Clonal propagation and quick detection of virus-free plants of sweet potato, Ipomoea batatas

Sweet potato feathery mottle virus（SPFMV）viral infection of tuber surface of edible sweat potato, Ipomoea batatas causes chapped and cracked band symptom called russet crack-like symptom（RC-LS） , and the RC-LS depreciate commercial value and has become a severe problem in agricultural production. This project was undertaken to establish large quantities of virus-free sweet potato from the shoot apex and suckers of the plant using clonal propagation, and to develop a rapid and precise detection method using reverse transcription-polymerase chain reaction（RT-PCR） . The culture of shoot apexes less than 0.3-1.0 mm in size brought plant regenerating rates of 82% and 65% using Komamine and Nomura（1998）medium and Murashige and Skoog（1962）medium, respectively. The results of RT-PCR of RNAs from plants obtained from shoot apex culture and plants of SPFMV sufferer showed that SPFMV virus was clearly removed by shoot apex culture conducted in this study. For clonal propagation, 80-100% of suckers from stems of the virus-free plants detected grew into complete plants after 6 weeks of culture, indicating that the virus-free plants could be routinely propagated 5 times by the short circle. The sweet potato produced in field show no symptom of RC-LS even after two seasons.