Variability of Storage Root Yield, Size, and Shape of Sweetpotato Mericlones

Viruses and mutations can accumulate through vegetative propagation of sweetpotato resulting in reduced yield and quality. It is recommended that growers purchase foundation seed roots so that production fields are no older than three to four generations.  Foundation seed production begins with using virus-tested (VT) plant stock maintained in vitro. A VT plant is derived from meristem tip culture and the resulting plant is tested on a virus susceptible indictor plant. If no symptoms are found after several rounds of testing, it can be declared VT. Many meristem tip cultures are done for a given variety with expectations that some still possess demonstrable viruses. The process of removing viruses from plants via meristem tip culture may introduce changes in phenotype due to mutations or somaclonal variation. The objective of this research is compare in field trial yield, shape, and trueness to type for a number of mericlones for several varieties. Results showed most mericlones were not variants and thus redundancy was reduced in the tissue culture collection by eliminating some mericlones. Several mericlones did appear less robust and off-type and not suitable for using as a parental source for foundation seed.