Answer: It sounds as if they have become infected with some type of bacteria or fungus. Open wounds allow easy entry for disease. Did you use sterile tools and a soilless potting mix, as well as dust the cuts with a fungicide before planting? It's also a good idea to let the cuts callus in the open air for at least several hours or a day after dusting with fungicide before planting. This helps seal the cut. Finally, the tuber must have some existing roots as a rootless section can not produce new roots and will just die. I hope this info helps.
Q&A Library Searching Tips