By Clet Wandui Masiga, Conservation Biologists, Geneticist and Farm Entrepreneurs

The genome of cultivated sweet potato contains Agrobacterium T-DNAs with expressed genes. This is an example of a naturally transgenic food crop. This conclusion was reported by Kyndt et al in May 2015 in a peer reviewed original research article published by PNAS.

The experiments conducted by this group found out that two different T-DNA regions of Agrobacterium rhizogenes and Agrobacterium tumefaciens  are present in the cultivated sweet potato (Ipomoea batatas [L.] Lam.) genome and that these foreign genes are expressed at detectable levels in different tissues of the sweet potato plant. The experiment involved 217 genotypes that included both cultivated and wild species.

Accordingly the researchers concluded that their findings indicate that sweet potato is naturally transgenic. Sweet potato being a widely and traditionally consumed food crop, could affect the current consumer distrust of the safety of transgenic food crops.

In the authors own statements they indicate the significance of the study as follows:
We communicate the rather remarkable observation that among 291 tested accessions of cultivated sweet potato, all contain one or more transfer DNA (T-DNA) sequences. These sequences, which are shown to be expressed in a cultivated sweet potato clone (“Huachano”) that was analyzed in detail, suggest that an Agrobacterium infection occurred in evolutionary times. One of the T-DNAs is apparently present in all cultivated sweet potato clones, but not in the crop’s closely related wild relatives, suggesting the T-DNA provided a trait or traits that were selected for during domestication. This finding draws attention to the importance of plant–microbe interactions, and given that this crop has been eaten for millennia, it may change the paradigm governing the “unnatural” status of transgenic crops.