Law of Parallel Variation
The concept of parallel variation also known as law of homologous series of variation was developed by Vavilov (1951) based on his study of crop diversity and centres of origin. Law of homologous series stated that a particular variation observed in a crop species is also expected to be available in its related species. For instance, if we get dwarf collections in one species of a crop, the same may be observed in another related species also. Vavilov used principle of homologous series of variation as a clue for discovering similar characters in related species.