Current Knowledge in Physiological and Genetic Mechanisms Underpinning Tolerances to Alkaline and Saline Subsoil Constraints of Broad Acre Cropping in Dryland Regions

摘要: Abiotic stresses are a serious problem to crop production under dryland conditions in arid and semi-arid regions of the world. These abiotic include high low temperature, water deficit, salinity, sodicity, alkalinity, acidity ion deficiencies toxicities. Many Australian agricultural soils accumulate salts seasonal fluctuations have multiple subsoil constraints such as acidity, toxic ions (Rengasamy, 2006). Of these, salinity alkalinity simultaneously found southern Australia (Nuttall et al., 2003a; Nuttall 2003b). The simultaneous occurrence may result far greater productivity loss than any single or biotic factor. Nearly 800 million ha land throughout world is salt affected either by associated with sodicity (FAO, 2009). total area estimated be 32 arable permanent cropping 2000). Transient probably biggest factor causing (Figure 1; Rengasamy 2002). Saline generally defined those having concentrations soluble an electrical conductivity (ECe) more 4 dSm-1. Among salts, NaCl major component contributing (USSL, 2005). Yields important cereal, oilseed forage crops limited soil broad acre regions. Therefore, genetic improvement conventional nonconventional methods for tolerance vital maintain food production. ability grow reproduce saline differs widely between species, due differences control uptake from compartmentalise it effectively at cellular level (Munns & Tester, 2008). Crops grown on alkaline south-eastern potentially many factors, especially supply nutrition (Incerti O’Leary, 1990). Alkaline usually categorized availability plant nutrients, HCO3− CO32−, pH (Marschner, 1995; Misra Tyler, 1999). By definition, concentration alkalis neutralize acids (Bailey, 1996). Bicarbonate (HCO3−) carbonate (CO32–) principal