.

..."Inbreeding depression occurs when plants have too small of a population of fellow breeders during pollination. It causes future generations of plants to be weak as demonstrated by slow growth, poor vigor and disease resistance, along with poor fruit production. Some varieties of plants such as tomatoes, which can self-pollinate, have a much smaller problem with inbreeding depression than plants such as corn, that require a population of at least 200 plants to keep from inbreeding depression."...

Corn is one of the most susceptible plants to inbreeding depression known. It is also probably the most widely studied plant there is. We grow 500 or more for seed production. Anyone can try their own experiment and quickly see the results of inbreeding depression, unless you really like corn and grow a huge patch. Save seed from your garden corn and plant it next year. You will see that your plants do not seem to grow nearly as well as the year before and the yield will fall greatly. Plant those seeds again next year and you will see severely stunted plants and drastically reduced yields of 25% or less than the original planting. In just 3 generations it will be totally worthless.

Tomatoes lie near the other end of the scale. Most do self pollinate before insects can get to them. Heirlooms tomatoes require 100 feet of separation and modern varieties even less. It all has to do with the way the flower is structured. At the very far end of the scale is lettuce. It is extremely difficult to get a cross even when planted together in the same row. The "official" recommended separation distance is 10', but nearly all lettuce self pollinates before the flowers even open. Tobacco lies in between. It is no where near corn in its vulnerability to inbreeding depression. The flower structure of nicotianas is somewhat different than tomatoes and it cross pollinates much easier at a rate of 2-10%, depending on the number of pollinators available.

Tobacco can suffer from inbreeding depression like any other plant. However, I do agree with your numbers and reasoning as to why tobacco is far less vulnerable to inbreeding depression than many other plants are. But ponder this bit of math. I take seed from 5 plants and randomly mix them together. Next season I grow 5 more plants from that same seed. The odds of me picking a seed from all 5 of the original plants for my second generation is only 20%. Statistically I am likely to only have 3 of my original 5 plants represented in generation 2. Thus the bottleneck of genes begins. Genes which may not be visibly expressed began to be lost, which may affect the plants overall viability, disease resistance, and production.

Closed pollination increases this effect even more. There have been many studies showing that open pollination will produce seed with a higher viability, better disease resistance, and production, than seed from selfed plants will. The highest quality seed will always come from large populations of open pollinated plants. I recently read a study done on the predation rate on plants from closed pollinated seed vs open pollinated seed, which until recent years was not a factor that was even considered. The study was done on a type of Horse Nettle, which is also a member of the Solanaceae family. By the 3rd generation the closed pollinated plants suffered 2.5 times the predation rate than the open pollinated plants did. I will try to find that link.

Saving seed from your own plants to grow or to share with others is one thing. I have no problem with that. But if you are producing seed for commercial sale, every possible effort should be made to produce the highest quality seed possible. Would you want to buy anything less? And if I were saving seed for a seed bank, which could very likely be the only source for that particular strain in the future, I would make every possible effort to preserve the genetics and purity of that strain.

Ok, gtg for now. I have a date with my hoe.

Sky

 

[workhorse_01]

Does the FTT seed bank do multiple seed grow outs of the same variety seed, to combine the seed after from different parts of the US.? It seems to me that would give us the highest seed viability. My plants survive what I think is a much harsher climate than what say chillardbee's would be, and on the other hand his would more cold tolerant than mine. In another post I read where sky grows certain varieties that mature faster than others. This could conceivably give me with my long growing season two solid crops.

 

[deluxestogie]

Since the quality control of seed production varies from one grower to the next, I would not be in favor of combining them into a single tub, nor of combining seed from the same grower produced in different years. Seed should be separated by grower and year produced.

As for maturation time, the GRIN data is all over the place. While I'm sure certain varieties consistently show longer or shorter maturation times, my own observations show no correlation with the GRIN data's maturations times. I suspect that maturation time is seriously affected by germination conditions, seedling environment, and seasonal weather.

