Abstract
Soil salinity is a major constrain to crop production and climate change accelerates it. It reduces plant water potential, causes ion imbalance, reduce plant growth and productivity, and eventually leads to death of the plant. This is the case in potato. However, potato has coping strategies such as accumulation of proline, an osmoregulator and osmoprotector. In addition, leaching of salts below the root zone is preferred, exogenous application of ascorbic acid and growth hormones are practiced to combat salinity. Breeding and genetic engineering also play key roles in salinity management of potato. Varieties such as: Amisk, BelRus, Bintje, Onaway, Sierra, and Tobique were tolerant in North America, variety Cara in Egypt, Sumi in Korea and varieties Vivaldi and Almera in Mediterranean region. Transgenic lines of Kennebec variety, lines S2 and M48 also proved tolerance due to transcription factor MYB4 encoded by rice Osmyb4 gene.
TopSoil Salinity
Salinity is a phenomenon that is causing major havoc in agricultural production (Figure 1) (D’Odorico et al., 2013). The earliest salinity effect in agriculture was recorded around 2400 to 1700 BC in the ancient Mesopotamia, currently Southern Iraq (Jacobsen & Adams, 1958). 6% of arable land around the world is affected by salinity or sodicity, this is 800 million hectares (FAO, 2009). Salt-affected soils have high levels of dissolved salts and or high concentrations of adsorbed sodium ions (Yadav et al., 2011). These soils are categorized into three classes: First are the saline soils having an electrical conductivity (EC) of over 4 dS m-1 and sodium adsorption ratio (SAR) of less than 13 or exchangeable sodium percentage (ESP) that is below 15. The second category are sodic soils which are characterized by an EC of less than 4 dS m-1, SAR or ESP above 13 and 15 respectively. Finally, the saline-sodic soils, whose EC, SAR, or ESP are above 4 dS m-1, 13 and 15 accordingly (United States Salinity Laboratory, 1954).
Figure 1. Global distribution of saline soils using data from the Harmonized World Soil Database. Salinity on the map is represented by electrical conductivity (dS m-1) and the coloring schemes illustrate different ranges in soil salinity corresponding to the relative degree to which soil salinity constrains plant productivity