Suspicious ring in cut rhizome - Fusarium Wilt?

[WhiteRabbit]

Today, I decided to tackle a repot and dividing of a No I.D. Onc. alliance inter-generic.

Leaves have (likely) fungal spots on older growth - this one does grow outside year-round, and I suspect it is too damp and cold in winter, causing the spots. Otherwise, the plant looks good! Big, green, plump, and firm pbulbs. Good looking new growth.

But after cutting the rhizome, I noticed the ring...

Last year, I had another Onc. inter-generic, going downhill with growths rotting - when I went to cut off the affected pbulbs I noticed a ring in the rhizome - tho much worse looking than the ring in this plant's rhizome. Asking here on the board, fusarium wilt was suggested as the culprit, and a link to an orchid diseases page did seem to confirm that. (That plant was trashed -that post and pix here: http://www.orchidboard.com/community...me-please.html)

This ring is not nearly as bad looking as the plant last year, and plant otherwise seems healthy (tho you can see there is root rot - I have been watering this frequently with the recent extreme heat, so that's possibly the cause, but could also be caused by fusarium) but I am afraid it may be fusarium ...

What say you all?

I don't want to waste potting media if the plant is likely to croak (I might pot one or two of the divisions to see how it goes, but trash the others).

I could cut further into the rhizome, to see if there is any free from the ring, but I took a few small divisions from the outer perimeter of the plant, and all show the ring.

Thanks for your help!