A call on our Clemson University Your Day radio program today had me thinking about tomato pollination again. Do they self-pollinate, the caller asked? "Can I save seeds from heirloom tomatoes" was a follow-up question.
Tomatoes are variable -- my later Google searches reminded me. Yes, breeders have tried to develop varieties that self-pollinate rather than requiring pollination. But, what I remembered about greenhouse varieties needing sonic vibration or bumblebees for pollination (and good fruit production) was right, too.
Bees definitely visit tomato flowers in the garden, so if you're wanting to save seeds of a particular open-pollinated variety, certainly, many seeds will result from self-pollination (there are lots of seed in a single tomato, derived from fertilization from multiple pollen arrivals), but there may be cross-pollinated seeds, too, in the mix.
To ensure a single variety, you can always bag a cluster of flowers, shaking them (gently) during flowering to make sure that pollination occurs, and collect seeds from those fruit.
It was interesting that we had a number of calls from folks wanting to save seeds from their vegetable gardens, and at least one caller wanting to avoid GMO seeds (they're not at this point available for purchase by home gardeners, so aren't really a current concern), although many excellent seed companies make it seem like it's a possibility in their catalogs and websites.
I posted on the topic of seeds (GMO, open-pollinated, and hybrids) in mid-February.
It's interesting that I'm getting pieces from seed companies (via being a member of Garden Writers Association), clarifying seed origins this spring, and we're getting calls asking about GMO's and seed saving.