There is al lot of mis information on saving seeds. Most of the plants like tomatoes and peppers are hybrids. Saving seeds and planting the next year you may get one of the parent plants and not the hybrid plant. Some of the hybrids are exempt from this problem like sweet 100 cherry tomatoes. Most plants like zucchini squash will produce original plants the nest year. Radishes beets and other root crops should produce plants like the originals.
I always recommend never to save seed from tomato plants even if they are heirlooms. Heirlooms will produce original plants, however we have certain diseases that are transmitted through the seed. Mosaic virus is one. Should you save seed and plant the next spring and you have the virus in the seed, your plants will show no signs of the virus until about 6 weeks of age. When this happens it is usually to late to start over for that spring and you will have to buy plants for that spring. I personally never save seed because of this problem.
- Mike Stanton