Whether planting for survival, or maybe you just like having a home garden to enjoy fresh vegetables, having necessary garden supplies on hand is important as well as starting with the right seed. Not all seeds are created equal.
Hybrid seeds are produced from cross-pollinated plants. Hybrids are produced to improve characteristics of resulting plants . These characteristics might be:
Planting seeds from a hybrid for the original sowing does not ensure using the seeds from their fruit will see the same traits passed along. And, in some cases the next generation plants will be less favorable.
GMO (Genetically Modified Organism) refers to the laboratory process where the genes from the DNA of one organism are transferred to an unrelated animal or in this case plant.
The methods used can be described an 'imprecise' and 'unpredictable' possibly resulting in unintended changes.  These changes can affect :
Toxic / allergic effects
Lower crop yield
Unintended environmental effects
Traditional Seeds (Old-fashioned seeds)
Using traditional or open-pollinated seeds allows you to save seeds from the fruit or vegetable so that the harvested seeds can be used from one year to the next. Allowing plants to open-pollinate also means they will develop characteristics that allow them to better survive in their local area. 
The saving of seeds to use for planting next year is a process in itself where you want to avoid cross pollination of different varieties, use proper cleaning and storage methods for the seeds harvested. For more information on home survival gardening check out Mini Farming: Self-Sufficiency on 1/4 Acre
Building a 'brown bag' of traditional seeds for next year means you need to start with good seeds that can be harvested for next year's planting. To that end, the seeds you use should be open-pollinated, organic and non-GMO.
There are several companies whose seeds fill the bill. Some of the better known ones are listed below.