Proper plant population for seed preservation

[sandbar]

In anticipation of our impending move to the farm this summer, we are greatly expanding our market garden and making plans for a large (for us) grow-out of tomato, pepper, bean, squash, melon, cucumber and eggplant varieties. As I plan the garden, I realize it is going to take a significant amount of room and I'm trying to determine just how much space I really need. We have all the space we'll ever need, but I need to tell the row-crop acerage renter how much space he'll be losing this year.

Depending upon whom you listen to, the recommendations for properly preserving a particular variety (let's take tomatoes for instance) range from 8 or 16 plants to 20 or so for in-crossing types and 5 times that (100 plants) for out-crossing types.

I am planning on selling some of the seed commerically through my own on-line store and, of course, trading with the good folks on this board. I am primarily looking to supplement my income with a business that is mainly active (selling-wise) during the non-growing season ... so, that's why I looked at seeds.

I was hoping to grow out about 60 tomato, 30 pepper, 10 bean, 5 eggplant, 15 squash, 10 melon and maybe 4 cucumber varieties. My goal is to maintain these varieties in a personal seed bank, trade/sell them and grow different varieties next year.

So, for the above listed crops, how many do you believe is necessary to properly preserve a particular variety?

[sandbar]

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[PatrickW]

Okay, I'll take a stab, but really I'm not an expert on this. If someone else offers conflicting advice, pay attention to them.

Especially with inbreeding plants what's more important is ensuring you don't get any off types. For example, with a tomato, it's very possible to save from a single plant. It's just really important the plant you pick doesn't have any off taste or other problems. To this end, it's important to keep good records of what you do to ensure if you do get customer complaints or discover an off type yourself years later, you can track down where it came from and destroy that stock of seeds. When thinking about how many plants to grow, consider how many you may need to pick from in case one of your plants is not suitable for seed saving. For tomatoes, 5-10 plants at the most??

For peppers it's probably a similar approach, but since they are a little more out-breeding maybe save from a few plants, and weed out off types before they have a chance to cross pollinate with the others.

For beans you can never save all the seeds you need from a single plant, so the number of plants you have will probably be determined by how much seed you need. Really, you should do some selection on your plants. You should identify which are the most productive or otherwise of best quality, and only save seeds from those. I would plant twice as many as you think you need, and weed out the least productive or least desirable.

For squash, you'll probably hand pollinate. In this case, even though they are out breeding, you only need two plants (or one if you self it). Again, I would grow enough to be able to select out off types, but you don't need that many really.

For the others I'm not really sure.

Do you have a book on the subject? Suzanne Ashworth, Seed to Seed is a good reference book for this kind of thing.

[canadamike]

If you want to save seeds, in or out-breeders, it is always good to rely on more than one plant. One plant cannot bring as much diversity as many, that is a simple fact. I tend to forget what is ''minimaly doable'' to look at a larger picture. Sorry, natural inclination...

But if you want an amazing vining zucchini, I have a fantastic and really delicious one from Korea, totally unknown, I got it from GRIN, called JEWEL GREEN. It is a vining one, and to me vining veggies, in a reality of urban gardeners loaded with chain link fences or other ones, anyway, is the way of the future.

It is very productive, does well under low light and cold and is also the favorite of the guests I entertained last summer at home. And the earliest I ever grew, stopping production once frosts sets in.

And it comes with an added bonus: it starts to fatten at around 10-12 inches, can get bigger than most before the cooked center of the fruit becomes watery ( i.e. firmer flesh) and the size when it fattens makes it perfect for stuffed zucchinis. By the time the regular ones get as fat as Jewel Green, they are so long you are cooking big boats

[ottawagardener]

Eh, Eh Michel. Whatcha say? I like this Jewel Green vining zuke that you speak of. Expect pm shortly.

[ottawagardener]

For squash etc... I've heard about 20 plants is the amount needed.
Tomatoes: several, let's say at least 10
Peppers: these do cross pollinate. There's some confusion on that but I'll go with what Patrick said.

Other than that, I've read what you've read.

[bunkie]

i have read all the above info and used many of these ideas myself. can't add anything more. are you going to sell on-line sandbar, ie is your store on-line?

michel, i totally agree about connecting vining plants, city fences and all that! i was just reading about a girl named Novella and her boyfriend who are 'urban farming' on a plot in Oakland California. she wrote the book 'Farm City: The Education of an Urban Farmer'. she made great use of her fenced in areas....and the fences!

Jewel Green's got my attention too telsing...pm sent also to michel...

[Dan]

i sent a PM earlier, this sounds fantastic. i have to talk to Jim about growing these over at his place.

