There's some pretty neat stuff we've recently found with regards to growing plants in martian regolith. Interestingly, the problem with perchlorates isn't necessarily apparent right away. Mark Watney would have likely been able to grow potatoes, just really shitty ones. The second part of the problem shows up when you eat the potatoes and the perchlorates fuck your thyroid up.

There are some pretty neat ideas in terms of bioremediation, though, like growing nitrogen-fixing plants like alfalfa to add nitrogen, growing water hyacinths to draw perchlorates out, or using bacteria for both of these things. A big wrinkle though is that the heavy UV levels on mars may affect some of these chemicals in ways that make them more troubling to plants, bacteria, and people alike. Just really hoping for a sample return soon so we can get some truly accurate simulants to grow in.