A record of choices
Every cross in a lineage was somebody choosing one plant over several hundred others. The line that results is a compressed account of those choices, and of the traits that were worth the years it took to fix them.
Where lines go quiet
Commercial attention narrows. Lines that were widely grown a decade ago can become difficult to find, and the knowledge attached to them tends to disappear faster than the material does.
Preserving diversity is partly a bet that a trait nobody currently wants will matter later. It is not a sentimental position. It is the only position available, given that the alternative is deciding now which possibilities to close.
A line nobody is asking for today is the only kind of line that can answer a question nobody is asking yet.