Bob

 

[JessicaNicot]

Do you reuse the bags? if so, do you take any precautions so that the pollen in them this year does not pollinate a different cultivar next year?

we dont reuse the bags. they all go in the trash because they tend to get moldy. however, if you did want to reuse bags, there is no chance that pollen will remain viable from one season to the next so even if it is in there, it would most certainly be dead.

 

[Jitterbugdude]

Thanks!

 

[JessicaNicot]

Skychaser raises an interesting issue about the number of plants from which to obtain a batch of seed.

Unlike most plants from which seed is collected, a single tobacco plant may produce 1/4 million seeds, as opposed to 1 or 10 or 100 or 1000. Each seed is the combination of a random meiosis that forms the ovum, and a random meiosis that forms the pollen grain. Although a quarter million can not represent all possible combinations of all its gene pairs, it's a far bit closer to that than, say, a watermelon that produces 500 seeds.

Then, when we plant the tobacco seeds--let's say we plant 250 plants of that variety--we are randomly selecting only a tenth of 1% (0.1%) of the diversity available in our batch of 1/4 million seeds. If we combine the total seed production of 10 plants, our 250 plant selection now is a random subset of a mere hundreth of a percent (0.01%) of the diversity in our combined batch of 2.5 million seeds.

Harvesting seed from a single plant that is not an exemplar of the variety is unwise in either scenario, so planting at least a few to observe (or hundreds, if you wish) is a good idea.

Now, I will readily admit that my statistics knowledge is pretty rusty, but it seems that from a practical standpoint, the diversity represented in the 1/4 million seeds of a single tobacco plant that is exemplary of it type is more diversity than you would achieve with the 20/100 rule applied to nearly all vegetable varieties, and most other plants. And this is attributable solely to the vast number of randomized seeds produced by a single tobacco plant, when compared to other cultivated plant species.

What I'm suggesting is that tobacco is a different proposition, when compared to most seed saving. A quarter million potential offspring per individual tobacco plant per year, but utilized at a rate of 0.1%, is sufficient diversity, excluding inadequate selection of the parent plant. If your chosen parent plant is a genetic freak, then combining its seed with that of 9 non-freak plants would still leave you with a 10% chance of germinating freak seed.

I may be completely wrong about this, but I'm just not up to the statistics challenge.

Bob

you forget that nearly everything you are growing (unless you've gotten hybrid seed-- which you cannot save year to year) is inbred (at least if youre getting your seed from a reputable source). the theory is that all the seed is already more than 99% identical at every single genetic locus. yes, mutations do occur at a low rate and thus an off type plant may occur from time to time. i would hazard to guess that if your plants are non-uniform in size, but all other characters generally being the same, that you are seeing a micro-environmental effect. always remember, phenotype is genetics x environment.

 

[JessicaNicot]

So then the plant in photo #4 is a different one than in photo #1 and #2 ?

no, its the same plant i promise. the angle just might be a little different.

 

[JessicaNicot]

Corn is one of the most susceptible plants to inbreeding depression known. It is also probably the most widely studied plant there is. We grow 500 or more for seed production. Anyone can try their own experiment and quickly see the results of inbreeding depression, unless you really like corn and grow a huge patch. Save seed from your garden corn and plant it next year. You will see that your plants do not seem to grow nearly as well as the year before and the yield will fall greatly. Plant those seeds again next year and you will see severely stunted plants and drastically reduced yields of 25% or less than the original planting. In just 3 generations it will be totally worthless.
Sky

corn is a terrible example to use for seeing inbreeding depression effects when you save seed year to year because all the commercial seeds are Hybrid. hybrids are the first generation product of two inbred lines that have been crossed (in corn, this is for hybrod vigor, the fact that the hybrid will outgrow either of the parents) and by their very nature do not breed true when you save seed.

there is some confusion going around because inbreeding depression is something that occurs at the Population level. the seeds that you have, either tobacco or generally anything you buy to grow in your garden, are already at pure line status-- aka they are already completely inbred and thus cannot suffer from inbreeding depression because they are already genetically uniform.

oh boy, this is a whole can of worms... let me mull over how i can try to explain in simple terms population genetics and breeding.

