At first sight I prefer to diagnose microscopical eel worms (nematodes); see Pratylencus scribneri and perhaps Pratylenchus jordanensis - which are responsible for this kind of lesions, provided that other animals can be excluded.

My initial recommendation would be to cut all these damaged roots away and treat the bulb with an appropiate nematicidal agent. Phosphorous organic agents with systemic properties should be helpfull.

But please note: This is a preliminary answer only - may be a more concise one will follow.

Hans-Werner