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In search of the magic bullet for CPB


September 25, 2009
By Dan Woolley

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Agriculture and Agri-Food Canada potato research scientists in Fredericton, N.B., are confronting a big challenge.

Agriculture and Agri-Food Canada potato research scientists in Fredericton, N.B., are confronting a big challenge.

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Researchers with the BioPotato Network are attempting to transfer genetic resistance to Colorado potato beetle from South American wild potatoes to domestic potato species.

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As members of the BioPotato Network, they are attempting to transfer genetic resistance to Colorado potato beetle from South American wild potatoes to domestic potato species.

The AAFC Fredericton scientists have been working with the wild Solanum species for insect resistance for the past 15 years.

The problem, explains Dr. Yvan Pelletier, a BioPotato Network research partner, is that most South American Solanum species are diploid genetically, meaning each of their cells has two sets of chromosomes. Meanwhile, domestic potato varieties are usually tetraploid with four sets of chromosomes in each cell.

This means crossbreeding for insect resistance has to focus on tetraploid wild species or use diploid domestic potatoes, explains Dr. Pelletier, adding that somatic fusion is another genetic transfer option, but it involves a very long process and is difficult to achieve.

Another challenge the researchers face is the day length when the six South American wild varieties being study in Fredericton tuberize. According to Dr. Pelletier, as the wild varieties are from tropical regions in the southern hemisphere, where the duration of day is always around 12 hours, they begin to tuberize at the end of summer. This is too late for them to complete their development in much cooler and darker Atlantic Canada.

Nevertheless, scientists using seed from an American gene bank have started the South American potatoes in a greenhouse and then transplanted them to plots at the AAFC Fredericton Potato Research Centre.

Despite significant hurdles, AAFC potato researchers have succeeded in hybridizing three new potato species, two of which they intend to study further to see if they have resistance to Colorado potato beetle. Dr Pelletier says researchers will use an internal pesticide study to determine the exact chemical composition of the hybrids leaves, after which they will determine the active agent found within the hybrid leaves’ that works against Colorado potato beetle.

Scientists are using a new spectrograph to extract the chemicals mixtures, which can also identify 400 different compounds to speed up their identification of the desired compounds, explains Dr. Pelletier.

Ultimately, BioPotato Network scientists hope to create a topical bio-pesticide to apply to the foliage of potato varieties that are not resistant to Colorado potato beetle by using the compounds from CPB-resistant hybrid potatoes. That is, if they are easy to extract, says Dr. Pelletier.

It is also hoped the chemical compounds are not glycoalkoloids, which are expensive to extract from plant tissue and “impossible to synthesize” as a pest control product, adds Dr. Pelletier.

Even if and when the researchers make their big discovery, the federal Pest Management Regulatory Agency (PMRA) will have to approve and register any bio-pesticide developed by the BioPotato Network before it can be marketed, says Dr. Pelletier.

The network’s current research will conclude in 2011.


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