| dc.description.abstract | Spinach (Spinacia oleracea) is an economically important leafy vegetable crop. Ascorbic acid (AsA), or vitamin C, is an essential nutrient for humans, involved in growth, development, and tissue repair. In plants, AsA functions as an antioxidant eliminating cell-damaging free radicals produced during normal metabolism or in response to stress. The increase of AsA content in model plants has resulted in abiotic stress tolerance. However, AsA content diversity in spinach germplasm is not well-known. In this study, we performed AsA quantification in a worldwide panel of 352 spinach accessions and determined that variability in AsA content in spinach germplasm is high and could be utilized for cultivar improvement. In addition, a genome-wide association study was performed using the Generalized linear model (GLM), compressed mixed linear model using P3D, and the perMarker model. A total of 490 SNPs resulted in significant marker-to-trait associations between all models. SNP markers were distributed in all six spinach chromosomes. Among the identified SNPs, only 27 were detected by all three models, commonly identified markers can be used as primary targets for validation. Identified candidate genes linked to the SNPs, did not include any known AsA biosynthesis pathway genes, suggesting that the observed AsA level differences may be related to substrate availability, the effect of plant hormones, or differences in transcriptional regulation. We also evaluated the effect of AsA on salt stress tolerance in ten spinach lines with low and high AsA contents. Plants were treated with a 150 mM NaCl solution. Stomatal conductance was higher in plants with high AsA content, showing a positive relationship when plants were under salt stress and higher chlorophyll fluorescence values independent of salt stress. These results suggest that AsA allows spinach plants to better tolerate salt stress by maintaining photosynthesis and respiration, although it was not reflected in a significant effect on biomass production at 150 mM NaCl. Finally, in silico analysis indicated that identified markers can differentiate between high and low AsA content accessions and that, upon validation, these markers should be useful for breeding programs. | en |
