Seed sharing (between farmers) and seed saving (storing for sowing in a later season) are possible with all traditional seed varieties, as opposed to hybrid seeds.
Traditional seeds (also called heirloom seeds) are open-pollinating varieties and not hybrids. These seeds produce plants which in turn reproduce to provide seeds which are true to their parents. Unlike hybrids, these seeds can be ‘saved’ for another crop, and by sensible plant selection, a farmer can keep improving his stock of seeds with every passing season.
Traditionally, besides saving their own seeds, farmers also had a system of barter or exchange where they shared their seed stock with each other. With the introduction and use of hybrid seeds, these practices have also seen a gradual dying-out and require to be revived to ensure conservation of the many seed varieties indigenous to India which otherwise may be lost forever.