Just in case we blow up mother earth, the Svalbard Global Seed Vault on the island of Spitsbergen, which is 600 miles from the North Pole has all the plant seeds to start over again.

The Svalbard Global Seed Vault was financed and built by Norway. The vault will be operated by the Global Crop Diversity Trust. The capacity of the vault is about 2 billion seeds.

The seeds are kept at minus 4 degrees. For some of the seeds this may keep them usable for more than 1,000 years.
Let's hope we never have to go into the Svalbard Global Seed Vault to get the seeds to start over.
More details on USA Today, Wikipedia and Croptrust.