Complementary Selection of Somatic Hybrids - The selection of somatic hybrids as a result of complementation by auxotrophic mutants may be useful as only the hybrid lines are expected to survive in the minimal medium. Auxotrophs are mutants requiring specific compounds for their growth. Glimelius et al. (1978) succeeded in selection of numerous somatic hybrids by utilizing protoplasts of nitrate reductase deficient and chlorate resistant mutant lines of tobacco.

Protoplasts of two genetically different mutants were fused and cultured in a ,medium containing nitrate as the sole nitrogen source. Parental protoplasts did not grow in the presence of nitrate, whereas fusion products regenerated. The complementation selection based on auxotrophic mutants, even though desirable and efficient, is very limited because of the limitation due to the paucity of higher plant auxotrophs.