New Insights in Plant Breeding Efforts for Improved Salt Tolerance

I n nonhalophytic plants, saline conditions reduce vegetative growth and yields. Salt stress effects on plants from soil (≥4 dS·m–1 EC and 15% exchangeable Na+, plants require soluble Ca2+ fertilizers to remedy ionic imbalances, which adversely affect their growth and development. Selecting crops and cultivars that can tolerate saline conditions and may produce economically acceptable yields is very important. Plants in the same family, or even the same species, react differently to saline conditions. For example, in Cruciferae, the order from highest to lowest tolerance to balanced fertilizer salts was cabbage > cauliflower > broccoli > kohlrabi (Csizinszky, 1979), and, in Leguminosae, the order was green pea > faba bean > soybean > green bean (Delgado et al., 1994). In Solanaceae, differences to salt stress among tomato cultivars were reported by Perez-Alfocea et al. (1993) and among eggplant cultivars by Zurayk et al. (1993). Many plants have salt-sensitive stages during their development when irrigation by saline water should be avoided. Germinating seeds and young seedlings are particularly sensitive to salt stress, and irrigation with saline water during these stages is harmful. Hamdy et al. (1993) recommended irrigation with good-quality water during the salt-sensitive stages of growth, followed by saline water during later growth stages, when goodquality water may be scarce for irrigation purposes. Although consumptive use of water by agriculture and industry has declined since the mid-1980s, the demand for food, water, and land by an ever-growing population has increased (Solley, 1993; Suarez, 1992). Under these conditions, the knowledge of crop management on marginal lands, an understanding of irrigation management with brackish water, and crop selection for saline environmental conditions will increase in importance for horticulturists. In the following articles, some soil and crop management methods, breeding and selecting plants for salt tolerance, and aspects of water and solute transport in soils are discussed.