A nuclear weapon in the arsenal against plant pathogens

Something new under the sun… Ug99 Resistant Wheat

Earlier this month, reports heralded a promising solution to an international threat to our wheat crops. The biological arms race between plant pathogens and crop species has been escalating for centuries. Since humans are heavily invested in the success of our favorite food plants, we have done what we can to give plants the edge. For most of human history, this has involved traditional breeding, selecting for naturally resistant varieties that still maintain the best food crop qualities of the plants. More recently, we have been able to aid plants with more sophisticated technology. I’ve written before about how transgenic (aka genetic engineering or GMO) technology is proving useful for proving resistance for some food plants where the timescale of traditional breeding and other control measures just aren’t going to work out in the plants (and therefore our) favor. Today, I’d like to talk about a different example that does not involve combining genetic material from different species. Nevertheless, this technology involves ‘nuclear weaponry’ of sorts to alter the genetics of plants.

The recent trend of gluten-free diets notwithstanding, wheat is still one of the world’s most important staple crops. It is grown on more acreage worldwide than rice and maize (remember, that’s corn). It is the ingredient in the most basic of foods- bread. It’s our amber waves of grain, the ultimate imagery of nutritional bounty.

Wheat fields via wikipedia

However, there is a significant plant disease called wheat stem rust that can decimate beautiful wheat fields. The spores of this fungus are spread by the wind making control problematic once an infestation begins. Wheat varieties spawned from the ‘Green Revolution’ by Normal Borlaug offered robust resistance for thirty years. However, a new variety of wheat stem rust appeared in Uganda in 1999 that could infect even these varieties. Named, Ug99, this plant pathogen ranks at the top of the international ‘worry list’ for problems with crop yields and food security.

Wheat stem rust via wikipedia Close-up of stem rust (”Puccinia graminis”) on wheat.
Photo by Yue Jin. [http://www.ars.usda.gov/is/graphics/photos/jun04/k11192-1.htm Image Number K11192-1] {{PD-USGov-USDA-ARS}}

This month a new breakthrough has been reported in the host-pathogen arms race to give wheat the edge over this fungus. Miriam Kinyua, a researcher at Eldoret University in Kenya, in collaboration with FAO/IAEA joint laboratories used radiation to induce mutations in wheat seeds popular with Kenyan farmers. This treatment results in genetic mutations in the seeds. The plants from these seeds were subsequently screened for resistance to Ug99. Eight new Ug99-resistant varieties were identified, and two were officially approved as varieties by the national committee of the Ministry of Agriculture. Earlier this month Kenyan farmers were invited to Eldoret University for a two-day agriculture fair to highlight new technologies and debut the new wheat varieties. Seeds from these varieties will be available to farmers for the next planting season.

These new varieties come at a pivotal time when Ug99 seems poised to become a bigger international threat to Europe’s ‘breadbasket’ in the Ukraine and Kazakhstan. Their genetic material is critically important for farmers in Africa, where Ug99 is prevalent. I’d like to use this scenario as an example case for gauging public opinion on the implementation of plant genetic technology. How do we as a society balance the time-critical demands of the Ug99 threat with safety concerns over new wheat varieties?

I’m intentionally framing this argument in parallel with those related to the GMO crop debate. Just to be explicitly clear- radiation-induced mutation breeding is NOT considered GMO. It is the result of changes to the wheat genome without any introduction of genes from other organisms. However, in the realm of plant genetics, I would argue that this kind of genetic manipulation (radiation-induced mutation) would be considered ‘genetic engineering’ because humans have indeed manipulated the wheat genome in unnatural ways. Given this premise, how do we as a society move forward with this technology? Should there be a universal standard for safety and efficacy for crops that covers ALL new plant varieties (new hybrids, naturally-occurring mutants, radiation-induced mutants, GMO)? Should these new Ug99-resistant varieties be labeled in any special way?

In the case of the new varieties produced by irradiation, we do not know the underlying reasons for their Ug99 resistance. Do you think it is important that we know all of the details before putting it into agricultural production? For now, it’s enough for scientists to know that these new varieties are resistant, but you’d better believe they aren’t going to stop there. Of course, scientists will continue to look for new Ug99-resistant varieties, but I’m sure these lines in particular will be the focus of studies to dissect exactly how they are resistant. If scientists can understand the mechanism, it will be easier to translate this resistance into other wheat strains or cereal crops for which this kind of fungal pathogen is a problem.

What kinds of safety testing, if any, do you think is necessary? There is a high probability that the radiation-induced mutation resulted in the expression of an altered protein (which we don’t know). Mutant versions of proteins could be potential allergens or toxins. What about long-term effects on human health and the environment? Should we wait for a few more decades of testing on these varieties before putting them into agricultural production?

Full disclosure: I have not been able to determine what kinds of testing these new wheat varieties have undergone as far as safety is concerned. The articles that I have read have only focused on Ug99 resistance. Presumably, the yields are just as good or these lines would not have gotten to field trials. It is completely possible that some, all or none of these kinds of testing have been conducted on these varieties.

Finally, as an extreme viewpoint, are these new wheat varieties so completely unnatural that they don’t even have the right to exist? Should we just destroy them? Should African wheat breeders rely on conventional techniques only? Should we just learn to not eat wheat?

My main point in this series of questions is not really to justify GMOs or skate around the issue of their regulation. In the case of plant biotechnology, the science has far outpaced the ethics and legal system that should create boundaries for it. Also, at the same time there is a lot of money at stake because agriculture and the food industry are big business. While the science may seem more fluid, society certainly has a right to step in and draw arbitrary boundaries for ethics and legal purposes. The point is that we should be having these kinds of open discussions to create a better framework for regulation rather than relying on a retrofitted patchwork system that’s not really designed to deal with these new technologies.













2 thoughts on “A nuclear weapon in the arsenal against plant pathogens

  1. Lkf

    Good questions. I disagree, however, that society has a right to make “arbitrary” boundaries. Choices should be made only after thoughtful study. There is too much at stake for the world’s food sources to be limited by rigid ideology.

    1. johnnaroose Post author

      Yes, but for legal purposes, there are lots of what I would call ‘arbitrary’ boundaries- even though they have some data to back them up. Things like age cut offs for sexual consent, draft age, drinking age, legal definitions of adult or child. There’s nothing particularly magical about any of these as precise boundaries for any individual, but over a population those limits make sense. Many things exist as a continuum, but lines have to be drawn for enforcement purposes. This is kind of the water we’ve waded into with a lot of modern biotechnology. One would hope that decisions would be made based on facts, but humans tend to have a lot of baggage when it comes to bias.


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