Background Bread wheat is one of the most important crops for the human diet, but the increasing soil salinization is causing yield reductions worldwide. Improving salt stress tolerance in wheat requires the elucidation of the mechanistic basis of plant response to this abiotic stress factor. Although several studies have been performed to analyze wheat adaptation to salt stress, there are still some gaps to fully understand the molecular mechanisms from initial signal perception to the onset of responsive tolerance pathways. The main objective of this study is to exploit the dynamic salt stress transcriptome in underlying QTL regions to uncover candidate genes controlling salt stress tolerance in bread wheat. The massive analysis of 3′-ends sequencing protocol was used to analyze leave samples at osmotic and ionic phases. Afterward, stress-responsive genes overlapping QTL for salt stress-related traits in two mapping populations were identified. Results Among the over-represented salt-responsive gene categories, the early up-regulation of calcium-binding and cell wall synthesis genes found in the tolerant genotype are presumably strategies to cope with the salt-related osmotic stress. On the other hand, the down-regulation of photosynthesis-related and calcium-binding genes, and the increased oxidative stress response in the susceptible genotype are linked with the greater photosynthesis inhibition at the osmotic phase. The specific up-regulation of some ABC transporters and Na+/Ca2+ exchangers in the tolerant genotype at the ionic stage indicates their involvement in mechanisms of sodium exclusion and homeostasis. Moreover, genes related to protein synthesis and breakdown were identified at both stress phases. Based on the linkage disequilibrium blocks, salt-responsive genes within QTL intervals were identified as potential components operating in pathways leading to salt stress tolerance. Furthermore, this study conferred evidence of novel regions with transcription in bread wheat. Conclusion The dynamic transcriptome analysis allowed the comparison of osmotic and ionic phases of the salt stress response and gave insights into key molecular mechanisms involved in the salt stress adaptation of contrasting bread wheat genotypes. The leveraging of the highly contiguous chromosome-level reference genome sequence assembly facilitated the QTL dissection by targeting novel candidate genes for salt tolerance.

BACKGROUNDPotato frying quality is a complex trait influenced by sugar content in tubers. Good frying quality requires low content of reducing sugars to avoid the formation of dark pigments. Solanum tuberosum Group Phureja is a valuable genetic resource for breeding and for genetic studies. The sugar content after harvest was analyzed in a germplasm collection of Group Phureja to contribute to the understanding of the natural variation of this trait.RESULTSSucrose, glucose and fructose genotypic mean values ranged from 6.39 to 29.48 g kg−1 tuber dry weight (DW), from 0.46 to 28.04 g kg−1 tuber DW and from 0.29 to 27.23 g kg−1 tuber DW, respectively. Glucose/fructose and sucrose/reducing sugars ratios ranged from 1.01 to 6.67 mol mol−1 and from 0.15 to 7.78 mol mol−1, respectively. Five clusters of genotypes were recognized, three of them with few genotypes and extreme phenotypic values.CONCLUSIONSugar content showed a wide variation, representing the available variability useful for potato breeding. The results provide a quantitative approach to analyze the frying quality trait and are consistent with frying color. The analyzed germplasm presents extreme phenotypes, which will contribute to the understanding of the genetic basis of this trait. © 2016 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

A High Performance Liquid Chromatography (HPLC) method was developed and validated to quantify sucrose (non-reducing sugar), glucose, and fructose (reducing sugars) in raw tubers of Solanum tuberosum Group Phureja. Chromatographic analysis was performed using an AMINEX HPX 87H column, at 18 °C, linked to a refraction index detector, at 35 °C. The eluent was 10mM sulfuric acid. The conditions established for the method provided an optimum separation of sugars, citric acid, and malic acid, with resolution values higher or equal to one. Among the four sugar extraction methods tested, the double 50% (v/v) aqueous methanol extraction gave the highest level of analytes. Recovery of this extraction method ranged between 94.14 and 99.77%. The HPLC method was validated for repeatability, reproducibility, linearity, and limits of detection, and quantification. Relative standard deviation was found to be lower than five, when testing repeatability and reproducibility, which is suitable considering a range of acceptability from 5.3 to 7.3. Additionally, the regression analyses supported the method linearity in a range of quantification from 3 to 100 mg/L with regression coefficients values greater than 0.998 for the three analytes. Limits of detection were 3.0 mg/L for the three sugars and limits of quantification were 2.0 mg/L for sucrose and 3.0 mg/L for glucose and fructose. Four Colombian commercial cultivars (Criolla Guaneña, Criolla Paisa, Criolla Galeras, and Criolla Colombia) and five landrace accessions from the Colombian Core Collection of Group Phureja were grown in the district of Usme (Bogotá) fields to analyze their sugar contents. Sucrose, glucose, and fructose contents were found ranging from 0.93 to 3.11 g/100 g tuber dried weight (DW), from 0.25 to 4.53 g/100 g tuber DW, and from 0.10 to 1.49 g/100 g tuber DW, respectively. Therefore, a high range in the variability of sugar contents was found among genotypes. However, the variability was low among technical replicates of the same genotype, revealing an accurate quantification of sugars in Group Phureja. This method can be used to assess the amount of reducing and non-reducing sugars accumulation in potato germplasm.

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