Fungus in soil (?) stunts my rose....at least I think

[elfa]

I have a rose that just won't grow. I dug it up today and there is a whiteish substance in the soil.

See photos:

I have no idea of what this is, but it doesn't look helpful. Any ideas about it is and what to do when I encounter it in the future.

thanks

elfa

[Ewa Szulc]

I can see long brownish spot on the stem (??) have a look at those pictures of different desease of roses and look if you see similar symptoms