Abstract
Potato (Solanum tuberosum) is a major crop world-wide and the productivity of currently used cultivars is strongly reduced at high soil salt levels. We compared the response of six potato cultivars to increased root NaCl concentrations. Cuttings were grown hydroponically and treated with 0 mM, 60 mM and 180 mM NaCl for one week. Growth reduction on salt was strongest for the cultivars Mozart and Mona Lisa with a severe senescence response at 180 mM NaCl and Mozart barely survived the treatment. The cultivars Desiree and Russett Burbank were more tolerant showing no senescence after salt treatment. A clear difference in Na+ homeostasis was observed between sensitive and tolerant cultivars. The salt sensitive cultivar Mozart combined low Na+ levels in root and stem with the highest leaf Na+ concentration of all cultivars, resulting in a high Na+ shoot distribution index (SDI) for Mozart as compared to Desiree. Overall, a positive correlation between salt tolerance and stem Na+ accumulation was found and the SDI for Na+ points to a role of stem Na+ accumulation in tolerance. In stem tissue, Mozart accumulated more H2O2 and less proline compared to the tolerant cultivars. Analysis of the expression of proline biosynthesis genes in Mozart and Desiree showed a clear reduction in proline dehydrogenase (PDH) expression in both cultivars and an increase in pyrroline-5-carboxylate synthetase 1 (P5CS1) gene expression in Desiree, but not in Mozart. Taken together, current day commercial cultivars show promising differences in salt tolerance and the results suggest that mechanisms of tolerance reside in the capacity of Na+ accumulation in stem tissue, resulting in reduced Na+ transport to the leaves.
Highlights
Accumulation of salts in soil has a negative effect on the production of a wide variety of crops
Based on the outcome of a pilot experiment with 10 cultivars grown as cuttings in agar medium with NaCl, tolerant and sensitive cultivars were selected for this study
To evaluate the salinity tolerance of these six cultivars, plants were propagated as cuttings for two weeks and grown on hydroponics (1/2 strength Hoagland) for three weeks, whereat during the last week of the experiment plants were exposed to three levels of salt (0 mM, 60 mM and 180 mM NaCl)
Summary
Accumulation of salts in soil has a negative effect on the production of a wide variety of crops. For various reasons the area of salt affected soils will rapidly expand in the near future. In view of the wealth of salt stress related studies on model plants and crops, there are relatively few studies that describe which traits remained in current potato cultivars that might be a starting point to improve tolerance of potato to salt. Potato is the fourth most cultivated crop world-wide and in (semi)arid areas where salt stress is a serious problem, productivity is considerably reduced. Wild potatoes growing under harsh conditions in the Andes are relatively stress tolerant, but extensive breeding and selection for traits other than abiotic stress tolerance have resulted in cultivars that are considered moderately salt tolerant [1] (FAO, 2010)
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