Improving Potato Tuber Quality and Production by Targeted Calcium Nutrition: the Discovery of Tuber Roots Leading to a New Concept in Potato Nutrition

Abstract

Calcium plays a major role in plant growth and development and in the maintenance and modulation of various cell functions, especially related to membrane structure and function and to cell wall structure. Calcium stabilizes cell membranes by bridging polar head groups of phospholipids at the membrane surface. Calcium is also an integral part of the cell wall where it provides stable intra-molecular linkages between pectin molecules, resulting in cell wall rigidity. A change in the cytosolic calcium concentration is also known to provide a cellular signal that regulates metabolism and mediates plant responses to stresses.Calcium deficiency is pervasive among fruit and tuber crops because calcium moves with water in the xylem and very little water moves to fruit and tuber tissues as compared to leaves. The water potential gradient within the potato plant favors xylem transport to the foliage since tubers are surrounded by moist soil. As a result, the calcium concentration is much higher in foliage than in the tuber. In our early work, we demonstrated that water and calcium taken up by the main root system bypass the tubers and are delivered to the above-ground portion of the plant, and roots arising from the stolons and tubers supply calcium to the tubers. Tuber calcium concentration can therefore be increased by selectively feeding tubers with calcium nutrients during tuber bulking period. The discovery of tuber roots has led to the development of a new concept in potato nutrition. We have demonstrated that in-season fertilization with calcium increases tuber calcium and lowers incidence of physiological disorders such as internal brown spot, hollow heart, and bruising. Localized tissue calcium deficiencies are implicated as mechanisms initializing cell death and tissue necrosis leading to internal brown spot and hollow heart in potatoes. There is also strong evidence for reducing storage rot by increasing tuber calcium. Finally, tuber calcium is important for the health of the sprout and of the tuber skin.

CAX1 Vacuolar Antiporter Overexpression in Potato Results in Calcium Deficiency in Leaves and Tubers by Sequestering Calcium as Calcium Oxalate

“…This suggests that sCAX1 transgenic lines may be affected by a decrease in apoplastic Ca 2+ . It is also interesting to note that hollow heart in potato is known to be caused by an abrupt increase in growth of the tuber tissue after a dry period (Palta, 2010). Our experiments measured cell wall biomass in tubers and found that there was ?1 g less dry weight of cell walls per 100 g of fresh tuber tissue in Atlantic and Russet Norkotah sCAX1 transgenic lines than in the control (Fig.…”

Effect of calcium soil amendments on phenolic compounds and soft rot resistance in potato tubers

“…Placement of calcium is important for enhancing calcium uptake by the tuber as the main root does not supply the tuber with calcium (Palta, 2010). Addition of calcium to the tuber and stolon areas can result in a threefold increase in calcium concentration in the tuber peel and medullary tissue (Kratzke and Palta 1986).…”

The epidemiology of Pectobacterium and Dickeya species and the role of calcium in postharvest soft rot infection of potato (Solanum tuberosum) caused by the pathogens: A review

“…Therefore to effectively increase tuber calcium supplemental calcium should be added during the tuber bulking stage because the tubers develop later in the season. Tubers have their own roots which take up water and calcium (Palta, 2010) and applications must be within reach of these tuber roots. An effective way of applying calcium is through fertigation (Westermann, 1993;Palta, 1996) while less soluble fertilizers can be applied by side dressing before the last hilling (Ozgen et al, 2006).…”

“…Increasing calcium concentration in the potato tubers helps reduce the incidence of tuber soft rot during storage, thereby increasing shelf life (Kratze and Palta, 1986;Palta, 2010). reported a correlation between tuber cell wall, calcium content and the level of resistance to soft rot while McGuire and Kelman (1983) found tuber calcium concentration to be high in the cortex and periderm.…”