Screening large numbers of genotypes for salinity tolerance in the field is difficult, due to spatial heterogeneity of soil chemical and physical properties, and to seasonal fluctations in rainfall. A field study in Syria using ICARDA’s advanced durum breeding lines indicated that significant genetic variation for salt tolerance might exist, but the confounding presence of drought stress made it difficult to identify genotypes with salt tolerance (Srivastava and Jana, 1984). They conclude that ‘the lack of reliable large-scale field screening techniques still seems to be the biggest problem in genetic improvement of salt and drought tolerance of crop plants’. Screening techniques that can be carried out under controlled environments have therefore often been used (Table 1).