Gas-exchange, water use efficiency and yield responses of elite potato <i>(Solanum tuberosum</i> L.) cultivars to changes in atmospheric carbon dioxide concentration, temperature and relative humidity

AbstractIn spite of the agricultural importance of potato (Solanum tuberosum L.), most plant physiology studies have not accounted for the effect of the interaction between elevated carbon dioxide concentration ([CO2]) and other consequences of climate change on WUE. In 2010, a first controlled environment chamber experiment (E1) was performed with two treatments: one control at a [CO2] exposure level of 380ppm and the other at elevated [CO2] first to 700ppm and subsequently to 1000ppm. Plants grown at elevated [CO2] levels of 700 and 1000ppm showed a consistent significant increase in leaf level photosynthetic water use efficiency (pWUE) by stimulation in net photosynthesis rate (62% and 43% increase of An) with coincident decline in both stomatal conductance (21% and 43% decrease of gs) and leaf transpiration rate (19% and 40% decrease of E) resulting in pWUE increments of 89% and 147%. Furthermore, the ratio of leaf intercellular [CO2] to ambient air [CO2] (ci/ca) remained unchanged among treatments. In 2011, a second experiment was performed (E2), where two treatments comprised [CO2] levels of 380ppm (control) and elevated of 1000ppm. The plants were subjected to three temperature levels (14, 21 and 28°C). This procedure provided for investigation of WUE dependence of temperature at different [CO2]. At leaf-level, a consistent increase in pWUE of 28% across the three temperature levels was observed, caused by a significant stimulation in net photosynthesis rate (16%), and a significant decreased stomatal conductance (25%) with a simultaneous drop in transpiration rate although not significant. The ratio ci/ca was in contrast to the first experiment significantly higher in plants grown at elevated [CO2]. Despite this photosynthetic acclimation, concurrent stimulation of aboveground and belowground biomass accumulation was observed at elevated [CO2], resulting in higher harvest indices and irrigation WUE (45%), not significantly different from the increase of pWUE. Out of four cultivars investigated, the largest increase in irrigation WUE was found in the cultivar Ballerina, which also showed a six time increase in tuber yield, perhaps indicating less overall inhibition of photosynthesis by sugar accumulation. At all temperature levels, WUE was significantly larger at high [CO2]. This was the result of increased net photosynthesis rate (at low temperature), decreased transpiration rate and stomatal conductance (high temperature) or a combination of those two responses (moderate temperature). The results signify that beneficial effects of potato plant cultivation at elevated [CO2] comprise increased WUE at various temperature levels, but due to acclimation of photosynthesis the increase was smaller during prolonged than stepwise exposure. The experiment also showed that, in the conditions of climate change, associated higher T could decrease the response of photosynthesis to higher [CO2] and higher vapor pressure deficit will decrease the gain in WUE

Cytosolic glutamine synthetase is important for photosynthetic efficiency and water use efficiency in potato as revealed by high-throughput sequencing QTL analysis

KEY MESSAGE: WUE phenotyping and subsequent QTL analysis revealed cytosolic GS genes importance for limiting N loss due to photorespiration under well-watered and well-fertilized conditions. ABSTRACT: Potato (Solanum tuberosum L.) closes its stomata at relatively low soil water deficits frequently encountered in normal field conditions resulting in unnecessary annual yield losses and extensive use of artificial irrigation. Therefore, unraveling the genetics underpinning variation in water use efficiency (WUE) of potato is important, but has been limited by technical difficulties in assessing the trait on individual plants and thus is poorly understood. In this study, a mapping population of potatoes has been robustly phenotyped, and considerable variation in WUE under well-watered conditions was observed. Two extreme WUE bulks of clones were identified and pools of genomic DNA from them as well as the parents were sequenced and mapped to reference potato genome. Following a novel data analysis approach, two highly resolved QTLs were found on chromosome 1 and 9. Interestingly, three genes encoding isoforms of cytosolic glutamine synthase were located in the QTL at chromosome 1 suggesting a major contribution of this enzyme to photosynthetic efficiency and thus WUE in potato. Indeed, Glutamine synthetase enzyme activity of leaf extracts was measured and found to be correlated with contrasting WUE phenotypes. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1007/s00122-015-2573-2) contains supplementary material, which is available to authorized users

Potato tuber gene expression in starch metabolism throughout tuber bulking.

<p>SAGE tags were mapped to genes encoding enzymes involved in starch metabolism. Tag counts per million (y-axis) for multiple enzyme isoforms catalyzing a single step were summed. Desiree is shown in red, Jutlandia in blue and Kuras in green. The error bars indicate standard error of measurement. Numbers on x-axis indicate weeks after planting. Left side of the hatched bars: 2008; right side: 2009. The asterisk symbol indicates gene expression values significantly different than the gene expression of the two remaining cultivars (p-value<0.05). The solid reaction arrows indicate the major metabolic route of high carbon flux leading to starch accumulation. The hatched lines indicate minor metabolic routes where carbon flux is limited. The red hatched box indicates the G1P transporter suggested by Fettke and coworkers and discussed in this study. The green solid line indicate cell membrane, the yellow line indicates the amyloplastic membrane.</p

Sample statistics.

<p>Total number of DeepSAGE tags determined for each library for Desiree, Jutlandia and Kuras cultivars. Data are represented for all three biological replicates for each time point: 9, 12, 15, 18 and 21 weeks after planting (2008) and 9 and 11 weeks after planting (2009). Combined tag counts of biological replicates are also presented. The last columns represent the tuber yield in hkg/ha and starch content of Jutlandia, Desiree and Kuras cultivars.</p

Steady state tuber concentration of sucrose and glucose phosphates.

<p>A. Sucrose concentrations A: Example chromatogram indicating G1P and G6P peaks. B: G1P/G6P ratios. C: G1P concentrations. D: G6P concentrations. Error bars indicate standard error of measurement. The asterisk indicates metabolite levels significantly different for Kuras versus Desiree and Jutlandia (p-value<0.05). The determination of G1P/G6P is much more accurate than individual determination of G1P and G6P (see text for detail).</p