Saving seeds, avoiding inbreeding depression

[DavidP]

I've been saving seeds for a few years now with pretty good success and the resultant plants look and seem pretty OK.

I read in the book "Seed to seed" by suzanne ashworth that for inbreeding species like tomatoes you need to take seeds from about 20 individuals to really maintain enough genetic variation over time to provide a decent population in the long term. I really am not doing that in that I don't think I've ever grown 20 plants of one single variety.

Is this something I should be worried about and perhaps I should really just be buying seed instead from suppliers who hopefully are maintianing the diversity by using 20 or more plants as there seed source. I know at the moment its probably not much of a concern in a generation or so. I if I keep doing this from a small number of plants will I eventually run into a general deterioration of the variety that I'm trying to save.

I guess I probably shouldn't worry too much as perhaps I should just periodically buy new seeds to get a better gene pool into my seed collection. I'd be interested in any experiences of a variety declining in successive generations and what peoples thoughts were who got much more experience than I do as I've only really been saving seeds for a few years and with no problem as yet.