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Sweet Potato with a Side of Virus

11/20/2012
Megan Scudellari

More than 30 known viruses threaten sweet potato crops, but South American researchers are fighting back, sequencing these viral genomes to keep the vegetable on your Thanksgiving menu.


Whether it’s mashed, baked, or cooked into a pie, the sweet potato you plan to enjoy this Thanksgiving is one lucky spud, because it avoided destruction by a host of viruses that infect sweet potato crops around the world each year.

The sweet potato is one of the most important root crops worldwide and one of the most common subsistence crops in developing countries because of the plant’s hardy nature.

The sweet potato is one of the most important root crops worldwide and one of the most common subsistence crops in developing countries because of the plant’s hardy nature. Source: Wikimedia Commons, Llez





Yet bacterial, fungal, and viral diseases plague sweet potato crops, the latter of which are considered the most difficult type of infection to manage. More than 30 known viruses infect the plant, often in assaults of two or three viruses at a time. These “mixed” infections can cause leaf curling and yellowing, stunted growth, and plant death.

In the last year, several research teams in South America have made a concerted effort to understand the genetic diversity and evolution of sweet potato viruses. Their findings highlight the important role of mixed infections in the evolution of these pathogens, and could help scientists breed virus-resistant sweet potatoes.

In 2012, researchers at the National Agricultural Technology Institute (INTA) in Argentina sequenced the genome of sweet potato virus G (SPVG) for the first time (1). “The study of this virus may be useful in understanding its spread around the world, and maybe it will give us a clue of where the virus originated,” said Liliana Di Feo, a researcher at the Institute of Plant Pathology at INTA who led the research.

The virus was isolated from Argentinean sweet potatoes infected with multiple viruses. Di Feo’s team now plans to study the effect of single viral infections to determine how individual viruses affect crop yields.

A team at Embrapa Vegetables, a government agricultural research company in Brazil, published the full genome sequences of 34 sweepovirus isolates sampled from a sweet potato bank and commercial fields in Brazil (2). They compared those sequences to pre-existing sequences of 67 sweepovirus isolates. The data provided evidence that recombination events occur within sweet potato plants, as viruses swap DNA amongst themselves. This genomic exchange has led to the emergence of new sweepovirus species, the authors wrote. They also found that the genetic diversity of sweet potato viruses in Brazil is greater than previously thought.

The Argentine team, however, found that their sweepovirus did not cluster with the other South American isolates, but appeared to be more closely related to isolates from Africa and China, said Di Feo.

References

1. Rodriguez Pardina, P.E., N. Bejerman, A.V. Luque, and L. Di Feo. 2012. Complete nucleotide sequence of an Argentinean isolate of sweet potato virus G. Virus Genes. doi:10.1007/s11262-012-0784-z.

2. Albuquerque, L.C., A.K. Inoue-Nagata, B. Pinheiro, R.O. Resende, E. Moriones, and J. Navas-Castillo. 2012. Genetic diversity and recombination analysis of sweepoviruses from Brazil. Virol J, 9:241.