 

[NRustica]

lol. Can't wait to read that.

 

[workhorse_01]

Me too, I was so engrossed, I didn't breathe while I read it. LOL

 

[jekylnz]

So would you get better offspring from growing 3 heads of 3 plants the same variety in one big bag then??

 

[deluxestogie]

So would you get better offspring from growing 3 heads of 3 plants the same variety in one big bag then??

I don't even know what that means.

The theory is that the greater the number of plants of a single variety, the greater the likelihood of selecting typical plants to bag. The greater the number of bagged plants, the greater the likelihood that you will maintain the diversity of the genes, which is a good thing.

I am certain that "pure" heirloom varietals do have variability in their population that is genetic, and not attributable to external factors (fertilizer, soil, weather, pests, etc.). But that's the point of growing multiple copies of a variety--to be able to identify outliers, and not collect seed from them.

I think adequate bagging of one typical tobacco plant is fine for most uses. Bagging 10 or 20 typical plants of a single variety is theoretically more sound, but is simply impractical for most home growers.

The only real fuss in this bagging discussion relates to production for a seed bank (preserving germplasm resources) or production for commercial distribution.

Bob

 

[DGBAMA]

If a strain is already considered pure, it would seem that "open pollenation" would be like inviting all the local "junk yard dogs" to your kennel when your best purebred female is in heat.

Unless as Jekylnz said, you could somehow confine your best plants within the same bag with a handful of bees, and hope that they cross pollinate. Not likely.

I would speculate that a quarter million seeds from a single plant should provide plenty of "diversity".

 

[DGBAMA]

Using the corn example earlier of 200 plants earlier, to keep diversity; a quick search says an ear of corn is from 600-800 kernels (seems high but ok). Presuming the larger number is true, and one viable ear per cornstalk, that would be 160,000 seeds to maintain "diversiy". A single tobacco seed head presuming 250,000 seeds would be the equivelant of planting 312 corn plants.

Bob is much more knowledgable than I, but just making a simple comparison based on numbers.

 

[workhorse_01]

I thought sky said, his open pollinated seeds were in a field by their selves? If so then open pollinated seeds would for argument sake get the best of a whole field of the same plant. If you grow inside of a greenhouse and turn clean bees loose inside it, you start a bottleneck, if I understood him correctly. What I do know is my heirlooms germinate fast! I can save back seeds for next year! and they taste good.

If a strain is already considered pure, it would seem that "open pollenation" would be like inviting all the local "junk yard dogs" to your kennel when your best purebred female is in heat.

Unless as Jekylnz said, you could somehow confine your best plants within the same bag with a handful of bees, and hope that they cross pollinate. Not likely.

I would speculate that a quarter million seeds from a single plant should provide plenty of "diversity".

 

[deluxestogie]

Using the corn example earlier of 200 plants earlier, to keep diversity; a quick search says an ear of corn is from 600-800 kernels (seems high but ok). Presuming the larger number is true, and one viable ear per cornstalk, that would be 160,000 seeds to maintain "diversiy". A single tobacco seed head presuming 250,000 seeds would be the equivelant of planting 312 corn plants.

Bob is much more knowledgable than I, but just making a simple comparison based on numbers.

Corn, like most grasses, must be pollinated from other plants in the stand, usually wind pollinated.

Your 250,000 corn seeds are a collection of all seeds from 200 plants, and you would plant 0.125% of them to replace the 200 plants. With 200 tobacco plants, the number of seeds would be in the range of 50,000,000 seeds--an astounding number--of which you would plant only 0.0004% to replace the 200 tobacco plants.

Bob