[hiven]

Seed to seed recommend 20 plant for cucubitas, but Koanga institute (NZ) suggest 6 to 8 plants for good vigour.
I find 20 plants a bit too much and opt for 6 to 8 plants however make sure you use 3 to 6 male flowers for (hand) pollinations to keep their wide gene pool.

Brassica, I used 20 or more plants. Due to space and isolation issue I only save smaller brassica (such as oriental ones) and leave the cauliflower/broccoli/heading cabbage out.
You can grow more then 1 type of brassica without getting crossed pollinated by use caging method though.

Pepper/tomatoes/aubergines, I used 4 to 6 plants.

beans/peas, I used 5 to 20 plants.

Beet (either beetroot or chard) and spinach, I use minimum 6 plants.

Lettuce and chicories, I use minimum 5 plants.

Alliums, i use minimum 15 plants.

All the above infos were from several sources, good luck !

[PatrickW]

All of this depends a little too on how you will do your isolation, and if or how the plants will be cross-pollinated.

For example if you grow 30 different kinds of peppers in the same area, how are you going to isolate them? If you isolate them by distance, this will probably depend a lot on your own experiences and the insects present in your garden. You can also look this up in a book to get some general ideas. Like Telsing said, there's a lot of confusion and disagreement over promiscuity of peppers. My guess however is you will need an awfully big piece of land to keep that many isolated with distance, especially if you expect to sell the seeds, in which case you will probably be thinking of higher standards than a home gardener.

If you don't isolate by distance, then you probably need to either think about temporally or with insect barriers. Temporally would mean only planting one variety at a time, or the number you could isolate with distance.

If you use an insect barrier, then you need to think about if and how the plants are going to get cross-pollinated. Most gardeners isolate individual plants, so there is no cross pollination and seeds are only saved from the single plant. For most people's purposes this is enough. However, if the plants don't cross pollinate, the resulting seeds will still only be from an individual plant. If the seeds are saved from an individual plant, they can still have problems from a gene pool that's too small and develop inbreeding depression. In other words, if you have 10 plants of the same variety, none of which cross pollinate, you save seeds from them all, all you end up with is a mix of seeds but not a gene pool mix. If you again save seeds from the resulting plants, you are still only going from one plant to the next and and not maintaining any breadth in the gene pool. Like I said, for most people's purposes, this is okay.

If you feel you need to do something to promote cross pollinating between the peppers, you have a couple of options. You could hand pollinate or use alternate day caging. Alternate day caging means you have a removable cage for each variety, then open the cage for one variety at a time to let the insects in. This is of course assuming you do experience cross-pollinating in your garden. Once again however, for peppers, inbreeding depression is not usually considered an important problem, so really most people don't get into this.

If you then decide, okay, even though they don't cross-pollinate, it would still be a good idea to have a mix of seeds from the same variety. Perhaps you decide 10 is a good number. If you are a seed company, think about how many other seed companies are selling the same variety. For every other seed company out there, or even other home gardeners, there will be someone else saving seeds from that same variety from a different plant. Surely for any given variety in your garden, there will be at least 10 others growing it, that you could get seeds from if you really needed to. If you are really maintaining something special or rare, then you might think about maintaining more than one plant yourself. Even if you do save seeds from more than one plant, you don't have to plant them all the same year, you can do them 1 or 2 at a time over a number of years.

If you think about this in terms of squash. When plants cross pollinate, only two plants are involved. You can grow 100 squash plants, but any seed you get from them will be the result of either a plant pollinating itself, or two plants crossing. There are no other possibilities. Indeed, if you only grow one or two squash plants every year and keep replanting those seeds, this would be a bad idea. Selfing a plant in particular is not always a wise thing to do. However, if in 2010 you plant 2 squashes or 100 squashes, you hand pollinate to ensure a controlled cross, any seeds you save will be of comparable quality. In order to ensure you have enough plants to maintain your gene pool you will need to think about from one year to the next, where your seeds came from and if you are in total crossing enough plants. In this case, you don't need to make yourself crazy. Selfing plants sometimes is okay as is replanting seed saved from the previous year, but you do want to maintain as much gene pool depth as possible over time.

This is why when talking about tomatoes, I say only one plant is really necessary. Nearly all OP tomatoes grown today are from uncrossed seeds saved from one generation to the next. Mostly this is no problem, but off types do pop up from time to time. If you have a very rare tomato, you only save seeds from one plant, and an off type shows up, undetected until after you have discarded your old stock of seeds, then you have a real problem. If however a very common tomato is what's at issue, you can just discard your stock and get fresh seeds from someone else. If you are saving from more than one plant (for example 10), it can actually complicate things, because you statistically have a higher chance of saving an off type, and if you do get an off type only 1 out of 10 of your seeds will be bad.

