b'ENHANCING HEAT TOLERANCEThe information about the 55 varieties can be helpful to growers and breeders. Farmers can consider the relative heat tolerance and sensitivity of the different varieties when choosing potato varieties for their farms to reduce the risk of heat-stress impacts on their crops, says Li. Also, he says the varietal data could be used by potato breeders who want to include heat-tolerant parents in their breeding programs.Lis current research includes several studies to understand and improve heat tolerance in potatoes. One study is looking into why tuberization is particularly sensitive to heat stress, which genes and physiological signals are involved, and what can be done to change the activity of these genes and signals so the plants will have good tuber production even when the weather is hot. We already have a good idea of which genes are probably playing a major role in heat tolerance with respect to tuber growth, he says. Once we identify the genes and complete our study of the underlying biology of heat stress, then we may be able to develop ways to make the plants more tolerant to heat stress. This study is exploring both genetic and non-genetic approaches to improve heat tolerance. For the genetic component, Li and his team are interested in trying to develop heat-tolerant variants of todays most popular processing varietiesLeft: Potato plants grown under optimal conditions. Right: Potato plants grown using a technique called somatic cell mutation.under heat-stress conditions.PHOTO: AAFCThere are a few varieties, such as Russet Burbank, that are very important for the potato processing industry. The industry has developed processes and equip- A CALL FOR ACTION ment for processing these specific cultivars, so it is not easy for them to frequentlyLi emphasizes the critical need to develop effective heat-proofing solutions for Ca-switch to different cultivars, he explains. If we can induce variants of the genesnadian potato production. Some people might think that climate warming would that cause sensitivity to heat stress to make these cultivars more heat tolerant,be an advantage for potato production in Canada. They assume potato varieties then the industry can continue to use these cultivars.would behave in their usual way or perhaps even have better yields if the climate The researchers are hoping to collaborate with industry on this work becauseis warmer and the growing season is longer. But we found that is not necessarily each company has its own variety requirements.the case. For the studys non-genetic component, the researchers want to develop prac- Li believes the Canadian potato industry could be more vulnerable to effects tices that growers could use to minimize heat stress during the growing season iffrom heat stress than potato production in some warmer regions. the weather turns unexpectedly hot. They would also like to work with industry onSome warmer countries that produce potatoes actually grow two crops per year, this component. he explains. They plant potatoes in the fall or early spring and harvest the tubers Li and his team have some thoughts on possible non-genetic practices. Forbefore the hot summer arrives. They grow different types of crops in the hot summer. example, perhaps the activity of the genes responsible for heat tolerance could beIf their growing conditions are hotter, they can just harvest the tubers a little earlier induced by spraying a substance on the crop or by exposing the crop to a certainbefore the temperature becomes too high for the potato crop. But in Canada, our type of light. The idea here is if the weather forecast predicts high temperatures,growing season is too short to use that two-crop system, so the potato crop has to then a grower could apply such a treatment to activate the relevant genes a fewpass through the stressful hot summer in order to get harvested in the fall. days before the predicted hot spell to make the plants better prepared to deal withCurrently we can still grow potatoes successfully in Canada. But what if the heat. The researchers are just starting some preliminary tests on their ideas. one summer we have a hot spell with several days above 35 C, what can we do? Another one of Lis studies is looking at the effect of high temperatures on theWe would face a dilemma: to harvest or not to harvest. If we harvest too early, maturity of 50 Canadian potato varieties, comparing the same high-temperaturethe tubers will not be sufficiently large and will not have good enough quality. If conditions and ideal conditions that were used in their earlier study. The resultswe do not harvest, then heat stress will damage the tubers and seriously reduce from this research could provide crucial information for breeders and growers.yields and quality. Or the tubers could stop growing and then start regrowing One of the most important attributes that growers consider when selectingwhen the temperatures become more suitable, and that secondary growth could a potato variety is the varietys days to maturity. But what if high temperaturesalter tuber shape.change the varietys maturity? It takes a long time to develop new potato varieties, Li says, and even somatic If the maturity changes, that immediately affects many things: when thecell mutation approaches require a number of years for development and testing. farmer can harvest; whether the tuber quality and yield at this different harvestGovernment, industry and university researchers must work together to proactively date will meet the farmers expectations; whether the differences in quality willaddress heat stress in Canadian potato production, he adds. affect the processing industrys ability to process the tubers; and whether theHopefully, we can find some effective solutions before conditions become too differences in the tubers will affect the quality of the end-product. hot, so we can help the Canadian potato industry to continue to be competitive.46 SPUDSMART.COM WINTER 2020'