Abiotic stresses, plant reactions and new approaches towards understanding stress tolerance

摘要

Among abiotic factors a number of conditions are meaningful stresses because they can be life threatening and in combination determine the distribution of plants and the productivity of crops (Boyer, 1982). Prolonged drought, high or fluctuating salinity, and low and freezing temperatures account for most production losses, but flooding, high light, ozone, ion deficiency or imbalance, heavy metals and soil structure are other factors that threaten plant life. For example, various USDA statistical analyses identified drought as the single most yield-reducing factor. Yield reductions due to drought, high salinity and other abiotic factors amount to two-thirds of all losses, much more than the reduction due to pathogens. Despite considerable breedingefforts, breeding for tolerance to water deficit has not had much impact in the face of affordable irrigation, low commodity prices, and the globalization of trade (Flowers and Yeo, 1995). Various strategies have been employed for environmental stress tolerance breeding (Table 6.1), which can now be assisted by the inclusion of 'genomic' approaches.