Abstract:
The sweet potato (Ipomoea batatas Lam) is a major staple food in many parts of the world. Sweet potato leaves
and tubers are consumed as food and livestock feed. Biotic and abiotic stresses affect yield leading to a reduction
in production. This review analyzes factors limiting sweet potato production and the progress made towards
stress tolerance using genetic transformation. Genetic transformation could enhance yield, nutritional value and
tolerance to stress. Transgenic sweet potatoes tolerant to biotic and abiotic stress, improved nutritional value and
higher yields have been developed. Sweet potato expressing the endotoxin cry8Db, cry7A1 and cry3Ca genes
showed lower sweet potato weevil infestation than non-transformed lines. Transgenic cultivar ‘Xushu18’
expressing the oryzacystatin-1 (OC1) gene showed enhanced resistance to sweet potato stem nematodes. Sweet
potato line ‘Chikei 682-11’ expressing the coat protein (CP) exhibited resistance to the sweet potato feathery
mottle virus (SPFMV). Transgenics expressing the rice cysteine inhibitor gene oryzacystatin-1 (OC1) also
exhibited resistance to the SPFMV. Transgenic cultivar ‘Kokei’ expressing the spermidine synthetase gene
FSPD1 had higher levels of spermine in the leaves and roots, and displayed enhanced tolerance to drought and
salt stress. ‘Shangshu’ variety expressing the IbMas has shown enhanced tolerance to salt stress. Transgenic
‘Lixixiang’ expressing IbMIPSI showed an up-regulation of metabolites involved in stress response to drought,
salinity and nematode infestation. Transgenic ‘Yulmi’ sweet potato transformed with copper/zinc superoxide
dismutase (CuZnSOD) gene showed an enhanced tolerance to methyl viologen induced oxidative and chilling
stress. Similarly, transformation of cultivar ‘Sushu-2’ with betaine aldehyde dehydrogenase (BADH) gene
resulted in transgenics tolerant to salt, chilling and oxidative stress. Sweet potato varieties ‘Kokei14’ and ‘Yulmi’
transformed with the bar gene were shown to be tolerant to application of the herbicide Basta. The development
of stress tolerant varieties will immensely increase the area under sweet potato production and eventually
promote the adoption of sweet potato as a commercial crop. Sweet potato research and breeding for stress
tolerance still faces technical and socio-political hurdles. Despite these challenges, genetic transformation
remains a viable method with immense potential for the improvement of sweet potato.
