Microtuber formation in potato callus

Abstract

Potato callus has been shown to be capable of de novo organized development including shoot and root formation. A surprising finding in a study of potato (Solanum tuberosum cv. Iwa) callus culture initiated from leaf explants on a medium supplemented with auxin and cytokinin is reported here. Five weeks after callus formation, a low frequency (about 10%) of the callus cultures had formed microtubers. The microtubers initially appeared to be light green and some were elongated. One week later the microtubers had lost much of the green appearance and were full of hairs on the side and with many scattered dark brown spots on the top view. Histological analysis showed that a microtuber was connected with the callus and not with the leaf explant as the callus typically lacked the internal organization of a leaf. This is the first report of the occurrence of microtubers in potato callus cultures.