BP Singh

Centres of Origin and Diversity of Crop Plants 19where greater diversity occurs in species. Based on the presenceof great diversity,he identified 8 centres with three sub-centres asI centre of origin' where agriculture developed independently.Appendix-I lists the crop plant species that originated in thesecentres. These centres were found to be characterized by theaccumulation of dominant genes in the middle portion andrecessive genes in the periphery. This possibly led to the highconcentration of genetic diversity in the secondary centre ratherthan the primary centre of origin. The centres of diversity locatedby Vavilov have proved to be fertile promising collecting areas forfuture explorations. A well known hypothesis for the origin ofagriculture is the Rubbish-Heap hypothesis. It says that earlyhumans gathered roots and seeds for their food. Such plantsactively colonized the base areas around their dwellings, whichwere rich with the discarded rubbish.Vavilov also recognized secondary centres of origin andpainted out that valuable forms are found far removed fromprimary area of origin. A good example is the Washington Navel.~ra!!.g~ .. ~!~~