Effective communication on preserving crop diversity
This talk by Cary Fowler, on the Global Seed Vault at Svalbard, is worth watching both for the content and as a model for effective public speaking. For that reason, I've categorized it under "careers in science" as well as "agriculture." Note the lack of bullet-point slides!
[Note added 9/11: text slides can make presentations boring, but handouts of text slides help students focus on understanding rather than scribbling notes. So I'm going to cut down on text slides in talks at meetings, but not necessarily in guest lectures to undergraduate classes.]
It's worth noting that even dry, frozen seeds may lose viability in storage. (You could probably still recover DNA, but that's only of practical value for the few traits, if any, whose value can be identified from DNA sequence alone.) So it's good to take seeds out of storage and grow fresh seed periodically. Usually, you want to do this in a way that minimizes natural selection in the seed-increase environment, to avoid losing traits that were useful where the crop was grown originally. For example, you want plants far apart enough that tall plants don't shade shorter neighbors enough to keep them from producing seed. And you don't want plants that were particularly prolific in the seed-increase environment to be over-represented in your next stored sample. Preserving crop diversity is a vastly under-funded activity, although that is true of most areas of agricultural research without immediate links to short-term profit.
Although even a few stored seeds can be multiplied enough in a few years to deal with slowly developing problems, such as climate change, if there's a global wheat epidemic you need at least enough disease-resistant seed on hand that one cycle of seed multiplication will meet farmer needs for the next growing season.