Late blight disease is a major constraint for potato farmers, costing an estimated US $3-$10 billion per year globally. In Uganda, where about 300,000 smallholder farmers grow potatoes, the disease can destroy as much as 60-100% of a potato crop. Farmers use fungicides to control late blight, but because the cost of those agrochemicals commonly represents from 10 to 25 percent the value of a farmer’s potato harvest, their use significantly reduces family incomes, whereas their application poses risks to human health and the environment.
Over the years, breeders have crossed potatoes with wild relatives to produce highly late-blight-resistant varieties, but those varieties often lacked other traits that people wanted, so adoption was limited. Breeders have had better luck crossing cultivated clones with resistance to the disease, which has produced varieties that combine late blight resistance with high yields and flavor and cooking traits that consumers demand. However, the pathogen’s rapid evolution can leave those varieties less resistant over the years, and many farmers are happy to grow varieties with little or no resistance to the disease if there is a strong market for them, even if it means they need to spend a significant portion of their earnings on fungicides to ensure a good harvest. CIP scientists have thus taken a new approach – using transgenesis to transfer resistance genes from potato wild relatives into potato varieties that are already popular with farmers and consumers.
CIP partnered with Uganda’s National Agricultural Research Organisation (NARO) to test a biotech version of the popular variety Victoria that contains a stack of three resistance (R) genes. Confined field trials conducted at NARO’s Kachwekano Zonal Agriculture Research Institute showed that the 3R-stack Victoria is highly resistant to late blight, surviving exposure to the pathogen while it destroyed conventional potatoes plants nearby. In 2017, CIP and NARO began collaborating on a compulsory assessment of possible risks to human health or the environment that is required by Uganda’s National Biosafety Committee. Confined fields were established and initial trials completed near Fort Portal (Rwebitaba), Mbale (Buginyanya) and Kabale (Kachwekano).
Marc Ghislain, CIP Program Leader for Game-Changing Solutions, explained that once several seasons of field trials have been completed in three locations, NARO will present the results to Uganda’s National Biosafety Committee as part of a request that the biotech version of Victoria be released to Ugandan farmers. If released, Ghislain predicts that it will greatly benefit smallholder families through better harvests and lower production costs, without the health and environmental risks that fungicides pose.