Improving Potato Stress Tolerance and Tuber Yield Under a Climate Change Scenario - A Current Overview

Abstract

Global climate change in the form of extreme heat and drought poses a major challenge to sustainable crop production by negatively affecting plant performance and crop yield. Such negative impact on crop yield is likely to be aggravated in future because continued greenhouse gas emissions will cause further rise in temperature leading to increased evapo-transpiration and drought severity, soil salinity as well as insect and disease threats. This has raised a major challenge for plant scientists on securing global food demand, which urges an immediate need to enhance the current yield of major food crops by two-fold to feed the increasing population. As a fourth major food crop, enhancing potato productivity is important for food security of an increasing population. However, potato plant is highly prone to high temperature, drought, soil salinity, as well as insect and diseases. In order to maintain a sustainable potato production, we must adapt our cultivation practices and develop stress tolerant potato cultivars that are appropriately engineered for changing environment. Yet the lack of data on the underlying mechanisms of potato plant resistance to abiotic and biotic stress and the ability to predict future outcomes constitutes a major knowledge gap. It is a challenge for plant scientists to pinpoint means of improving tuber yield under increasing CO₂, high temperature and drought stress including the changing patterns of pest and pathogen infestations. Understanding stress-related physiological, biochemical and molecular processes is crucial to develop screening procedures for selecting crop cultivars that can better adapt to changing growth conditions. Elucidation of such mechanism may offer new insights into the identification of specific characteristics that may be useful in breeding new cultivars aimed at maintaining or even enhancing potato yield under changing climate. This paper discusses the recent progress on the mechanism by which potato plants initially sense the changes in their surrounding CO₂, temperature, water status, soil salinity and consequently respond to these changes at the molecular, biochemical and physiological levels. We suggest that future research needs to be concentrated on the identification and characterization of signaling molecules and target genes regulating stress tolerance and crop yield potential.

Keywords: drought; high CO2; high temperature; photosynthetic yield potential; potato; salinity; stress tolerance; yield.

FIGURE 1

A schematic diagram illustrating the photosynthetic carbon assimilation and its export to the potato tuber sink. In the chloroplast, light harvesting complexes absorb sunlight and generate ATP and NADPH through photosynthetic electron transport chain. The ATP and NADPH are then consumed by Calvin cycle to assimilate carbon to simple carbohydrate, triose phosphates (triose-P). Triose-P is either used to synthesize starch in the chloroplast or exported to cytosol in exchange for Pi through triose-P/P_i translocator. In the cytosol, the triose-P is then converted to sucrose via hexose phosphates using key sucrose biosynthetic enzymes, cFBpase and SPS. Sucrose is then transported to the sink (tuber), where it is converted to starch by AGPase. The synthesis of sucrose in the cytosol generates P_i which is exported to the chloroplast in the exchange for triose-P. Any stress that inhibit sucrose synthesis and its transport to sink (tuber) results in the feedback inhibition of photosynthesis due to P_i regeneration limitation. The broken arrows indicate the stress sensitive processes. RuBisCO, ribulose-1,5-bisphosphate carboxylase/oxygenase; RuBP, ribulose-1,5-bisphosphate; TPT, triose phosphate translocator; cFBPase, cytosolic fructose bisphosphatase; SPS, sucrose phosphate synthase, AGPase: ADP glucose pyrophosphorylase. Modified from Hüner et al. (2016).

FIGURE 2

A simplified model for the processes involved in the conversion of solar incident energy to final plant biomass and associated energy losses. Out of 100% solar incident energy the C₃ photosynthetic organisms are capable of converting only 4.6% to final plant biomass, suggesting a maximum theoretical energy conversion efficiency of 0.046. Most portion of solar energy is lost resulting in considerable decrease in energy conversion efficiency between the solar energy and final plant biomass. Redrawn from Zhu et al. (2008, 2010); and modified based on Dahal et al. (2014a,b).