GrainsWest Fall 2019

Tech 2019 grainswest.com 43 BY IAN DOIG • ILLUSTRATION BY JASON LIN composed of organic matter, are biodegradable. With questions around human health and the environment satisfied, hopes for proving the technology’s effectiveness in crop protection are high. As well, RNAi technology does not involve a transgenic element, and so it would not be subject to GMO regulations. SMITING SMUTS AND BUNTS As a tool to control weeds and crop pests, RNAi is selective, targeting only the genes responsible for individual traits in the target fungus, weed or insect. While broad-spectrum chemicals may impact unintended targets, the specificity of RNAi min- imizes the possibility. It can’t be completely ruled out that an RNAi fungal treatment may affect the soil microbiome but fungi and humans have very different genetic pathways, making such interaction impossible. Agriculture and Agri-Food Canada (AAFC) research scientist John Laurie works at the Lethbridge Research and Development Centre, where he’s leading a three-year RNAi seed-treatment project funded in part by the Alberta Wheat Commission (AWC). When GrainsWest spoke with Laurie in June, he acknowledged RNAi technology has generated a great deal of interest, but cau- tioned that this project is just starting. Nonetheless, even before work had begun, his lab had been contacted by multiple compa- nies interested in the eventual commercialization of the results. The project aims to develop a seed coating that will suppress smuts and bunts using nanocarrier-complexed RNAi. The process utilizes cell-penetrating peptides, which are short chains of ami- no acids able to pass through cell membranes. These are used to piggyback RNA into the cells of the target organism. During germination, plants are vulnerable to infection by pathogens. From this treatment, the seed will receive disease protection as well as having its own genes modulated to promote development at the seedling stage. Laurie likens the process to a person wearing gloves to avoid picking up cold germs from a door handle. “We’re putting a bio- degradable, non-toxic glove on the seed. It would essentially be to make the seed resistant or to block the infection.” If germination is like passing through a doorway, when the seed wears its RNAi gloves, it enters the next stage of its life without becoming infected by the microorganisms lurking on the metaphoric door handle. This is a time of great interest in the soil microbiome that sees scientists studying the activities of microorganisms that assist plant growth. Toxic, broad-spectrum fungicides have proven a double-edged sword in this underground realm in that they elim- inate both beneficial bacteria and fungi as well as their undesir- able cousins. Laurie noted that where farmers have switched to organic practices, the smuts and bunts that plagued agriculture prior to the 1900s, have reappeared. “We want to facilitate the next generation of microbiome related seed technologies,” he said. “To do that, we probably have to get away from these fungicides, which means smuts and bunts will immediately become a problem.” Using the specificity of RNAi to shut down the infection pro- cess of the smut or bunt, the treatment Laurie intends to develop is expected to have zero impact on beneficial soil organisms. Additionally, the plant’s gene expression can be tweaked to strengthen its relationship with these beneficials. FIGHTING FHB Like Laurie, AAFC Saskatoon Research and Development Centre research scientist Steve Robinson said the development of RNAi technology may represent a widespread change in agronomic practice. He is heading an ongoing project develop- ing RNAi sprays to combat sclerotinia in canola but primarily Fusarium head blight (FHB) in wheat. Robinson described the initiative as complementing breeding projects whose aim is to create resistant crop varieties. “This is a parallel strategy to develop ways to mitigate persistent and potentially devastating diseases,” he said. The project is now working in the lab to identify candidate FHB genes that can be targeted using RNAi to produce a formu- lation that can control the disease in the field. Robinson’s team is mining the genomes of the pathogens that cause sclerotinia and FHB for potential target genes. Measuring changes in gene expression during the infection process in both the wheat and the FHB pathogen, they have identified promising genes. In a two-pronged attack, they intend to kill the bulk of the FHB infec- tion while silencing genes involved in DON production, halting or limiting the production of the mycotoxin. Again, the advantage over non-specific broad-spectrum fungi- cide is the RNAi spray’s ability to target only FHB pathogens and not beneficial soil microorganisms while completely biodegrad- ing within weeks. The study is now focusing on Fusarium grami- narium but Robinson said by tweaking the design of the spray, it could tackle a multitude of FHB-related pathogens. Just over a year into this three-year project that will likely be followed up with another three-year phase, Robinson said initial results are promising. He explained, however, that any resulting FHB treatment won’t be available to farmers for years. Once the final product is demonstrated to be non-toxic, it must be tested in field trials. This will require scaling up production of RNA that is now produced through fermention by bacteria that produce RNA molecules. Importantly, this is a formerly expensive process that can now be done for considerably less. Convinced RNAi truly is the next big thing, Robinson emphasized the technology has to prove viable. “It’s got to be as effective as the sprays available to producers now to stand any chance.” If positive lab results can be duplicated in the field, AAFC would search for an industry partner to negotiate regulatory hurdles and commercialization. Robinson added that crop input companies are taking the potential of RNAi technology seriously. Given there is no great philosophical problem in getting these non-transgenic products to market, once it can be demonstrated there is profit in producing them, they should take off.