Abstract
Key messageMost QTL for leaf sucrose content map to positions that are similar to positions of QTL for tuber starch content in diploid potato.In the present study, using a diploid potato mapping population and Diversity Array Technology (DArT) markers, we identified twelve quantitative trait loci (QTL) for tuber starch content on seven potato chromosomes: I, II, III, VIII, X, XI, and XII. The most important QTL spanned a wide region of chromosome I (42.0–104.6 cM) with peaks at 63 and 84 cM which explained 17.6 and 19.2 % of the phenotypic variation, respectively. ADP-glucose pyrophosphorylase (AGPase) is the key enzyme for starch biosynthesis. The gene encoding the large subunit of this enzyme, AGPaseS-a, was localized to chromosome I at 102.3 cM and accounted for 15.2 % of the variance in tuber starch content. A more than 100-fold higher expression of this gene was observed in RT-qPCR assay in plants with the marker allele AGPaseS-a1334. This study is the first to report QTL for sucrose content in potato leaves. QTL for sucrose content in leaves were located on eight potato chromosomes: I, II, III, V, VIII, IX, X and XII. In 5-week-old plants, only one QTL for leaf sucrose content was detected after 8 h of darkness; four QTL were detected after 8 h of illumination. In 11-week-old plants, 6 and 3 QTL were identified after dark and light phases, respectively. Of fourteen QTL for leaf sucrose content, eleven mapped to positions that were similar to QTL for tuber starch content. These results provide genetic information for further research examining the relationships between metabolic carbon molecule sources and sinks in potato plants.Electronic supplementary materialThe online version of this article (doi:10.1007/s00122-015-2615-9) contains supplementary material, which is available to authorized users.
Highlights
In plants, photosynthetic tissues are the main source of net carbon fixed in the Calvin-Benson cycle
Tuber starch content (TSC) values were normally distributed in the population 12–3 plants, except for in the year 2014, whereas leaf sucrose content (LSC) values deviated significantly from normality
Sucrose synthesized in photosynthetic tissues is exported to the other parts of the plant to support metabolism, storage, and growth
Summary
Photosynthetic tissues are the main source of net carbon fixed in the Calvin-Benson cycle. Triose-phosphate, the product of carbon assimilation, is converted to transitory starch in the chloroplast or transported to the cytosol, where sucrose biosynthesis takes place. Sucrose, being the major product of starch degradation, is exported from leaves to sink organs for storage, maintenance, and growth (Geigenberger 2011; Stitt and Zeeman 2012; Bahaji et al 2014). In growing potato (Solanum tuberosum L.) tubers, starch biosynthesis is the dominant pathway of carbohydrate metabolism (Geigenberger et al 2004). It is under control of many genetic and environmental factors. The first QTL analyses of specific gravity, an estimation of starch content, were conducted
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