A brief perspective published in Science on August 3, written by Dr Brande Wulff of the John Innes Centre in Norwich, UK and Dr Kanwarpal Dhugga from Mexico’s International Maize and Wheat Improvement Centre, has highlighted some of the barriers that have led to wheat becoming “an orphan among genetically-modified (GM) crops” (1).
Devastating diseases, such wheat blast ― a fungus that recently emerged in 2016 in South America and has since become a huge contributor to crop loss ― or the equally destructive stem rust found in Kenya and Ethiopia, pose a threat to global food security. The authors suggest that the discovery and isolation of disease-resistant genes in wild versions of wheat would present an opportunity to produce blight-resistant wheat cultivars. In other words, inserting blast-resistant genes found in wild wheat varieties into the genome of commercial wheat crops could significantly delay the rise of pesticide-resistant pathogens.
Wheat is one of the few crops that remains unmodified. The main reason for this may be the pushback from anti-GM consumer groups ― mostly in Europe and Japan ― as well as the costs associated with purchasing GM seeds, resulting in unattractive profit margins for farmers. Wheat generates around just 20% of the farm income that maize generates, which would make it difficult to recover the research-associated costs required. This seems to be why this important worldwide staple has lagged behind and the transgenic modification of wheat has remained a low-priority.
Other GM crops ― maize, soybeans, and cotton ― are commercially available and have been shown to significantly improve the profit margins of farmers. Although not yet commercially available, rice crops that have been genetically modified to be insect resistant, herbicide tolerant, and biofortified with provitamin A are approved for use. Whereas, only a single application previously sought approval in the US for a herbicide-tolerant wheat produced through genetic modification, and the request was swiftly abandoned in 2004.
The crop improvement efforts that gave rise to modern high-yielding wheat cultivars are also what has made this cereal extremely susceptible to disease. By concentrating on genetic strains that combine the most desirable traits, the resulting genetic homogeneity has led to greater vulnerability to pathogens. Methods like crossbreeding commercial crops with wild pathogen-resistant varieties of wheat could promote greater genetic diversity and disease resistance. However, cross-breeding is a time-consuming process, moreover, sexual incompatibility can hinder progress.
Furthermore, exploiting single resistance genes in problem areas is risky, since pathogens can evolve into new more dangerous strains, which deters most breeders from employing this method. Therefore, the authors suggest “the genetic treasure trove for disease resistance in wild relatives of wheat remains a largely underutilized resource in wheat breeding.” Countries in Africa and Asia which often face food security concerns are likely to be most amenable to adopting GM wheat.
Whatever your stance on GM crops ― whether you are in support or vehemently object to genetic modification ― food security is an ever-growing concern as the global population continues to increase, and will likely need to be solved using a variety of creative agricultural strategies.
(1) B.B.H. Wulff and K.S. Dhugga. Wheat—the cereal abandoned by GM. Science (2018). DOI: 10.1126/science.aat5119