I'm also new to seed saving, but I've been reading a lot on the subject. As I understand it, there are a few ways for small gardeners to avoid inbreeding depression.

The seed you save this year can be planted with other seeds you obtain elsewhere. If you want to keep the variety pure, of course the new seeds have to be the same variety.

Otherwise, you could plant another squash of the same species, and let it cross. REALIZE: THIS WILL RESULT IN FRUITS DIFFERENT FROM THE ORIGINAL! That's important to many gardeners, and something they don't want. But it keeps many of the genes you want in the population. In future generations, save seeds from the fruit most like the Shishigatani.

Whether you obtain new Shishigatani seeds, or breed with another variety, save more seeds than you'll plant each year. When you plant, plant a mix of newer and older seeds. Genes lost in the last season might be regained this way. Be sure to plant seeds grown elsewhere at least every few years. Sure it takes many plants to maintain a healthy population... but who says they all have to be in YOUR garden?

So maybe you aren't growing your saved seeds exclusively, but you're still saving money. And you're adapting the population to your garden; when you save seeds from the healthiest plants, the genes that don't work for you die out.

If purity IS important to you, keep your Shishigatani seperated from other squash of the same species, either by distance, or by pollen barriers, if you're willing to hand pollinate.

Purity is definitely important to me. Would it be possible to save seed from one of these squash and plant more than one next year from that seed? I know that's inbreeding, but would it suffer that much?

I've been reading other sources that say pumpkins/squash don't really show any symptoms from inbreeding.

Say I could get two seeds to germinate, produce, and save seed from two different squash, would that be enough genetic diversity to avoid any problems in the long run?

Thanks!

The longer you inbreed, the greater chance of inbreeding depression. But I'd save what you can and plant it, but I'd watch for decreased vigor, or any other signs of inbreeding depression. Breeding in new material at any point should alleviate it. Doing so before depression shows up can avoid it.

Just don't be afraid to try. Until you try, you never know what you can accomplish.