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New Zealand Plant Protection 64 (2011): 160-167

Cultivar decline in sweetpotato (Ipomoea batatas)

S.L. Lewthwaite, P.J. Fletcher, J.D. Fletcher and C.M. Triggs

ABSTRACT

The sweetpotato (Ipomoea batatas) crop is propagated vegetatively by field transplanting adventitious sprouts produced on storage roots retained from the previous season's harvest. This system promotes the persistence and accumulation of both viruses and spontaneous mutations. A phenomenon known as cultivar decline has been reported internationally, where the root yield and appearance of commercially grown sweetpotato cultivars appear to deteriorate over successive growing seasons. The relative contributions of virus infection and plant mutation to cultivar decline are uncertain, but both issues are addressed through the use of virus-tested tissue cultured propagation systems. This study assessed the degree of decline for cultivars 'Owairaka Red' and 'Beauregard' within the New Zealand biophysical production environment. Storage root yield decreased significantly with increasing field exposure, for both cultivars (P<0.001). The general appearance of 'Beauregard' roots deteriorated with greater field exposure, but the appearance of 'Owairaka Red' showed no significant change (P<0.001).

Keywords: kumara, disease, virus, mutation, micro-propagation.

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