Merging Physiological and Genetic Approaches to Improve Abiotic Stress Resistance

Abstract

There is ample evidence for global warming and resulting climate change. To sustain food production in view of climate change, we need to improve resistance to abiotic stresses in commercially desired cultivars. Using potato as an example, a strategy is illustrated for such improvement by merging physiological and genetic approaches. Potato (Solanum tuberosum L.) is a cool-season crop, cultivated in the temperate zone in North America, Europe, and the highlands of South America, Africa, and Asia. In these areas, frost is often a major factor limiting potato production. Climate change models predict erratic weather patterns including more severe and untimely frost episodes. Cultivated potatoes are highly frost sensitive and are often killed when tissue temperatures fall below −3°C. Several wild potato species are frost tolerant. These species carry two desired traits: 1) They can survive temperatures as low as −6°C while growing under normal conditions (NAFT), and 2) they are able to acclimate in response to chilling temperatures and increase frost tolerance and survive at temperatures as low as −12°C (CAC). These two important traits are lacking in cultivated potatoes. We have demonstrated that NAFT and CAC are genetically distinct traits that must be selected for individually and combined in a desired genotype. By precise screening for both NAFT and CAC, we have been able to select frost-hardy clones of potato that also carry commercially desired traits. This progress was made possible by understanding the physiological and biochemical mechanisms of frost survival and cold acclimation. We have shown that: 1) plasma membrane ATPase is an important site of cellular response to temperature stress, and this response appears to be mediated by changes in cellular/membrane calcium and changes in membrane lipid composition; 2) specific lipid composition changes occur in the plasma membrane that allow a plant to acclimate to cold and increase freezing tolerance, and an increase in the degree of unsaturation of specific lipids is important in this acclimation process. We have further shown that these changes in lipid are associated with an increased expression of Δ9 desaturase gene during cold acclimation; 3) calcium can mitigate the impact of heat, cold, and salinity on potato. In addition to NAFT and CAC, freezing avoidance is an important trait for plant survival. We have been able develop frost-hardy carrot hybrids by combining freezing tolerance in the top with freezing avoidance in the root. Taken together, our studies provide a systematic approach to improving abiotic stress resistances of crop plants and suggest strategies for developing production practices to mitigate the impact of abiotic stresses in a changing climate scenario.