April 2012. Sweet potato roots in New Caledonia grown in rather sandy soil showed galls on the surface. what are they?

The concenus among members was that the galls were those of the root-knot nematode, Meloidogyne sp. However, the common species do not cause galls on sweet potato as shown in the image. Even on the roots they produce only slight swellings, which are not always detectable. Symptoms can differ with different nematode species and different vareties of sweet potato. Slicing through the root tissues should show the swollen, round female nematodes with the naked eye although staining with acid fuchsin or methyl blue will make it easier. If nematodes are producing the large galls on tubers in your photo, you should find many swollen females in each gall.