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Does Canada have enough genes in the bank?

Currently, more than 80 percent of the collection consists of heritage and Canadian-bred varieties, meaning there may not yet be enough genetic diversity in the collection for Canadian breeders to tap into it in a meaningful manner. “Certainly, our potato genetic resource program is not large,” admits Dr. Ken Richards, the manager of Plant Gene Resources in Saskatoon, Saskatchewan. “Our collection is not as large as those of the United States or at the International Potato Centre (CIP) in Peru, but it was designed to capture and preserve heritage potatoes that have been grown in Canada.” Breeders have access to US or Peruvian collections to incorporate germplasm into their programs to get the desired genetics they want, he adds.

It takes time and resources to build a collection of potato germplasm and it is also an ongoing process to manage the collection. Unlike grains that can be stored dry and only need to be grown out periodically, potatoes have to be grown regularly. The collection also must be disease free and, therefore, before a variety can be stored in the collection, it has to be tested for disease and virus incidence and, if infected, cleaned of them. In any given year, about 10 per cent of the collection is in clonal form and the remaining percent of varieties is maintained
in vitro.

Garrett Pittenger works with Seed of Diversity, an organization that preserves Canada’s seed heritage. He has donated numerous heritage potato varieties to Potato Gene Resources because he wants to ensure the collection is diverse and useful. He says that, because many heritage varieties have been preserved, it is now possible for breeders, growers and consumers to enjoy potatoes that had fallen out of favour but are now making a comeback. “We are now appreciating the purple or blue varieties for their anti-oxidant properties,” Pittenger comments. “We may need to ‘re-commercialize’ some of the heritage varieties because growers will grow them if there is a market.”

However, without Potato Gene Resources some of the varieties might no longer exist. Pittenger would like to see niche markets developed, which will help preserve Canada’s potato heritage rather than leaving all the work to Potato Gene Resources and a handful of dedicated potato preservationists.

Nevertheless, the issue of the number of varieties in the collection is less critical than the variability of the genetics in the collection. Richards explains that, by their nature, potatoes do not have a great amount of genetic variability. Unlike a cereal crop, which may have a wide rage of genetic variability, potatoes have many similar DNA characteristics. “Breeders need to be aware of this when they are selecting clones for breeding purposes,” Richards continues. “They need to be selecting genetic material that is not close to the genetics they are working with.” He cites the Irish potato famine as an example of the close genetic relationships between varieties. The Irish farmers were growing varieties genetically uniform and susceptible when a pandemic of a disease, late blight, wiped out the potato crop of Europe and North America.
This phenomenon is commonly called genetic vulnerability. Two factors influence the degree of vulnerability: the relative areas devoted to each variety and the degree of uniformity or relatedness between varieties. “It is only possible to improve genetics within the limits of the material that is available,” Richards explains.

To this end, Potato Gene Resources has a good collection of varieties adapted to the Canadian climate, but breeders may need to access varieties from CIP or the United States in order to increase the genetic diversity within their programs. Fortunately, he adds, Canada’s breeders do frequently go to these other collections to access traits that might not be available in Canada’s “bank.” With a growing emphasis on breeding varieties that have specific traits, such as drought tolerance or disease resistance, there may be a limited amount of germplasm in the world to achieve the desired goal due to the narrowness of the genetic variation in the crop as a whole. Even though there are red, blue and white potatoes, and some are round and others are long and narrow, their invisible DNA could be very similar.

Meanwhile, Pittenger believes that Canada’s collection of potato clones needs to be protected so it is available to breeders to learn about traits that may not known or are yet to be appreciated or needed “I think the missing link is that more of the potato clones need to be in the seed potato system and then evaluation of the varieties could be beefed up so we know what we have,” Pittenger suggests. “Because most of the materials in the gene resources collection are adapted to Canada,” Dr. Richards continues, “it could become more valuable in the near future because we may have to start breeding to meet the challenges of climate change.” He says he would like to see a screening test developed to evaluate the collection for drought tolerance, which would be added to the list of traits that is available for each clone in the collection.

In the end, the number of clones in the collection is not the real issue. The difficulty is maintaining a collection that is well suited to Canada, but that may not have the diversity of genetics that is really needed to breed the varieties that are required by the industry. Support from the seed industry and growers would not only increase the knowledge of the many heritage and Canadian varieties that are held in the collection, but could also be of assistance in maintaining a more genetically diverse collection of seed stock.