CENTER OF ORIGIN (EVALUATION OF PLANT)
The concept of centres of origin was given by Vavilov based on his studies of a vast collection of plants at the institute of plant industry, Leningrad. N.I Vavilov proposed that crop plants evolved from wild species in the areas showing great diversity and termed them as primary centres of origin
. Later, crops moved to the other areas primarily due to the activities of the man. These areas generally lack the richness in variation found in the primary centres of origin. But in some areas, certain crop species show considerable diversity of forms although they did not originate there.
Such areas are known as secondary centres of origin of these species. Dominant genes characterize primary centres and secondary centres are characterized by a diversity of recessive character and are also devoid of wild relatives.
Law of homologous series in variation
Vavilov postulated this law of homologues series and this law states that characters found in one species also occur in other related species. In wheat diploid (2x), tetraploid (4x) and hexaploid (6x) wheats show a series of identical contrasting characters.
Similarly, genes secale duplicates the variation found in Triticum. Thus a character absent in a species, but found in a related species, is likely to be found in the collections of that species from the centre of its origin.
Main centres of origin proposed by Vavilov.
Central Asiatic Centre
Near Eastern centre
South Mexican and Central American centre.
South American centre