[PatrickW]

Actually I'll just follow up on what I just said with another example with squashes.

Suppose you plant 100 of the same variety of squash, isolate so crossing with other varieties is not an issue.

If you then save 100 seeds from a single squash, and replant them and save seeds the same way year after year, you will have a problem.

This is because seeds saved from a single squash can only occur from self pollination or a cross between two plants. This means, even though you think you are saving seeds from 100 plants, you are only saving seeds from one or two.

Maintaining a gene pool is more than just thinking about how many plants to grow in a single season...

[sandbar]

Thanks for everyone's input. Sorry, I didn't respond earlier ... have been busy at work.

Firstly, I do have Ashworth's book which is where I obtained most of the information regarding incrossing and outcrossing population suggestions.

Patrick, I do understand what you are saying when I save seed from a single tomato plant. I'm only preserving the genetics of that one plant. My impression to the value of saving seed from a larger population of plants (culling the off-types, first) was that it would minimize the impact of any off-type characteristics.

Using your example of saving seeds from 10 plants, if I did manage to save seed from one off-type plant (taste, color, etc.), then the amount of "off-type" seed would be 10% rather than 100% if I saved only seed from that one plant. So, when I think about preserving a variety's genetics, I think about a large population of plants that would safely allow me to preserve desired genetics (by saving fruit from only true-to-type plants) even though some plants may not grow true-to-type. In other words, I am planting a larger population expecting that some plants may need to be rogued out to ensure I get good seed.

Am I making myself clear as mud?

Thanks again,
Steve.

[sandbar]

Hiven, that was very helpful information ... thanks!!

Bunkie, store is not on-line, yet. Haven't spent the time to put it up since I don't have anything to sell, yet. Another summer project ...

Michel, you have my attention!! I will get in contact with you as soon as I finalize my planting plans ... hopefully this weekend.

[sandbar]

Jan 17, 2010 13:17:50 GMT -5 ottawagardener said:

Peppers: these do cross pollinate. There's some confusion on that but I'll go with what Patrick said.

With squash and cukes, I know I'll be hand pollinating and then bagging.

With beans, I didn't feel that Ashworth clearly addressed the issue of cross pollination. I'm not sure whether it needs some protection, or just minimal isolation from an adjacent variety. Guess I need to do some more research here.

Peppers: Is bagging an acceptable method to maintain seed purity? I will be growing close to 30 types of peppers (hot and sweet) and would prefer not to have to construct cages (time and money issues).

Tomatoes: Was planning to only bag the potato leaved varieties.

Additionally, I was planning to alternate species within a row ... say tomato, pepper, brassica, tomato, pepper, brassica, etc. to keep one species from intermingling too much within the row. I am thinking of spacing the rows 8' to 10' apart since I won't be able to stake all the tomato plants. Some of each variety will be staked and the rest will sprawl.

[PatrickW]

Jan 21, 2010 21:33:27 GMT -5 sandbar said:

Patrick, I do understand what you are saying when I save seed from a single tomato plant. I'm only preserving the genetics of that one plant. My impression to the value of saving seed from a larger population of plants (culling the off-types, first) was that it would minimize the impact of any off-type characteristics.

Using your example of saving seeds from 10 plants, if I did manage to save seed from one off-type plant (taste, color, etc.), then the amount of "off-type" seed would be 10% rather than 100% if I saved only seed from that one plant. So, when I think about preserving a variety's genetics, I think about a large population of plants that would safely allow me to preserve desired genetics (by saving fruit from only true-to-type plants) even though some plants may not grow true-to-type. In other words, I am planting a larger population expecting that some plants may need to be rogued out to ensure I get good seed.

Steve, It all depends on what your needs and expectations are. There aren't really any right or wrong answers. It also depends on what insects are present in your particular garden.

If you are a 'real' seed company, selling standard seeds and competing against other larger seed companies, you may very well decide that 10% off types in your seeds is simply too much. In this case you may be better off saving from only one tomato and making sure it's okay.

If you are a hobby gardener, have created your own variety for your own purposes, then the approach you suggest of saving from 10 plants to ensure against loss in case an off type develops might be better.

Really this whole subject is an issue of life long learning, and it's the reason why Ashworth's book is vague in places, because sometimes you just don't know.

There's a grey area between bagging and caging, and they both should work. Ben of Real Seeds has a good system for pepper plants that involves a little more work at the beginning, but in the long run is probably simpler than bagging:

www.realseeds.co.uk/isolation%20cages.html

Again, it really comes down to your particular needs. If you only need a small amount of seeds, on a one-off basis, then bagging is certainly the way to go.