I've been studying flax (Linum usitatissimum) and arbuscular mycorrhizal fungi (AMF).

Lots of data still rolling in, but I can share a few things.

Flax is known to by highly mycorrhizal. Its been fun to look at infected roots...I've never seen such high colonization. The dark blue structures are AMF.

I've seen that it takes at least 1 month of growth from seed for the roots to become colonized. This depends on fungal loads in the soil and on root development. Roots that are about 1 mm in diameter are big enough to support lots of infection.

In AMF experiments, we use fungicde to suppress the AMF so that we have a non-AMF control. I treated soils with fungicide every two weeks for 4 months, and I still see active AMF in treated soils and roots.

This is interesting because farmers frequently ask me about fungicide effects on beneficial soil fungi. It turns out that AMF are pretty tough!

I don't know yet what it takes for flax to boost AMF loads in the soil to provide a benefit to the subsequent crop, but that's where this research is headed.

Thanks to @Ameriflax for supporting this research, to the farmer cooperators, and to my diligent lab tech, Michael, who has stained A LOT of roots!